Refrigeration System and Method

Abstract

To provide refrigeration systems suited for use with low GWP refrigerants.SOLUTION: Disclosed are cascaded refrigeration systems, comprising a plurality of refrigeration units, each refrigeration unit containing a first refrigeration circuit, each first refrigeration circuit comprising an evaporator and a heat exchanger, and a second refrigeration circuit; where each first circuit heat exchanger is arranged to transfer heat energy between its corresponding first refrigeration circuit and the second refrigeration circuit.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority of each of U.S. Provisional Application No. 62 / 522,836, filed Jun. 21, 2017, and U.S. Provisional Application No. 62 / 522,846, filed Jun. 21, 2017, each of which is incorporated herein by reference in its entirety.

[0002] (Field of the Invention) The present disclosure relates to refrigeration systems and methods, and more particularly, but not limited to, refrigeration systems suitable for use with low - GWP refrigerants.

Background Art

[0003] The refrigeration industry is increasingly being forced to replace high - global warming potential (GWP) refrigerants such as R404A with low - GWP refrigerants such as those having a GWP of less than 150, through regulatory changes and the like. This is particularly important in commercial refrigeration systems where large amounts of refrigerant are used.

[0004] One approach is to use low - GWP refrigerants such as carbon dioxide (R744) and hydrocarbon refrigerants. However, the approaches used heretofore can suffer from significant safety and financial drawbacks such as increased operating costs due to low system energy efficiency, high initial system costs due to high system complexity, high maintenance costs due to low system utility and reliability, and high flammability of the system. Systems containing highly flammable refrigerants according to conventional configurations can have low safety levels. ​​​​​​​​​​​​the fact that it may conflict with the constraints of regulatory regulations, and the liability of the operators and manufacturers of the refrigeration system is particularly inconvenient, especially by increasing the liability of the operators and manufacturers of the refrigeration system. Many of the refrigerators, freezers in supermarkets, and low-temperature display cases are publicly accessible and often operate in spaces with a high population density such as commercial refrigeration applications. Considering such commercial refrigeration applications, safety is particularly a concern .

[0005] Accordingly, the applicants understand that the refrigeration industry continues to require safe, robust, and sustainable methods for reducing the use of high GWP refrigerants that can be used by existing technologies .

[0006] One such method that has been used previously is shown in FIG. 1A. FIG. 1 shows a refrigeration system 100 commonly used for commercial refrigeration in a supermarket . System 10 0 is a direct expansion system that provides both medium-temperature refrigeration and low-temperature refrigeration via a medium-temperature refrigeration circuit 110 and a low-temperature refrigeration circuit 120 .

[0007] In a typical conventional configuration labeled 100 in FIG. 1A, the medium-temperature refrigeration circuit 11 0 has R134a as its refrigerant. The medium-temperature refrigeration circuit 110 provides both medium-temperature cooling and removes waste heat from the lower-temperature refrigeration circuit 120 via a heat exchanger 130 . The medium-temperature refrigeration circuit 110 extends between a roof 140, a machine room 141, and a sales floor 142 . On the other hand, the low-temperature refrigeration circuit 120 has R744 as its refrigerant. The low-temperature refrigeration circuit 120 extends between the machine room 141 and the sales floor 142 . Advantageously , as described above, R744 has a low GWP

[0008] However, although a refrigeration system of the type disclosed in FIG. 1A may be capable of providing a good efficiency level, the applicants understand that such a system has at least two major drawbacks, namely, firstly, that such a system uses the high GWP refrigerant R134a ( R134a having a GWP of about 1300), and secondly, that even when the low temperature part of such a system uses the low GWP refrigerant R744, this refrigerant exhibits a number of the above-mentioned drawbacks, including significant safety and financial drawbacks. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0009] The present invention includes a cascade refrigeration system, the cascade refrigeration system including a plurality of first refrigeration circuits, each first refrigeration circuit including a first refrigerant that is flammable and a compressor having a horsepower rating of about 2 horsepower (about 1.5 kilowatts) or less (a measure of the electrical power input to the compressor), a heat exchanger in which the first refrigerant condenses, and a plurality of first refrigeration circuits; a second refrigeration circuit containing a second refrigerant that is non-flammable; and an evaporator in which the second refrigerant evaporates at a temperature below the condensation temperature of the first refrigerant, the second refrigerant evaporating in the heat exchanger by absorbing heat from the first refrigerant.

[0010] The present invention includes a cascade refrigeration system, the cascade refrigeration system including a plurality of low temperature refrigeration circuits, each first low temperature refrigeration circuit including a flammable first refrigerant and a compressor having a horsepower rating of about 2 horsepower or less, and the first refrigerant condensing in a temperature range of about -5°C to about -15°C ​ A plurality of low-temperature refrigeration circuits including a heat exchanger that contracts, and a non-flammable medium-temperature refrigerant is contained therein A medium-temperature refrigeration circuit, and an evaporator in which the above medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the above low-temperature refrigerant and in the range of about -5°C to about -15°C, and the above medium-temperature refrigerant absorbs heat from the above low-temperature refrigerant An evaporator that evaporates in the above heat exchanger by doing so, and is provided.

[0011] As used herein, the term "flammable" with respect to a refrigerant means that the refrigerant does not fall into Category A1 under the ASHRAE34-2016 test protocol that defines the conditions and equipment and uses the current method ASTM E681-09 annex A1. Therefore, refrigerants that are classified as A2L or more flammable than the A2L classification under the ASHRAE34-2016 test protocol that defines the conditions and equipment and uses the current method ASTM E681-09 annex A1 are considered flammable. Conversely, the term "non-flammable" with respect to a refrigerant means that the refrigerant is classified as A1 under the ASHRAE34-2016 test protocol that defines the conditions and equipment and uses the current method ASTM E681-09 annex A1.

[0012] As used herein, the term "medium-temperature refrigeration" refers to a refrigeration circuit in which the refrigerant circulating in the circuit evaporates at a temperature of about -5°C to about -15°C, preferably at a temperature of about -10°C.

[0013] As used herein, the term "about" when used with respect to temperature is to be understood to mean a variation of ± 3°C at the specified temperature. The refrigerant circulating in the medium-temperature circuit can evaporate at a temperature of -10°C ±2°C or -10°C ±1°C. ​​​​​​

[0014] The medium-temperature refrigeration of the present invention can be used, for example, to cool products such as dairy products, deli meats, and fresh foods. The individual temperature levels of different products are adjusted based on product requirements. The low-temperature refrigeration is typically provided at an evaporation level of about -25°C. As used herein, the term "low-temperature refrigeration" refers to a refrigeration circuit in which the refrigerant circulating within the circuit evaporates at a temperature of about -20°C to about -30°C, preferably at a temperature of about -25°C. The refrigerant circulating within the low-temperature circuit can evaporate at a temperature of -25°C ± 2°C or -25°C ± 1°C.

[0015] The low-temperature refrigeration of the present invention can be used, for example, to cool products such as ice cream and frozen products. Here too, the individual temperature levels of different products are adjusted based on product requirements.

[0016]

[0017] The present invention also includes a cascade refrigeration system, which includes a plurality of low-temperature refrigeration circuits, each including a combustible first refrigerant, a compressor having a power rating of about 2 horsepower or less, and a heat exchanger in which the first refrigerant condenses in the temperature range of about -5°C to about -15°C, and each of the low-temperature refrigeration circuits is housed in a separate low-temperature refrigeration unit; a medium-temperature refrigeration circuit containing a non-combustible medium-temperature refrigerant; and an evaporator in which the medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C, and the medium-temperature refrigerant absorbs heat from the low-temperature refrigerant and evaporates in the heat exchanger.

[0018] The present invention also includes a cascade refrigeration system, which comprises a plurality of low-temperature refrigeration circuits, a flammable low-temperature refrigerant, and a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C. The plurality of low-temperature refrigeration circuits, a medium-temperature refrigeration circuit containing a non-flammable medium-temperature refrigerant, and an evaporator in which the above medium-temperature refrigerant evaporates at a temperature below the above low-temperature refrigerant condensation temperature and in a range of about -5°C to about -15°C. The heat exchanger is a flooded heat exchanger in which the above medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the above low-temperature refrigerant. It comprises an evaporator.

[0019] As used herein, the term "flooded heat exchanger" refers to a heat exchanger that evaporates a liquid refrigerant to produce refrigerant vapor without substantially any superheat. As used herein, the term "without substantially any superheat" means that the vapor leaving the evaporator is at a temperature not exceeding 1°C above the boiling temperature of the liquid refrigerant in the heat exchanger.

[0020] The present invention also includes a cascade refrigeration system, which comprises a plurality of low-temperature refrigeration circuits, a flammable low-temperature refrigerant, and a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C. The plurality of low-temperature refrigeration circuits, each of which is housed in a separate low-temperature refrigeration unit, a medium-temperature refrigeration circuit containing a non-flammable medium-temperature refrigerant, and the heat exchanger, wherein the above medium-temperature refrigerant has a temperature below the above low-temperature refrigerant condensation temperature. An evaporator that evaporates within a temperature range of about -5°C to about -15°C, and the heat exchanger described above is the flooded heat exchanger in which the medium-temperature refrigerant described above evaporates by absorbing heat from the low-temperature refrigerant described above. It includes a medium-temperature refrigeration circuit that is

[0021] The present invention also includes a cascade refrigeration system, and this cascade refrigeration system has a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit containing at least about 50% by weight, or at least about 75% by weight, or at least 95% by weight, or at least 99% by weight of HFO-1 234yf, transHFO-1234ze, or a combination thereof, a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the low-temperature refrigerant described above condenses within a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration circuits, and a non-combustible medium-temperature refrigeration circuit containing a medium-temperature refrigerant, and the heat exchanger described above has an evaporator in which the medium-temperature refrigerant described above evaporates within a temperature range below the condensation temperature of the low-temperature refrigerant described above and within a range of about -5°C to about -15°C. The medium-temperature refrigerant described above evaporates in the heat exchanger described above by absorbing heat from the low-temperature refrigerant described above. It includes a medium-temperature refrigeration circuit.

[0022] The present invention also includes a cascade refrigeration system, and this cascade refrigeration system has a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit containing at least about 50% by weight, or at least about 75% by weight, or at least 95% by weight, or at least 99% by weight of HFO-1 234yf, transHFO-1234ze, or a combination thereof, a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the low-temperature refrigerant described above condenses within a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration circuits and a medium-temperature refrigerant​​ A medium-temperature refrigeration circuit containing the above, wherein the above medium-temperature refrigerant is non-flammable, and the above heat exchange device is equipped with an evaporator in which the above medium-temperature refrigerant evaporates within a temperature range below the condensation temperature of the above low-temperature refrigerant and from about -5°C to about -15°C. The above medium-temperature refrigerant absorbs heat from the above low-temperature refrigerant and evaporates within the above heat exchanger, and is equipped with a medium-temperature refrigeration circuit.

[0023] The present invention also includes a cascade refrigeration system, which comprises a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit containing at least about 50% by weight, or at least about 75% by weight, or at least 95% by weight, or at least 99% by weight of HFO-1 234yf, transHFO-1234ze, or a combination thereof, a flammable low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above low-temperature refrigerant condenses within a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration circuits, and a medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the above medium-temperature refrigerant is non-flammable, and the above heat exchange device is equipped with an evaporator in which the above medium-temperature refrigerant evaporates within a temperature range below the condensation temperature of the above low-temperature refrigerant and from about -5°C to about -15°C. The above medium-temperature refrigerant absorbs heat from the above low-temperature refrigerant and evaporates within the above heat exchanger, and is equipped with a medium-temperature refrigeration circuit.

[0024] The present invention also includes a cascade refrigeration system, which comprises a plurality of low-temperature refrigeration circuits, a flammable low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above low-temperature refrigerant condenses within a temperature range of about -5°C to about -15°C. The plurality of low-temperature refrigeration circuits are provided, and a medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the above medium-temperature refrigerant is non-flammable, and the above heat exchange ​The refrigerant is non-flammable, and the heat exchanger includes an evaporator in which the medium-temperature refrigerant evaporates at a temperature lower than the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The heat exchanger is a flooded heat exchanger in which the medium-temperature refrigerant evaporates within the heat exchanger by absorbing heat from the low-temperature refrigerant. The medium-temperature refrigeration circuit includes such a flooded heat exchanger. In a preferred embodiment, the second circuit, preferably the medium-temperature circuit, can be arranged substantially completely outside the plurality of first refrigeration units, preferably outside the plurality of low-temperature circuits. As used herein, the term "substantially completely outside" means that the components of the second refrigeration circuit are not within the first refrigeration unit, except that a delivery pipe or the like that can be regarded as a part of the second refrigeration circuit may enter the first refrigeration unit to provide heat exchange between the refrigerants of the first and second refrigeration circuits. As used herein, the terms "first refrigeration unit" and "low-temperature refrigeration unit" refer to a structure that is at least partially closed or closable and can provide cooling inside at least a part of the structure, and is structurally distinct from any structure that wholly surrounds or houses the second refrigeration circuit. Consistent with and in accordance with such meaning, the preferred first refrigeration circuit and low-temperature refrigeration circuit of the present invention are referred to as "built-in" herein when housed within such a first (preferably low-temperature) refrigeration unit in accordance with the meaning described herein. The second refrigeration circuit may further include a fluid receiver.

[0025] In a preferred embodiment, the second circuit, preferably the medium-temperature circuit, can be arranged substantially completely outside the plurality of first refrigeration units, preferably outside the plurality of low-temperature circuits. As used herein, the term "substantially completely outside" means that the components of the second refrigeration circuit are not within the first refrigeration unit, except that a delivery pipe or the like that can be regarded as a part of the second refrigeration circuit may enter the first refrigeration unit to provide heat exchange between the refrigerants of the first and second refrigeration circuits. As used herein, the terms "first refrigeration unit" and "low-temperature refrigeration unit" refer to a structure that is at least partially closed or closable and can provide cooling inside at least a part of the structure, and is structurally distinct from any structure that wholly surrounds or houses the second refrigeration circuit. Consistent with and in accordance with such meaning, the preferred first refrigeration circuit and low-temperature refrigeration circuit of the present invention are referred to as "built-in" herein when housed within such a first (preferably low-temperature) refrigeration unit in accordance with the meaning described herein. The second refrigeration circuit may further include a fluid receiver. In a preferred embodiment, the second circuit, preferably the medium-temperature circuit, can be arranged substantially completely outside the plurality of first refrigeration units, preferably outside the plurality of low-temperature circuits. As used herein, the term "substantially completely outside" means that the components of the second refrigeration circuit are not within the first refrigeration unit, except that a delivery pipe or the like that can be regarded as a part of the second refrigeration circuit may enter the first refrigeration unit to provide heat exchange between the refrigerants of the first and second refrigeration circuits. As used herein, the terms "first refrigeration unit" and "low-temperature refrigeration unit" refer to a structure that is at least partially closed or closable and can provide cooling inside at least a part of the structure, and is structurally distinct from any structure that wholly surrounds or houses the second refrigeration circuit. Consistent with and in accordance with such meaning, the preferred first refrigeration circuit and low-temperature refrigeration circuit of the present invention are referred to as "built-in" herein when housed within such a first (preferably low-temperature) refrigeration unit in accordance with the meaning described herein. The second refrigeration circuit may further include a fluid receiver.

[0026] As used herein, the terms "first refrigeration unit" and "low-temperature refrigeration unit" refer to a structure that is at least partially closed or closable and can provide cooling inside at least a part of the structure, and is structurally distinct from any structure that wholly surrounds or houses the second refrigeration circuit. Consistent with and in accordance with such meaning, the preferred first refrigeration circuit and low-temperature refrigeration circuit of the present invention are referred to as "built-in" herein when housed within such a first (preferably low-temperature) refrigeration unit in accordance with the meaning described herein. The second refrigeration circuit may further include a fluid receiver. In a preferred embodiment, the second circuit, preferably the medium-temperature circuit, can be arranged substantially completely outside the plurality of first refrigeration units, preferably outside the plurality of low-temperature circuits. As used herein, the term "substantially completely outside" means that the components of the second refrigeration circuit are not within the first refrigeration unit, except that a delivery pipe or the like that can be regarded as a part of the second refrigeration circuit may enter the first refrigeration unit to provide heat exchange between the refrigerants of the first and second refrigeration circuits. As used herein, the terms "first refrigeration unit" and "low-temperature refrigeration unit" refer to a structure that is at least partially closed or closable and can provide cooling inside at least a part of the structure, and is structurally distinct from any structure that wholly surrounds or houses the second refrigeration circuit. Consistent with and in accordance with such meaning, the preferred first refrigeration circuit and low-temperature refrigeration circuit of the present invention are referred to as "built-in" herein when housed within such a first (preferably low-temperature) refrigeration unit in accordance with the meaning described herein. The second refrigeration circuit may further include a fluid receiver. In a preferred embodiment, the second circuit, preferably the medium-temperature circuit, can be arranged substantially completely outside the plurality of first refrigeration units, preferably outside the plurality of low-temperature circuits. As used herein, the term "substantially completely outside" means that the components of the second refrigeration circuit are not within the first refrigeration unit, except that a delivery pipe or the like that can be regarded as a part of the second refrigeration circuit may enter the first refrigeration unit to provide heat exchange between the refrigerants of the first and second refrigeration circuits. As used herein, the terms "first refrigeration unit" and "low-temperature refrigeration unit" refer to a structure that is at least partially closed or closable and can provide cooling inside at least a part of the structure, and is structurally distinct from any structure that wholly surrounds or houses the second refrigeration circuit. Consistent with and in accordance with such meaning, the preferred first refrigeration circuit and low-temperature refrigeration circuit of the present invention are referred to as "built-in" herein when housed within such a first (preferably low-temperature) refrigeration unit in accordance with the meaning described herein.

[0027] The second refrigeration circuit may further include a fluid receiver.

[0028] Each first refrigeration circuit may be incorporated within its respective refrigeration unit.

[0029] Each refrigeration unit may be disposed in a first area. The first area may be the shop floor. This means that each first refrigeration circuit (preferably a low-temperature refrigeration circuit) may also be disposed within any first area on the shop floor.

[0030] Each refrigeration unit may include a space and / or an object contained within the space to be cooled, preferably, the space is inside the refrigeration unit. Each evaporator may be preferably arranged to cool its respective space / object by cooling the air within the space to be cooled.

[0031] As described above, the second refrigeration circuit, and preferably the medium-temperature refrigeration circuit, may have its components extending between the first refrigeration unit (preferably the low-temperature refrigeration unit) and the second area. The second area may be, for example, a machine room that houses a substantial portion of the components of the second refrigeration circuit.

[0032] The second refrigeration circuit (preferably the medium-temperature refrigeration unit) may extend to the second and third areas. The third area may be an area outside the building or building in which the first refrigeration unit and the second area are located. This enables the use of ambient cooling.

[0033] Unless otherwise indicated herein for a particular embodiment, the refrigerant in each of the first refrigeration circuits may be different from or the same as the other refrigerants within the first refrigeration circuit, and each may also be different from or the same as the refrigerant within the second refrigeration circuit.

[0034] ​​​​​​​​​​​ Unless otherwise indicated herein for a particular embodiment, the refrigerant of the first refrigeration circuit and / or the refrigerant of the second refrigeration circuit may have a low global warming potential (GWP).

[0035] Unless otherwise indicated herein for a particular embodiment, the refrigerant of the first refrigeration circuit and / or the refrigerant of the second refrigeration circuit may have a GWP of less than 150. This is enabled by each first refrigeration circuit provided within each refrigeration unit respectively .

[0036] Unless otherwise indicated herein for a particular embodiment, the refrigerant of the second refrigeration circuit is classified as A1 under ASHRAE 34 (measured by ASTM E681) or may be non-flammable, classified as A2L under ASHRAE 34 (measured by ASTM E681). Since the second refrigeration circuit can be very long and can extend between different areas of a building, for example, between a shop floor (where a refrigeration unit may be deployed) and a machine room, this may be desirable. Thus, having a flammable refrigerant within the second refrigeration circuit can be dangerous due to both the risk of leakage and the potential severity of a leak, as the second refrigeration circuit covers a wider area and thus exposes more people and / or structures to the risk of fire .

[0037] The refrigerant of the first refrigeration circuit may be flammable. This may be practically at least partially acceptable since each first refrigeration circuit provided within each refrigeration unit respectively has a relatively low power compressor (plural acceptable) housed therein .

[0038] ​Each first refrigeration circuit may include at least one fluid expansion device. At least one of the fluid expansion devices may be a capillary tube or an orifice tube. This is enabled by the conditions imposed on each first refrigeration circuit due to the relatively constant nature of its corresponding refrigeration unit. This means that simpler flow control devices, such as capillary tubes and orifice tubes, may preferably be used, or are preferably used, for use in the first refrigeration circuit.

[0039] The average temperature of each first refrigeration circuit may be lower than the average temperature of the second refrigeration circuit. This is because the second refrigeration circuit may be used to provide cooling for the first refrigeration circuit, i.e., to remove heat from the first refrigeration circuit, and each first refrigeration circuit may cool the space to be cooled within its corresponding refrigeration unit.

[0040] The second refrigeration circuit may cool each of the first refrigeration circuits, i.e., remove heat from each of the first refrigeration circuits.

[0041] Each heat exchanger may be arranged to transfer thermal energy at the corresponding circuit interface position between its corresponding first refrigeration circuit and the second refrigeration circuit.

[0042] The second refrigeration circuit may include a second evaporator. The second evaporator may be connected in parallel with the circuit interface position.

[0043] Each of the circuit interface positions may be connected in a series-parallel combination with each of the other circuit interface positions. Advantageously, this means that the circuit interface positions, When a defect or interruption is detected in one of the first refrigeration circuit or the first refrigeration unit , the location, circuit, or unit where the defect occurs can be isolated and / or bypassed by the second refrigeration circuit so that the defect does not spread within the system.

[0044] Each of the circuit interface positions may be connected in series with at least one other circuit interface position.

[0045] Each of the circuit interface positions may be connected in series with each of the other circuit interface positions.

[0046] Each of the circuit interface positions may be connected in parallel with at least one other circuit interface position.

[0047] Each of the circuit interface positions may be connected in parallel with each of the other circuit interface positions.

[0048] The second refrigerant, preferably a medium-temperature refrigerant, may include a mixed refrigerant. The mixed refrigerant may include R515A .

[0049] The R515A refrigerant is non-flammable. This refrigerant is useful because the second refrigerant circuit (preferably a medium-temperature refrigerant ) can cover a number of areas, and as a result, having a non-flammable refrigerant is important for reducing the severity of potential leaks.

[0050] In other embodiments, the non-flammable refrigerant may include HFO-1233zd(E), or may include at least about 50%, or at least 75%, or may consist essentially of, or consist of, HFO-1233 zd(E).

[0051] The first refrigerant (preferably a low-temperature refrigerant) used in the first refrigerant circuit (preferably a low-temperature refrigeration circuit) may include any one of R744, C3-C4 hydrocarbons, R1234yf, R1234ze(E), R 455A, and combinations thereof. The hydrocarbon may include any one of R29 0, R600a, or R1270. These refrigerants have a low GWP .

[0052] The second refrigeration circuit may further include a compressor

[0053] The second refrigeration circuit may include a ambient cooling branch including a compressor and a compressor branch . This means that the compressor branch may be bypassed. The benefit of bypassing the compressor branch is that when the ambient conditions are sufficiently cold for the second refrigerant, the compressor stage can be bypassed so that sufficient cooling is provided by the ambient air .

[0054] The ambient cooling branch may be connected in parallel with the compressor branch. The parallel configuration allows the compressor branch to be bypassed by the second refrigerant

[0055] The ambient cooling branch may be exposed to the external ambient temperature. This is for cooling the second refrigerant at the location of the compressor stage .

[0056] The ambient cooling branch may extend outside one or more buildings including a first region

[0057] The refrigerant entering the ambient cooling branch can be cooled by the ambient air temperature when the ambient air temperature is lower than the temperature of the refrigerant entering the ambient cooling branch .

[0058] ​​The ambient cooling branch may be connected in series with the pump.

[0059] The valve may be provided at one or both of the junctions between the ambient cooling branch and the compressor branch to control the flow of refrigerant in each of the ambient cooling branch and the compressor branch. This enables controlling whether to utilize the compressor branch and / or the ambient cooling branch and how much to utilize them.

[0060] The positions of the pump, additional evaporator, and circuit interface may be arranged between one or more valves.

Brief Description of the Drawings

[0061] Here, an exemplary configuration of the present disclosure will be described with reference to the drawings.

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 4A

Figure 5A

Figure 5B

Figure 6

[0062] ​ Throughout this specification, the same reference numerals refer to the same components.

DETAILED DESCRIPTION OF THE INVENTION

[0063] Comparative Example To assist those skilled in the art in understanding the refrigeration circuits of the present disclosure and their respective advantages, a brief description of the function of the refrigeration system is provided with respect to the comparative refrigeration system shown in FIGS. 1A and 1B. is provided.

[0064] FIG. 1B shows an embodiment of a refrigeration system 100 for comparison with the further systems described below. The system 100 includes an intermediate-temperature refrigeration circuit 110 and a low-temperature refrigeration circuit 120.

[0065] The low-temperature refrigeration circuit 120 includes a compressor 121, an interface having a heat exchanger 130 for discharging heat to ambient conditions, an expansion valve 122, and an evaporator 123. The low-temperature refrigeration circuit 120 interacts with the intermediate-temperature refrigeration circuit 110 through an inter-circuit heat exchanger 150, and this inter-circuit heat exchanger discharges heat from the low-temperature refrigerant to the intermediate-temperature refrigerant, thereby serving to generate subcooled refrigerant liquid within the low-temperature refrigerant cycle. The evaporator 123 interacts with a space to be cooled, such as inside a refrigerated compartment. The components of the low-temperature refrigeration circuit are connected in the order of the evaporator 123, compressor 1 21, heat exchanger 130, inter-circuit heat exchanger 150, and expansion valve 122. The components are connected together via a pipe 124 that contains the low-temperature refrigerant.

[0066] The intermediate-temperature refrigeration circuit 110 includes a compressor 111, a condenser 113 for discharging heat to ambient conditions, and a fluid receiver 114. The liquid intermediate-temperature refrigerant from the receiver 114 passes through an expansion valve 112. and manifolded to flow to each of 118, and thus two parallel-connected branches, namely, the subcooled low-temperature branch 117 downstream of the expansion device 118, and the medium-temperature cooling branch 116 downstream of the expansion device 112 are provided. The low-temperature subcooled branch includes an inter-circuit heat exchanger that provides subcooling to the low-temperature circuit as described above. The medium-temperature cooling branch 116 includes a medium-temperature evaporator 119 that interacts with a space to be cooled, such as inside a refrigerated compartment.

[0067] The medium-temperature refrigerant is a high-GWP refrigerant (e.g., R134a). R134a is a hydrofluoro carbon (HFC). R134a is non-flammable and provides a good coefficient of performance.

[0068] System 100 spans three areas of a building, namely, the roof where condensers 113 and 130 are located, the machine room where compressors 111, 112, heat exchanger 150, receiving tank 114, and expansion devices 118 are located, and the sales floor 142 where each of the LT case, MT case, and their respective expansion devices are located. Thus, the low-temperature refrigeration circuit 120 and the medium-temperature refrigeration circuit 110 each extend between the sales floor, the machine room, and the roof. In use, the medium-temperature circuit 110 provides medium-temperature cooling to the space cooled via evaporator 119, and the low-temperature circuit 120 provides low-temperature cooling to the space cooled via evaporator 123. The medium-temperature circuit 110 also removes heat from the liquid condensate from the low-temperature condenser 120, resulting in subcooling of the liquid entering evaporator 123. Here, the individual and overall functions of the various components of the low-temperature refrigeration circuit 120 are described.

[0069] ​​​​​​​​​​ Starting from the heat exchanger 150, the heat exchanger 130 is a device suitable for transferring heat between a low-temperature refrigerant and a medium-temperature refrigerant. In one example, the heat exchanger 150 is a shell-and-tube type heat exchanger. Other types of heat exchangers, such as plate heat exchangers and those of other designs, may also be used. During use, the medium-temperature refrigerant absorbs heat from the low-temperature refrigerant, thus cooling the low-temperature refrigerant. The removal of heat through this heat exchanger 150 will supercool the liquid low-temperature refrigerant from the subcooling condenser 130. After subcooling, the low-temperature refrigerant flows through the liquid line of pipe 12 4 to the expansion valve 122. The role of the expansion valve 122 is to reduce the pressure of the low-temperature refrigerant. By doing so, since pressure and temperature are proportional, the temperature of the low temperature refrigerant decreases accordingly. Then, the low-temperature and low-pressure refrigerant either flows or is pumped to the evaporator 123. The evaporator 123 is used to transfer heat to the low-temperature refrigerant from the space to be cooled, such as a low-temperature refrigeration case in a supermarket ket. That is, in the evaporator 123, the liquid refrigerant receives heat from the space to be cooled and evaporates into a gas at that time. After the evaporator 123, the gas is drawn into the compressor 121 through the intake line of pipe 124 by the compressor 121. When it reaches the compressor 121, the low-pressure and low-temperature gas refrigerant is compressed. This raises the temperature of the refrigerant. Therefore, the refrigerant is converted from a low-temperature and low-pressure gas to a high-temperature and high-pressure gas. The high-temperature and high-pressure gas is released into the discharge pipe of pipe 124 and proceeds to the heat exchanger (condenser) 130, where, in the manner described above the gas is condensed into a liquid. This specifically describes the operation of the low-temperature refrigeration circuit 120, but the principles described here can generally be applied to refrigeration cycles.

[0070] Here, the individual and overall functions of the various components of the medium-temperature refrigeration circuit 110 will be described. Starting from the heat exchanger 150, as described above, the medium-temperature refrigerant absorbs heat from the low-temperature refrigerant through the heat exchanger 150. Due to this heat absorption, the refrigerant in the medium-temperature circuit 150, which is a low-temperature gas and / or a mixture of gas and liquid when entering the heat exchanger 150, has its liquid changed to the gas phase and / or, when generating superheat, has the temperature of the gas increased. When exiting the heat exchanger 150, the gaseous refrigerant is sucked into the compressor 111 (together with the refrigerant from the evaporator 119) and compressed by the compressor 111 into a high-temperature and high-pressure gas. This gas is discharged into the pipe 115 and, in this embodiment, moves to the condenser 113 disposed on the roof of the building. In the condenser 113, the gaseous medium-temperature refrigerant releases heat to the external ambient air, and as a result, is cooled and condensed into a liquid. After the condenser 113, the liquid refrigerant accumulates in the fluid receiver 114. In this example, the fluid receiver 114 is a tank. When exiting the fluid receiver 114, the liquid refrigerant is manifolded to the medium-temperature branch 116 and the subcooling branch 117 connected in parallel. In the medium-temperature branch 116, the liquid refrigerant flows to the expansion valve 112 used to reduce the pressure, and thus the temperature, of the liquid refrigerant. Then, the relatively low-temperature liquid refrigerant enters the heat exchanger 119 and absorbs heat from the space to be cooled, which interacts with the evaporator 119f. In the subcooling branch 117, the liquid refrigerant similarly first flows to the expansion valve 118 that reduces the pressure and temperature of the refrigerant. After the valve 118, the refrigerant flows to the inter-circuit heat exchanger 150 as described above. From there, the gaseous refrigerant from the heat exchanger is sucked into the compressor 111 by the compressor 111. ​​​​​​​​​​​​​​It is introduced and rejoins the refrigerant from the medium-temperature cooling branch 116.

[0071] Although not as described above, in order to function as intended, when entering the heat exchanger 150 the temperature of the refrigerant in the medium-temperature circuit 110 must be lower than the temperature of the refrigerant in the low-temperature circuit 120 when entering the heat exchanger 150. Obviously, if it is not the case, the medium-temperature circuit 110 will not provide the desired subcooling to the low-temperature refrigerant in the circuit 120.

[0072] The above describes the operation of a comparative embodiment of the refrigeration system 100, as illustrated in FIG. 1B. The refrigeration principle described with respect to FIG. 1B can be equally well applied to other refrigeration systems of the present disclosure.

[0073] Summary of the Preferred Embodiment Some refrigeration systems according to preferred embodiments of the present invention are described below. Each system has several refrigeration units, and each of the refrigeration units has at least one dedicated refrigeration circuit disposed therein. That is, each refrigeration unit includes at least one refrigeration circuit.

[0074] The refrigeration circuit included in the refrigeration unit may include at least a heat exchanger that removes heat from the refrigerant in the circuit and an evaporator that adds heat to the refrigerant.

[0075] The refrigeration circuit included in the refrigeration unit may include a compressor, and at least (preferably by removing heat from the refrigerant vapor exiting the compressor) a heat exchanger that removes heat from the refrigerant in the circuit, and an evaporator that adds heat to the refrigerant (preferably by cooling the cooling area of the refrigeration unit). and may include. The Applicants have found that the size of the compressor used within the preferred first refrigeration circuit (and preferably the low temperature refrigeration circuit) of the present invention is important for achieving at least some of the highly advantageous and unexpected results of the preferred embodiments of the present invention. In particular, each compressor within the circuit has been found to preferably be a small compressor. As used herein, the term "small compressor" means that the compressor has a power rating of about 2 horsepower or less. When used herein, the term "small compressor" means that the compressor has a power rating of about 2 horsepower or less. When used herein with respect to the compressor power rating, this value is determined by the input power rating of the compressor. When used with respect to the compressor horsepower rating, "about" means the indicated horsepower ± 0.5 horsepower. The compressor size may preferably be from 0.1 horsepower to about 2 horsepower, or from 0.1 horsepower to about 1 horsepower in the preferred embodiments. The compressor size may be from 0.1 horsepower to a maximum of 0.75 horsepower, or from 0.1 horsepower to a maximum of 0.5 horsepower.

[0076] The refrigeration unit may be an integrated physical entity, i.e., an entity not designed to be disassembled into components. The refrigeration unit may be, for example, a refrigerator or freezer. It will be understood that more than one refrigeration circuit (especially including more than one low temperature refrigeration circuit) may be included within each refrigeration unit (preferably including each low temperature refrigeration unit). It will be understood that more than one refrigeration circuit (especially including more than one low temperature refrigeration circuit) may be included within each refrigeration unit (preferably including each low temperature refrigeration unit).

[0077] The refrigeration circuit provided within each refrigeration unit may itself be cooled at least in part by a common refrigeration circuit that is external to the refrigeration unit. In contrast to the dedicated refrigeration circuits housed within each refrigeration unit, the common refrigeration circuit (generally referred to herein as the second and third refrigeration circuits) is located between the sales floor (where the refrigeration units are located) and the machine room, etc. machine room, etc. A building that houses units, such as between a single room and / or a roof or an outer area There may be a wide - ranging circuit extending between a plurality of areas.

[0078] Each refrigeration unit may include at least one compartment for storing goods, such as perishable goods. The compartment may define a space cooled by a refrigeration circuit housed inside the refrigeration unit.

[0079] Cascade refrigeration system An embodiment of the refrigeration system according to the present invention is schematically illustrated in FIG. 2 and will be described in detail below.

[0080] FIG. 2 shows a cascade refrigeration system 200. More specifically, FIG. 2 shows a refrigeration system 200 having three first refrigeration circuits 220a, 220b, and 220c. Each of the first refrigeration circuits 220a, 220b, 220c has an evaporator 223, a compressor 221 , a heat exchanger 230, and an expansion valve 222. Each of the compressor, evaporator, and heat exchanger in the circuit is illustrated by a single icon, but it is understood that the compressor, evaporator, heat exchanger, expansion valve, etc. may each include a plurality of such units. In each of the circuits 220a, 220b, and 220c, the evaporator 223, the compressor 221, the heat exchanger 230, and the expansion valve 222 are connected in series with each other in the listed order. Each of the first refrigeration circuits 220a, 220b, and 220c is contained inside a separate respective refrigeration unit (not shown). In this example, each of the three refrigeration units is a refrigerator unit, and the refrigerator unit houses its corresponding first refrigeration circuit. ​​In this way, each refrigeration unit includes a built-in dedicated refrigeration circuit. The refrigeration unit (not shown), and thus the first refrigeration circuits 220a, 220b, 220c are disposed on the sales floor 242 of the supermarket

[0081] In this embodiment, the refrigerant in each of the first refrigeration circuits 220a, 220b, 220c is a low-GWP refrigerant such as R744, C3-C4 hydrocarbons (R290, R600a, R1270), R123 4yf, R1234ze(E), or R455A. As will be understood by those skilled in the art, the refrigerant in each of the first refrigeration circuits 220a, 220b, 220c may be the same as or different from the refrigerant in each of the other first refrigeration circuits 220a, 220b, 220c

[0082] The refrigeration system 200 also has a second refrigeration circuit 210. The second refrigeration circuit 210 has a compressor 211, a condenser 213, and a fluid receiver 214. The compressor 211, the condenser 213, and the fluid receiver 214 are connected in series in a given order. Each of the compressor, condenser, fluid receiver, etc. in the second circuit is illustrated by a single icon, but it will be understood that the compressor, evaporator, heat exchanger, expansion valve, etc. may each include a plurality of such units The second refrigeration circuit 210 also has four parallel-connected branches, namely, three medium-temperature cooling branches 217a, 217b, and 217c, and one low-temperature cooling branch 216. The four parallel-connected branches 217a 217b, 217c, and 216 are connected between the fluid receiver 214 and the compressor 211is. Each of the medium-temperature cooling branches 217a, 217b, and 217c has an expansion valve 21 8a, 218b, and 218c, and an evaporator 219a, 219b, and 219c, respectively has. The expansion valves 218 and the evaporators 219 are connected in series in a given order between the fluid receiver 214 and the condenser 211 The low-temperature cooling branch 216 has an expansion valve 212 and a second refrigerant is led to and withdrawn from each of the heat exchangers 230a, 230b, 230c of the first refrigeration circuits 220a, 220b, 220c in the form of inlet and outlet pipes, conduits, valves, etc (collectively represented as 260a, 260b, and 260c respectively), an interface -face. The low-temperature cooling branch 216 has a corresponding circuit interface with each of the heat exchangers 230a, 230b, 230c of the first refrigeration circuits 220a, 220 b, 220c at the corresponding circuit interface positions 231a, 231b, 231c to interact. Each circuit interface position 231a, 231b, 231c is arranged in a combination of directly parallel with each of the other circuit interface positions 231a, 231b, 231c

[0083] The medium-temperature refrigeration circuit 210 has components extending between the sales floor 242, the machine room 241, and the roof 14 0. The low-temperature cooling branch 216 and the medium-temperature cooling branches 217a, 217b, 217c of the medium-temperature refrigeration circuit 210 are located on the sales floor 242 The compressor 211 and the fluid receiver 214 are located within the machine room 241. The condenser 2 13 is located in a place where it can be easily exposed to ambient conditions, such as on the roof 240 In this embodiment, the refrigerant of the medium-temperature refrigeration circuit 210 is a mixture containing R515A. R

[0084] ​The 515A consists essentially of about 88 wt% hydrofluoroolefin (HFO) 1234ze(E) and about 12 wt% HFC227ea (heptafluoropropane), and preferably consists of these refrigerants. Advantageously, the mixture provides a non-flammable refrigerant with improved safety. More advantageously, the mixture has a low GWP that makes this mixture an environmentally friendly solution.

[0085] The use of the preferred embodiment illustrated in Figure 2 can be summarized as follows. - Each of the first refrigeration circuits 220a, 220b, 220c absorbs heat through its evaporator 223 to provide low-temperature cooling to a space (not shown) to be cooled, - The second refrigeration circuit 210 absorbs heat from each of the heat exchangers 230a, 230b, 230c to cool the first refrigeration circuits 220a, 220b, 220c, - The second refrigeration circuit 210 absorbs heat in each of its evaporators 219 to provide medium-temperature cooling to a space (not shown) to be cooled,

[0086] Using the configuration of the invention of the type shown in Figure 2, in particular, since each first refrigeration circuit 230 is built into the corresponding refrigeration unit, several beneficial results can be achieved.

[0087] For example, the installation and removal of the refrigeration unit and the overall cascaded refrigeration system 200 are simplified. This is because a refrigeration unit having built-in first refrigeration circuits 220a, 220b, 220c can be easily connected or disconnected from the second refrigeration circuit 210 without the need for modifications to the first refrigeration circuits 220, 220b, 220 c. c. This is because it can be done. In other words, the refrigeration unit can be simply "plugged in and unplugged" with respect to the second refrigeration circuit 210. It can be "plugged in and unplugged".

[0088] Another advantage is that each refrigeration unit can be factory-tested by default before being installed in the live refrigeration system 200, including the corresponding first refrigeration circuits 220a, 220b, 220c. This reduces the possibility of defects, including potential leakage of harmful refrigerants. Therefore, a reduced leakage rate can be achieved. This reduces the possibility of defects, including potential leakage of harmful refrigerants. Therefore, a reduced leakage rate can be achieved. This reduces the possibility of defects, including potential leakage of harmful refrigerants. Therefore, a reduced leakage rate can be achieved.

[0089] Another advantage is that since each of the circuits 220a, 220b, 220c is installed within its corresponding refrigeration unit and does not extend between a series of units, the length of the first refrigeration circuits 220a, 220b, 220c can be shortened. The shortened circuit length can result in improved efficiency because there is less heat ingress in shorter lines due to the reduced surface area. Additionally, the shortened circuit length can also result in a reduced pressure drop, thereby improving the efficiency of the system 200. The shortened circuit length can result in improved efficiency because there is less heat ingress in shorter lines due to the reduced surface area. Additionally, the shortened circuit length can also result in a reduced pressure drop, thereby improving the efficiency of the system 200. The shortened circuit length can result in improved efficiency because there is less heat ingress in shorter lines due to the reduced surface area. Additionally, the shortened circuit length can also result in a reduced pressure drop, thereby improving the efficiency of the system 200. The shortened circuit length can also result in a reduced pressure drop, thereby improving the efficiency of the system 200. The shortened circuit length can also result in a reduced pressure drop, thereby improving the efficiency of the system 200.

[0090] Providing a shortened circuit length and circuits built into each refrigeration unit also allows the applicants to use more flammable refrigerants, such as R744, hydrocarbons (R290, R600a, R1270), R1234yf, R1234ze(E ), or R455A, which the applicants have found to be a very beneficial result. This is due to the reduced likelihood of refrigerant leakage (as described above), and at the same time, even if the refrigerant leaks, the leak is contained within a relatively small area and the containment area of the corresponding refrigeration unit. ), or R455A, which the applicants have found to be a very beneficial result. This is due to the reduced likelihood of refrigerant leakage (as described above), and at the same time, even if the refrigerant leaks, the leak is contained within a relatively small area and the containment area of the corresponding refrigeration unit. ), or R455A, which the applicants have found to be a very beneficial result. This is due to the reduced likelihood of refrigerant leakage (as described above), and at the same time, even if the refrigerant leaks, the leak is contained within a relatively small area and the containment area of the corresponding refrigeration unit. (as described above), which is due to the reduced likelihood of refrigerant leakage, and at the same time, even if the refrigerant leaks, the leak is contained within a relatively small area and the containment area of the corresponding refrigeration unit. (as described above), which is due to the reduced likelihood of refrigerant leakage, and at the same time, even if the refrigerant leaks, the leak is contained within a relatively small area and the containment area of the corresponding refrigeration unit. it will be contained, and since the size of the unit is small, only a relatively small amount of refrigerant filling will be used This is because. In addition, this configuration results in a relatively small, limited, and uniform area containing potentially flammable materials, thus enabling relatively low-cost fire mitigation contingency procedures and / or the use of devices This is because. In addition, this configuration results in a relatively small, limited, and uniform area containing potentially flammable materials, thus enabling relatively low-cost fire mitigation contingency procedures and / or the use of devices and / or the use of the device. Such more flammable refrigerants may have a lower global warming potential (GWP). Therefore, advantageously, the government and social goals regarding the use of low-GWP refrigerants can be met without compromising the safety of the system and potentially even exceeded Another advantage is that each of the first refrigeration circuits 220a, 220b, 220c can cool only its corresponding refrigeration unit This means that the load on each of the first refrigeration circuits 220a, 220b, 220c can remain relatively constant. That is, constant conditions are applied to the condensation stage 231 and the evaporation stage 223 of the first refrigeration circuit 220

[0091] This enables the simplification of the design of the first refrigeration circuit 220 in that a passive expansion device 222 such as a capillary tube or an orifice tube can be used This is in contrast to more complex circuits that require the use of electronic expansion devices and thermostatic expansion valves Since the use of such complex devices is avoided, the cost can be reduced and the reliability can be increased This enables the simplification of the design of the first refrigeration circuit 220 in that a passive expansion device 222 such as a capillary tube or an orifice tube can be used This is in contrast to more complex circuits that require the use of electronic expansion devices and thermostatic expansion valves Since the use of such complex devices is avoided, the cost can be reduced and the reliability can be increased This is in contrast to more complex circuits that require the use of electronic expansion devices and thermostatic expansion valves Since the use of such complex devices is avoided, the cost can be reduced and the reliability can be increased Furthermore, importantly, by providing a flooded heat exchanger in the second refrigeration circuit according to such an embodiment, the heat transfer between the first circuit and the second circuit is improved. Therefore

[0092] Furthermore, importantly, by providing a flooded heat exchanger in the second refrigeration circuit according to such an embodiment, the heat transfer between the first circuit and the second circuit is improved. Therefore the efficiency of the overall refrigeration system is improved the efficiency of the overall refrigeration system is improved

[0093] There are several advantages that can result from the circuit interface positions being connected in parallel with other circuit interface positions. One advantage is that a defect associated with or occurring at one circuit interface position does not affect other circuit interface positions, so elasticity can be provided within the system. This is due to each circuit interface position being served by a corresponding branch of the second refrigeration circuit. Another advantage is that the temperature of the second refrigerant can be kept relatively constant before each circuit interface position, so the heat transfer efficiency between the first refrigeration circuit and the second refrigeration circuit can be improved. In contrast, when two circuit interface positions are connected in series, the temperature of the refrigerant in the second refrigeration circuit can be higher before the downstream circuit interface position than before the upstream circuit interface position. Overall, providing a plurality of first refrigeration circuits according to the present invention, each disposed within its respective refrigeration unit, preferably disposed as a built-in refrigeration circuit, has the benefits of reducing the leakage rate, simplifying the entire refrigeration system, otherwise enabling the use of dangerous low-GWP refrigerants, improving maintenance and installation, and reducing pressure drop, etc., leading to an improvement in system efficiency. In particular, from the perspective of the points described herein, the present invention includes a cascade refrigeration system, the cascade refrigeration system including a plurality of first refrigeration circuits, each first refrigeration circuit being combustible and having a first refrigerant with a GWP of about 150 or less and about 2 horsepower or less, and a second refrigerant having a GWP of about 1500 or less and about 20 horsepower or less, and a heat exchanger disposed between the first refrigeration circuit and the second refrigeration circuit. When two circuit interface positions are connected in series, the temperature of the refrigerant in the second refrigeration circuit can be higher before the downstream circuit interface position than before the upstream circuit interface position. In contrast, when two circuit interface positions are connected in series, the temperature of the refrigerant in the second refrigeration circuit can be higher before the downstream circuit interface position than before the upstream circuit interface position. In contrast, when two circuit interface positions are connected in series, the temperature of the refrigerant in the second refrigeration circuit can be higher before the downstream circuit interface position than before the upstream circuit interface position.

[0094] Overall, providing a plurality of first refrigeration circuits according to the present invention, each disposed within its respective refrigeration unit, preferably disposed as a built-in refrigeration circuit, has the benefits of reducing the leakage rate, simplifying the entire refrigeration system, otherwise enabling the use of dangerous low-GWP refrigerants, improving maintenance and installation, and reducing pressure drop, etc., leading to an improvement in system efficiency. In particular, from the perspective of the points described herein, the present invention includes a cascade refrigeration system, the cascade refrigeration system including a plurality of first refrigeration circuits, each first refrigeration circuit being combustible and having a first refrigerant with a GWP of about 150 or less and about 2 horsepower or less, and a second refrigerant having a GWP of about 1500 or less and about 20 horsepower or less, and a heat exchanger disposed between the first refrigeration circuit and the second refrigeration circuit. Overall, providing a plurality of first refrigeration circuits according to the present invention, each disposed within its respective refrigeration unit, preferably disposed as a built-in refrigeration circuit, has the benefits of reducing the leakage rate, simplifying the entire refrigeration system, otherwise enabling the use of dangerous low-GWP refrigerants, improving maintenance and installation, and reducing pressure drop, etc., leading to an improvement in system efficiency.

[0095] In particular, from the perspective of the points described herein, the present invention includes a cascade refrigeration system, the cascade refrigeration system including a plurality of first refrigeration circuits, each first refrigeration circuit being combustible and having a first refrigerant with a GWP of about 150 or less and about 2 horsepower or less, and a second refrigerant having a GWP of about 1500 or less and about 20 horsepower or less, and a heat exchanger disposed between the first refrigeration circuit and the second refrigeration circuit. and a second refrigerant having a GWP of about 1500 or less and about 20 horsepower or less, and a heat exchanger disposed between the first refrigeration circuit and the second refrigeration circuit. A compressor having the rated horsepower, and a heat exchanger in which the first refrigerant condenses as described above, and a plurality of of the first refrigeration circuits, a second refrigeration circuit containing a non-flammable second refrigerant, and the above An evaporator in which the second refrigerant evaporates at a temperature lower than the condensation temperature of the first refrigerant, and the above The second refrigerant evaporates in the heat exchanger by absorbing heat from the first refrigerant , and an evaporator.

[0096] In particular, from the perspective of the points described in this specification, the present invention also includes a cascade refrigeration system This cascade refrigeration system is a plurality of first refrigeration circuits, and each first The refrigeration circuit is a first refrigerant that is flammable and has a GWP of about 150 or less, and about 2 horsepower A compressor having a rated horsepower of less than or equal to the following, and a heat exchanger in which the first refrigerant condenses as described above, A plurality of first refrigeration circuits, a second refrigerant that is non-flammable and has a GWP of at most about 500 Containing a second refrigeration circuit, and the second refrigerant described above is less than the condensation temperature of the first refrigerant An evaporator that evaporates at a temperature, and the second refrigerant described above absorbs heat from the first refrigerant By doing so, it evaporates in the heat exchanger, and an evaporator.

[0097] The present invention includes a cascade refrigeration system, and this cascade refrigeration system is a plurality Of low-temperature refrigeration circuits, each first low-temperature refrigeration circuit is flammable and about 150 or less A first refrigerant having a GWP, a compressor having a rated horsepower of about 2 horsepower or less, and the above first A heat exchanger in which the refrigerant condenses in a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration Circuits, a medium-temperature refrigeration circuit containing a non-flammable medium-temperature refrigerant, and the above medium-temperature refrigerant is the above low-temperature An evaporator that evaporates in a temperature range below the refrigerant condensation temperature and in a range of about -5°C to about -15°C, wherein the medium-temperature refrigerant described above absorbs heat from the low-temperature refrigerant described above and evaporates in the heat exchanger described above. An evaporator, comprising:

[0098] The present invention includes a cascade refrigeration system, and this cascade refrigeration system includes a plurality of low-temperature refrigeration circuits, each first low-temperature refrigeration circuit being combustible and having a GWP of about 150 or less, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the first refrigerant described above condenses in a temperature range of about -5°C to about -15°C, a plurality of low-temperature refrigeration circuits, a medium-temperature refrigeration circuit containing a non-combustible medium-temperature refrigerant having a GWP of up to about 500, and an evaporator in which the medium-temperature refrigerant described above evaporates at a temperature below the low-temperature refrigerant condensation temperature and in a range of about -5°C to about -15°C, and in which the medium-temperature refrigerant described above absorbs heat from the low-temperature refrigerant described above and evaporates in the heat exchanger described above.

[0099] In a preferred embodiment, the present invention also includes a cascade refrigeration system, and this cascade refrigeration system includes a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit having a GWP of about 150 or less and containing at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the low-temperature refrigerant described above condenses in a temperature range of about -5°C to about -15°C, a plurality of low-temperature refrigeration circuits. ​​​A road and a medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the medium-temperature refrigerant is non-flammable. , a medium-temperature refrigeration circuit, and an evaporator in which the medium-temperature refrigerant evaporates in a temperature range below the condensation temperature of the low-temperature refrigerant and from about -5°C to about -15°C, wherein the medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. The evaporator is provided.

[0100] In a preferred embodiment, the present invention also includes a cascade refrigeration system. This cascade type refrigeration system is a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit having a GWP of about 150 or less and containing at least about 50% by weight, or at least about 75% by weight, or at least about 95% by weight, or at least 99% by weight of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C. A plurality of low-temperature refrigeration circuits are provided. A medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the medium-temperature refrigerant is non-flammable and has a GWP of at most about 500. A medium-temperature refrigeration circuit, and an evaporator in which the medium-temperature refrigerant evaporates in a temperature range below the condensation temperature of the low-temperature refrigerant and from about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. The evaporator is provided.

[0101] In a preferred embodiment, the present invention also includes a cascade refrigeration system. This cascade type refrigeration system is a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit having a GWP of about 150 or less having a GWP of, and at least about 50 wt%, or at least about 75 wt%, or at least at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a flammable cryogenic refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the cryogenic refrigerant condenses in a temperature range of about -5°C to about -15°C, a plurality of cryogenic refrigeration circuits, and an intermediate-temperature refrigeration circuit containing an intermediate-temperature refrigerant, wherein the intermediate-temperature refrigerant has a GWP of up to about 500, and at least about 50 wt%, or at least about 75 wt%, or at least at least 85 wt% of R1234ze(E), an intermediate-temperature refrigeration circuit that is non-flammable, and the intermediate-temperature refrigerant evaporates at a temperature below the condensation temperature of the cryogenic refrigerant and in a range of about -5°C to about -15°C, an evaporator in which the intermediate-temperature refrigerant absorbs heat from the cryogenic refrigerant and evaporates in the heat exchanger described above.

[0102] In a preferred embodiment, the present invention also includes a cascade refrigeration system, the cascade refrigeration system being a plurality of cryogenic refrigeration circuits, each cryogenic refrigeration circuit having a GWP of about 150 or less and at least about 50 wt%, or at least about 75 wt%, or at least at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a flammable cryogenic refrigerant, a compressor having a work output of about 3.5 kilowatts or less, and a heat exchanger in which the cryogenic refrigerant condenses in a temperature range of about -5°C to about -15°C, a plurality of A low-temperature refrigeration circuit and an intermediate-temperature refrigeration circuit containing an intermediate-temperature refrigerant, wherein the intermediate-temperature refrigerant has a maximum GWP of about 500 and contains at least about 50 wt%, or at least about 75 wt%, or at least 85 wt% of R1234ze(E) and about 10 wt% to about 15 wt% of R227ea, and is non-flammable. The intermediate-temperature refrigeration circuit and an evaporator in which the intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. It has a GWP of up to about 500 and contains at least about 50 wt%, or at least about 75 wt%, or at least 85 wt% of R1234ze(E) and about 10 wt% to about 15 wt% of R227ea. It contains at least about 50 wt%, or at least about 75 wt%, or at least 85 wt% of R1234ze(E) and about 10 wt% to about 15 wt% of R227ea. A non-flammable intermediate-temperature refrigeration circuit and an evaporator in which the intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. An evaporator that evaporates in the range of a temperature below the condensation temperature of the low-temperature refrigerant and about -5°C to about -15°C, and the intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. The intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. It includes an evaporator.

[0103] In a preferred embodiment, the present invention also includes a cascade refrigeration system. The cascade refrigeration system includes a plurality of low-temperature refrigeration circuits. Each low-temperature refrigeration circuit has a GWP of about 150 or less and contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. It also includes a compressor with a horsepower rating of about 2 hp or less, a heat exchanger in which the low-temperature refrigerant condenses in the temperature range of about -5°C to about -15°C, a plurality of low-temperature refrigeration circuits, an intermediate-temperature refrigeration circuit containing an intermediate-temperature refrigerant, the intermediate-temperature refrigerant has a maximum GWP of about 500 and contains about 88 wt% of R1234ze(E) and about 12 wt% of R227ea, and is non-flammable. The intermediate-temperature refrigeration circuit and an evaporator in which the intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. It has a GWP of about 150 or less and contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. It contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. It contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. It contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. A flammable low-temperature refrigerant, a compressor with a horsepower rating of about 2 hp or less, and a heat exchanger in which the low-temperature refrigerant condenses in the temperature range of about -5°C to about -15°C. The low-temperature refrigerant condenses in the temperature range of about -5°C to about -15°C. An intermediate-temperature refrigeration circuit containing an intermediate-temperature refrigerant, the intermediate-temperature refrigerant has a maximum GWP of about 500 and contains about 88 wt% of R1234ze(E) and about 12 wt% of R227ea, and is non-flammable. The intermediate-temperature refrigeration circuit and an evaporator in which the intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. It has a GWP of about 500 and contains about 88 wt% of R1234ze(E) and about 12 wt% of R227ea. It contains about 88 wt% of R1234ze(E) and about 12 wt% of R227ea. An evaporator in which the intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The intermediate-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. comprises.

[0104] In a preferred embodiment, the present invention also includes a cascade refrigeration system, and this cascade refrigeration system is a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit having a GWP of about 150 or less and containing at least about 50 wt%, or at least about 75 wt%, or at least about 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 hp or less, and a heat exchanger in which the above low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration circuits; a medium-temperature refrigeration circuit containing a medium-temperature refrigerant, the medium-temperature refrigerant having a GWP of at most about 500 and containing at least about 70 wt% of R1234ze(E), R1234yf or combinations thereof, a non-combustible medium-temperature refrigeration circuit; and an evaporator in which the above medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the above low-temperature refrigerant and in a range of about -5°C to about -15°C such that the above medium-temperature refrigerant absorbs heat from the above low-temperature refrigerant and evaporates in the above heat exchanger , comprising an evaporator.

[0105] In a preferred embodiment, the present invention also includes a cascade refrigeration system, and this cascade refrigeration system is a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit having a GWP of about 150 or less and containing at least about 50 wt%, or at least about 75 wt%, or at least about 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof A combustible cryogenic refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and the above cryogenic cold A heat exchanger in which the medium condenses in a temperature range of about -5°C to about -15°C, and a plurality of cryogenic refrigeration cycles A medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the medium-temperature refrigerant has a maximum GWP of about 500 And contains at least about 70% by weight of R1234ze(E), R1234yf , or a combination thereof, and further contains one Or two or more of R1233zd(E) and CF3I, a non-flammable, medium-temperature refrigeration circuit, and the above medium-temperature refrigerant is the above cryogenic refrigerant An evaporator that evaporates at a temperature below the condensation temperature and in the range of about -5°C to about -15°C, and the above The medium-temperature refrigerant evaporates in the above heat exchanger by absorbing heat from the above cryogenic refrigerant. An evaporator, and is provided with.

[0106] Cascade refrigeration system - alternative As will be understood by those skilled in the art in view of the teachings contained herein, any number of first refrigeration Circuits 220 may be present. In particular, the same number of first refrigeration circuits 2 20 may be present as the number of refrigeration units to be cooled. Thus, the second refrigeration circuit 210 may interact with any number of first refrigeration circuits 220.

[0107] As will be apparent to those skilled in the art in view of the teachings contained herein, any number and configuration Of medium-temperature cooling branches 217 and evaporators 218 may be present.

[0108] In an alternative configuration, each first refrigeration circuit 220 may be arranged completely In parallel with each other first refrigeration circuit 220. An embodiment of such a configuration is shown in FIG. 3. FIG. 3 shows each circuit interface Face positions 231a, 231b, 231c, and each other circuit interface position 231 231a, 231b, and 231c are shown in full parallel arrangement. The components of 300 are otherwise identical to those of system 200 (described with reference to FIG. 2). and the components of system 300 function in substantially the same manner as system 200. However, the overall system performance and other important features of the overall system may differ from this configuration. It will be appreciated that the results may be significantly affected by changes in composition.

[0109] Usefully, only a given portion of the refrigerant from the second refrigeration circuit 210 is returned to the compressor 211. The heat exchanger 230 is the first to pass through the first heat exchanger 230. This configuration is therefore similar to the serial configuration. In addition, a portion of the refrigerant preheated by passing through the upstream heat exchanger is received by either heat exchanger. 2, ensuring that each of the heat exchangers 230 receives the second refrigerant at approximately the same temperature. to.

[0110] As will be apparent to one skilled in the art in view of the teachings contained herein, the first and second cooling Many of the circuit interface locations 231a, 231b, 231c with respect to the cooling circuit 210 Other configurations may be achieved and are indeed envisioned.

[0111] As will be apparent to those skilled in the art in view of the teachings contained herein, preferred modules include: By using the first refrigeration circuit design of the valve type, the refrigeration system of the preferred embodiment of the present invention is In the refrigeration circuit 210, it is possible to use a non-flammable low-pressure refrigerant having a relatively low GWP. Furthermore, the preferred system of the present invention is a flammable gas having a low GWP in the first refrigeration circuit. This has resulted in the unexpected result of relatively safe and efficient use of low pressure refrigerants, , reduce the influence on the surroundings, and provide a refrigeration system having excellent environmental characteristics, excellent safety mechanisms, and improved system efficiency.

[0112] Cascade refrigeration system having a flooded evaporator The preferred refrigeration system of the present invention will be illustrated and described here with reference to FIG. 4.

[0113] FIG. 4 schematically shows a cascade refrigeration system 400 having a second refrigeration circuit 410 with a receiver for delivering a second refrigerant of a liquid that causes the operation of the flooded evaporator in the first refrigeration circuit. More specifically, FIG. 4 shows a refrigeration system 400 having two first refrigeration circuits 420a, 420b. Each of the first refrigeration circuits 420a, 420b has an evaporator 4 23, a compressor 421, a heat exchanger 430, and an expansion valve 422. In each of the circuits 420 a, 420b, the evaporator 423, the compressor 421, the heat exchanger 430, and the expansion valve 42 2 are connected in series with each other in the listed order. Each of the first refrigeration circuits 420a, 420b is provided within its respective refrigeration unit (not shown). In this embodiment, each refrigeration unit is a refrigerator unit, and the refrigerator unit houses its respective first refrigeration circuit. In this way, a built-in dedicated refrigeration circuit is provided for each refrigeration unit. The refrigeration unit (not shown), and thus the first refrigeration circuits 420a, 420b, are arranged on the sales floor 462 of a supermarket. In this embodiment, the refrigerant in the first refrigeration circuits 420a, 420b is R744, hydrocarbon (R290, R600a, R1270), R1234yf, R1234ze(E), or

[0114] (R290, R600a, R1270), R1234yf, R1234ze(E), or It is a low-GWP refrigerant such as R455A. As would be understood by those skilled in the art, the refrigerant in each of the first refrigeration circuits 420a and 420b may be the same as or different from the refrigerant in each of the other first refrigeration circuits 420a and 420b. The refrigeration system 400 also has a second refrigeration circuit 410. The second refrigeration circuit 410 has a compressor branch 450 and a ambient cooling branch 451. The compressor branch 450 is connected in parallel with the ambient cooling branch 451. The compressor branch 450 has a compressor 411, a condenser 413, an expansion valve 418, and a receiver 414. The compressor 411, the condenser 413, and the expansion valve 418 are connected in series in a given order. The receiver 414 is connected between the inlet of the compressor 411 and the outlet of the expansion valve 418. The ambient cooling branch 451 has a chiller 452.

[0115] The compressor branch 450 and the ambient cooling branch 451 are connected in parallel by a first controllable valve 440 and a second controllable valve 441. The controllable valves 440 and 441 are controllable so as to control the amount of refrigerant flowing through each of the compressor branch 450 and the ambient cooling branch 451. The first control valve 440 is connected in series with a pump 442. The second refrigeration circuit 410 also has two additional branches connected in parallel with each other, namely, an intermediate temperature cooling branch 417 and a low temperature cooling branch 416. The intermediate temperature cooling branch 417 and the low temperature cooling branch 416 are between the pump 442 and the second controllable valve 441. The compressor branch 450 is connected in parallel with the ambient cooling branch 451.

[0116] The compressor branch 450 has a compressor 411, a condenser 413, an expansion valve 418, and a receiver 414. The compressor 411, the condenser 413, and the expansion valve 418 are connected in series in a given order. The receiver 414 is connected between the inlet of the compressor 411 and the outlet of the expansion valve 418. The ambient cooling branch 451 has a chiller 452. The compressor 411, the condenser 413, and the expansion valve 418 are connected in series in a given order. The receiver 414 is connected between the inlet of the compressor 411 and the outlet of the expansion valve 418. The ambient cooling branch 451 has a chiller 452.

[0117] The compressor branch 450 and the ambient cooling branch 451 are connected in parallel by a first controllable valve 440 and a second controllable valve 441. The controllable valves 440 and 441 are controllable so as to control the amount of refrigerant flowing through each of the compressor branch 450 and the ambient cooling branch 451. The first control valve 440 is connected in series with a pump 442. The compressor branch 450 and the ambient cooling branch 451 are connected in parallel by a first controllable valve 440 and a second controllable valve 441. The controllable valves 440 and 441 are controllable so as to control the amount of refrigerant flowing through each of the compressor branch 450 and the ambient cooling branch 451.

[0118] The second refrigeration circuit 410 also has two additional branches connected in parallel with each other, namely, an intermediate temperature cooling branch 417 and a low temperature cooling branch 416. The intermediate temperature cooling branch 417 and the low temperature cooling branch 416 are between the pump 442 and the second controllable valve 441. The intermediate temperature cooling branch 417 and the low temperature cooling branch 416 are between the pump 442 and the second controllable valve 441. are connected therebetween.

[0119] The medium-temperature cooling branch 417 has an evaporator 419. The low-temperature cooling branch 416 interacts with the heat exchangers 430a, 430b of the first refrigeration circuits 420a, 420b at the respective circuit interface positions 431a, 431b. Each of the circuit interface positions 431a, 431b is a combination in direct series-parallel with the other circuit interface positions 431a, 431b.

[0120] The second refrigeration circuit 410 includes components that extend the circuit between the sales floor 462, the machine room 461, and the roof 44 0. The low-temperature cooling branch 416 and the medium-temperature cooling branch 417 of the medium-temperature refrigeration circuit 410 are preferably mainly arranged on the sales floor 462. Mainly arranged on the sales floor 462 means that the circuit positions 431a, 431b and the evaporator 4 19 are arranged on or very close to the sales floor 462. However, the junction between the low-temperature cooling branch 416 and the intermediate cooling branch 417, and some of the pipes of the low-temperature cooling branch 416 and the intermediate cooling branch 417 are arranged in the machine room 461. However, the junction between the low-temperature cooling branch 416 and the intermediate cooling branch 417, and some of the pipes of the low-temperature cooling branch 416 and the intermediate cooling branch 417 are arranged in the machine room 461. within.

[0121] The compressor branch 450 includes components that extend the branch between the machine room 461 and the roof 460. More specifically, the compressor 411, the expansion valve 418, and the flooded receiver 414 are arranged in the machine room 461. The condenser 413 is arranged in a place where easy access to the ambient air is possible, such as on the roof 460. 414 are arranged in the machine room 461. The condenser 413 is arranged in a place where easy access to the ambient air is possible, such as on the roof 460. where easy access to the ambient air is possible.

[0122] The ambient cooling branch 450 extends the branch between the machine room 461 and the roof 460. It includes the components to be caused. The chiller 452 is also placed in a location such as the roof 603 where easy access to the ambient air is possible.

[0123] The first controllable valve 440 and the second controllable valve 441 are placed within the machine room 461 The pump 442 is placed within the machine room 442.

[0124] In this embodiment, as described above, the refrigerant of the second refrigeration circuit 410 is R515A and.

[0125] Structurally different, during use, the refrigeration system 400 operates in a manner similar to the refrigeration system 200 with the following key differences. and.

[0126] First, the receivers within the second refrigeration circuit 410 in the refrigeration system 400 become flooded evaporators i.e., evaporators 419, 430a, and 430b, that is, the refrigerant enters the evaporator as a liquid and a part of the liquid refrigerant does not completely evaporate into gas, which means that essentially no superheat occurs within the evaporator. How much refrigerant remains liquid depends on the operating conditions of the system 400. One feature of the refrigeration system 400 is the receiver 414. The receiver 414 is arranged to separate the gaseous and liquid refrigerants after they pass through the expansion valve 418, so that the refrigerant passing through to the medium-temperature cooling branch 417 and the low-temperature cooling branch 416 and thus through the evaporator 419 and the heat exchangers 430a, 430b is essentially 100% liquid. Another key feature of the refrigeration system 400 is the pump 442. The pump 442 is for the medium-temperature branch 417 and the low-temperature branch 4 and passes through - thus, it is possible for the refrigerant passing through to the evaporator 419 and the heat exchangers 430a, 430b - to pass through. The receiver 414 is arranged to separate them after the gaseous and liquid refrigerants pass through the expansion valve 418, so that the refrigerant passing through to the medium-temperature cooling branch 417 and the low-temperature cooling branch 416 and thus through the evaporator 419 and the heat exchangers 430a, 430b is essentially 100% liquid. Another key feature of the refrigeration system 400 is the pump 442. The pump 442 is for the medium-temperature branch 417 and the low-temperature branch 4 and passes through - thus, it is possible for the refrigerant passing through to the evaporator 419 and the heat exchangers 430a, 430b - to pass through. The refrigerant that can pass through to the evaporator 419 and the heat exchangers 430a, 430b is essentially 100% liquid. Another key feature of the refrigeration system 400 is the pump 442. The pump 442 is for the medium-temperature branch 417 and the low-temperature branch 4 and the key feature is the pump 442. The pump 442 is for the medium-temperature branch 417 and the low-temperature branch 4 Drive the refrigerant to the lunch 416. In an alternative system configuration, the concentration difference between the liquid phase and the gas phase of the refrigerant drives the system and does not require any pump or blower. The concentration difference drives the system and does not require any pump or blower.

[0127] Based on the disclosure and teachings contained herein, those skilled in the art will understand that there are several advantages associated with using a refrigeration configuration using a flooded evaporator in accordance with the present invention, such as that disclosed in system 400. Applicants have found that one such advantage is an unexpected improvement in the coefficient of performance (COP). Without necessarily being bound by any particular theory, this unexpected advantage is believed to result in part from the fact that the compressor 411 requires less work and the system enables an operation that involves less superheating of the refrigerant before it enters the compressor, thereby improving the cooling capacity of the second refrigeration circuit 410. Using a refrigeration configuration using a flooded evaporator in accordance with the present invention, such as that disclosed in system 400. There are several advantages associated with using a refrigeration configuration using a flooded evaporator in accordance with the present invention, such as that disclosed in system 400. One such advantage is an unexpected improvement in the coefficient of performance (COP). Without necessarily being bound by any particular theory, this unexpected advantage is believed to result in part from the fact that the compressor 411 requires less work and the system enables an operation that involves less superheating of the refrigerant before it enters the compressor, thereby improving the cooling capacity of the second refrigeration circuit 410. The compressor 411 requires less work and the system enables an operation that involves less superheating of the refrigerant before it enters the compressor, thereby improving the cooling capacity of the second refrigeration circuit 410. The compressor 411 requires less work and the system enables an operation that involves less superheating of the refrigerant before it enters the compressor, thereby improving the cooling capacity of the second refrigeration circuit 410. It is believed to result from the fact that the compressor 411 requires less work and the system enables an operation that involves less superheating of the refrigerant before it enters the compressor, thereby improving the cooling capacity of the second refrigeration circuit 410.

[0128] A second difference is that the refrigeration system 400 operates in a manner that provides a peripheral cooling branch 451 and controllable valves 440, 441, compared to the refrigeration system 200. The peripheral cooling branch 451 can bypass the compressor branch 450 to cool the refrigerant when the ambient temperature is low enough. The peripheral cooling branch 451 can bypass the compressor branch 450 to cool the refrigerant when the ambient temperature is low enough. This is achieved by routing the peripheral cooling branch 451 to the roof 460 to provide maximum exposure of the refrigerant to the ambient temperature. This is achieved by routing the peripheral cooling branch 451 to the roof 460 to provide maximum exposure of the refrigerant to the ambient temperature. This is sometimes referred to as winter operation. Advantageously, this provides that it essentially does not involve cooling the refrigerant in the second refrigeration circuit 410. Clearly, this is advantageous from a cost and environmental perspective as the energy consumption is significantly reduced compared to operating the compressor branch 450. Clearly, this is advantageous from a cost and environmental perspective as the energy consumption is significantly reduced compared to operating the compressor branch 450. This is advantageous from a cost and environmental perspective as the energy consumption is significantly reduced compared to operating the compressor branch 450.

[0129] For the purpose of cost, terms such as "flooded system" and "flooded cascade system" refer to the system of the present disclosure, in which at least one, preferably all, of the heat exchangers in the first refrigeration circuit (preferably a low-temperature circuit) for condensing the first refrigerant (preferably a low-temperature refrigerant) is a flooded evaporator for a second refrigerant (preferably a medium-temperature refrigerant). In a preferred embodiment, the medium-temperature evaporator is also a flooded evaporator. The potential advantages described for a cascade refrigeration system apply fully equally to a flooded cascade refrigeration system, and the terms used to describe a flooded refrigeration system and a non-flooded cascade refrigeration system are equivalent.

[0130] Further advantages of a flooded cascade refrigeration system include reduction of energy consumption by utilization of ambient cooling branches (winter operation), improvement of heat transfer performance by flooded operation of heat exchangers and evaporators, elimination of the need for a temperature control expansion valve by providing a pump in the circuit, and the ability to use low-cost materials for manufacturing it due to its suitability for the low-pressure refrigerant in the second refrigeration circuit.

[0131] In particular, from the perspective of the points described in this specification, the present invention includes a cascade refrigeration system, which includes a plurality of first refrigeration circuits, each first refrigeration circuit including a first refrigerant that is flammable and has a GWP of about 150 or less, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the first refrigerant condenses, a plurality of first refrigeration circuits, a second refrigeration circuit containing a non-flammable second refrigerant, and the above ​​​​​​​​​​​​​​A flooded evaporator in which a second refrigerant evaporates at a temperature lower than the above-described first refrigerant condensation temperature, and the above described second refrigerant evaporates in the above heat exchanger by absorbing heat from the above-described first refrigerant , comprising a flooded evaporator.

[0132] In particular, from the perspective of the points described in this specification, the present invention also includes a cascade refrigeration system , and this cascade refrigeration system includes a plurality of first refrigeration circuits, and each first refrigeration circuit includes a first refrigerant that is flammable and has a GWP of about 150 or less, and a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above-described first refrigerant condenses. A plurality of first refrigeration circuits, a second refrigeration circuit containing a non-flammable second refrigerant having a GWP of up to about 500 , and a flooded evaporator in which the above-described second refrigerant evaporates at a temperature lower than the above-described first refrigerant condensation temperature, and the above described second refrigerant evaporates in the above heat exchanger by absorbing heat from the above-described first refrigerant , comprising a flooded evaporator.

[0133] The present invention includes a cascade refrigeration system, and this cascade refrigeration system includes a plurality of low-temperature refrigeration circuits, and each first low-temperature refrigeration circuit is flammable and has a GWP of about 150 or less , a first refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above-described first refrigerant condenses in a temperature range of about -5°C to about -15°C. A plurality of low-temperature refrigeration circuits, a middle-temperature refrigeration circuit containing a non-flammable middle-temperature refrigerant, and a flooded evaporator in which the above-described middle-temperature refrigerant evaporates at a temperature lower than the above-described low-temperature refrigerant condensation temperature and in a range of about -5°C to about -15°C, and the above described middle-temperature refrigerant evaporates in the above heat exchanger by absorbing heat from the above-described low-temperature refrigerant , comprising a flooded evaporator.

[0134] The present invention includes a cascade refrigeration system, and this cascade refrigeration system includes a plurality of low-temperature refrigeration circuits. Each first low-temperature refrigeration circuit is combustible and has a GWP of about 150 or less, a first refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above-mentioned first refrigerant condenses in a temperature range of about -5°C to about -15°C. The system also includes a plurality of low-temperature refrigeration circuits, a medium-temperature refrigeration circuit containing a non-combustible medium-temperature refrigerant having a GWP of up to about 500, and a flooded evaporator in which the above-mentioned medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the above-mentioned low-temperature refrigerant and in a range of about -5°C to about -15°C, and the above-mentioned medium-temperature refrigerant absorbs heat from the above-mentioned low-temperature refrigerant and evaporates in the above-mentioned heat exchanger. The system further includes a flooded evaporator.

[0135] In a preferred embodiment, the present invention also includes a cascade refrigeration system. This cascade refrigeration system includes a plurality of low-temperature refrigeration circuits. Each low-temperature refrigeration circuit has a GWP of about 150 or less and contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the above-mentioned low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C. The system also includes a plurality of low-temperature refrigeration circuits, a medium-temperature refrigeration circuit containing a medium-temperature refrigerant, where the above-mentioned medium-temperature refrigerant is non-combustible, a medium-temperature refrigeration circuit, and a flooded evaporator in which the above-mentioned medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the above-mentioned low-temperature refrigerant and in a range of about -5°C to about -15°C. The above-mentioned medium-temperature refrigerant absorbs heat from the above-mentioned low-temperature refrigerant A flooded evaporator that evaporates in the heat exchanger by absorbing heat from .

[0136] In a preferred embodiment, the present invention also includes a cascade refrigeration system, and this cascade refrigeration system is a plurality of low-temperature refrigeration circuits, and each low-temperature refrigeration circuit has a GWP of about 150 or less and contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof a flammable low-temperature refrigerant, a compressor having a horsepower rating of about 2 hp or less, and a heat exchanger in which the above low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C, and includes a plurality of low-temperature refrigeration circuits, a medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the above medium-temperature refrigerant is non-flammable and has a GWP of at most about 500, a medium-temperature refrigeration circuit, and the above medium-temperature refrigerant evaporates in a flooded evaporator at a temperature below the above low-temperature refrigerant condensation temperature and in a range of about -5°C to about -15°C, wherein the above medium-temperature refrigerant evaporates in the above heat exchanger by absorbing heat from the above low-temperature refrigerant, and includes a flooded evaporator.

[0137] In a preferred embodiment, the present invention also includes a cascade refrigeration system, and this cascade refrigeration system is a plurality of low-temperature refrigeration circuits, and each low-temperature refrigeration circuit has a GWP of about 150 or less and contains at least about 50 wt%, or at least about 75 wt%, or at least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof A combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and the above-mentioned low-temperature cold A heat exchanger in which the medium condenses in a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration cycles A medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the medium-temperature refrigerant has a maximum GWP of about 500 And is non-flammable, containing at least about 50 wt%, or at least about 75 wt%, or at least At least 85 wt% of R1234ze(E), a medium-temperature refrigeration circuit, and the above The medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C A flooded evaporator, wherein the medium-temperature refrigerant absorbs heat from the low-temperature refrigerant and thereby Evaporates in the heat exchanger, and a flooded evaporator.

[0138] In a preferred embodiment, the present invention also includes a cascade refrigeration system, and this cascade A refrigeration system is a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit having a GWP of about 150 or less And containing at least about 50 wt%, or at least about 75 wt%, or at least At least 95 wt%, or at least 99 wt% of R744, R290, R600a, R1 270, R1234yf, R1234ze(E), R455A, and combinations thereof A combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and the above-mentioned low-temperature cold A heat exchanger in which the medium condenses in a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration cycles A medium-temperature refrigeration circuit containing a medium-temperature refrigerant, wherein the medium-temperature refrigerant has a maximum GWP of about 500 And containing at least about 50 wt%, or at least about 75 wt%, or at least At least 85 wt% of R1234ze(E) and about 10 wt% to about 15 wt% of R227e A non-flammable medium-temperature refrigeration circuit containing a, and the medium-temperature refrigerant evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. A flooded evaporator is provided. A flooded evaporator that evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. It is provided with a flooded evaporator.

[0139] In a preferred embodiment, the present invention also includes a cascade refrigeration system. This cascade refrigeration system is a plurality of low-temperature refrigeration circuits. Each low-temperature refrigeration circuit has a GWP of about 150 or less, and contains at least about 50% by weight, or at least about 75% by weight, or at least 95% by weight, or at least 99% by weight of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. It is provided with a combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the low-temperature refrigerant condenses in the temperature range of about -5°C to about -15°C. A plurality of low-temperature refrigeration circuits, and a medium-temperature refrigeration circuit containing a medium-temperature refrigerant. The medium-temperature refrigerant has a GWP of at most about 500 and contains about 88% by weight of R1234ze(E) and about 12% by weight of R227ea. It is a non-flammable medium-temperature refrigeration circuit. The medium-temperature refrigerant evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. A flooded evaporator is provided. It contains at least about 50% by weight, or at least about 75% by weight, or at least 95% by weight, or at least 99% by weight of R744, R290, R600a, R1270, R1234yf, R1234ze(E), R455A, and combinations thereof. A combustible low-temperature refrigerant, a compressor having a horsepower rating of about 2 horsepower or less, and a heat exchanger in which the low-temperature refrigerant condenses in the temperature range of about -5°C to about -15°C. And combinations thereof. A plurality of low-temperature refrigeration circuits, and a medium-temperature refrigeration circuit containing a medium-temperature refrigerant. The medium-temperature refrigerant has a GWP of at most about 500 and contains about 88% by weight of R1234ze(E) and about 12% by weight of R227ea. It is a non-flammable medium-temperature refrigeration circuit. The medium-temperature refrigerant evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. A flooded evaporator is provided. A plurality of low-temperature refrigeration circuits, and a medium-temperature refrigeration circuit containing a medium-temperature refrigerant. The medium-temperature refrigerant has a GWP of at most about 500 and contains about 88% by weight of R1234ze(E) and about 12% by weight of R227ea. It is a non-flammable medium-temperature refrigeration circuit. The medium-temperature refrigerant evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. A flooded evaporator is provided. A medium-temperature refrigeration circuit containing a medium-temperature refrigerant. The medium-temperature refrigerant has a GWP of at most about 500 and contains about 88% by weight of R1234ze(E) and about 12% by weight of R227ea. It is a non-flammable medium-temperature refrigeration circuit. The medium-temperature refrigerant evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. A flooded evaporator is provided. It has a GWP of at most about 500 and contains about 88% by weight of R1234ze(E) and about 12% by weight of R227ea. A non-flammable medium-temperature refrigeration circuit containing a, and the medium-temperature refrigerant evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. A flooded evaporator is provided. A flooded evaporator that evaporates in the temperature range below the condensation temperature of the low-temperature refrigerant and in the range of about -5°C to about -15°C. The medium-temperature refrigerant evaporates in the heat exchanger by absorbing heat from the low-temperature refrigerant. It is provided with a flooded evaporator.

[0140] Flooded cascade refrigeration system - alternative The above alternative for the cascade refrigeration system is a flooded cascade refrigeration system. fits well enough to the first and second refrigeration circuits, the circuit interface positions, and The term heat exchanger is equivalent. Other alternatives include the removal of the ambient cooling branch 451 and / or the conversion of the flooded system to a direct expansion system.

[0141] The ambient cooling branch 451 bypasses only the compressor 411 rather than the entire compressor branch so that the ambient cooling branch can be short and simplified, and still other variations of the system 400 are envisioned. This configuration is shown in FIG. 4A.

[0142] FIG. 4A shows a refrigeration system 400 that is mostly the same as the description regarding FIG. 4, except for the following. - The chiller 452 in FIG. 4 is not present because it is no longer needed. This is because the ambient cooling branch 451 no longer bypasses the chiller 413, so an ambient cooling branch dedicated chiller is not required. - The first controllable valve 440 is not present because it is no longer needed. This is because the refrigerant from the ambient cooling branch 451 is not brought into contact with the branch junction, but simply fed into the chiller 413 line. - The ambient cooling branch 451 is connected in parallel with the compressor 411 between the second controllable valve 441 and the line between the compressor 411 and the chiller 413.

[0143] Advantageously, by using a shortened ambient cooling branch, i.e., routing the branch from the receiver vessel outlet to the condenser inlet, first, the circuit is simplified because the chiller and the first controllable valve are no longer required at the inlet of the receiver pump, and second, the amount of extra piping for the ambient cooling branch and the number of components are reduced, thus Thus, a lower cost circuit is provided by reducing the material cost.

[0144] As will be apparent to those skilled in the art from the perspective of the teachings contained herein, the preferred module By the first refrigeration circuit design of the loop, the refrigeration system of the preferred embodiment of the present invention is a second In the refrigeration circuit, it enables the use of a non-flammable low-pressure refrigerant having a relatively low GWP. Furthermore , the system 400 enables the use of a flammable low-pressure refrigerant having a low GWP in the first refrigeration circuit . Furthermore, by the use of the ambient cooling branch, the system provides a reduced energy usage. Still further, by its flooded design, the system provides improved system efficiency. Thus, a refrigeration system with reduced environmental impact is provided through the use of reduced GWP refrigerants, reduced energy usage, and improved system efficiency .

[0145] Suction line heat exchanger An example of any further possible modification of the system forming part of this disclosure is that any number of built-in refrigeration circuits may include a suction line heat exchanger (SLHX).

[0146] More specifically, any of the first refrigeration circuits 220a, 220b, 220c within the system 200 may include an SLHX, and any of the first refrigeration circuits 420a, 420b may include an SLHX. For comparison, FIG. 7A shows a refrigeration circuit 700 without an SLHX, while FIG. 7B shows a refrigeration circuit 750 with an SLHX 760. The circuit 700 of FIG. 5A includes a compressor 710, a heat exchanger 720, an expansion valve 730, and an evaporator

[0147] ​It has a compressor 710, a heat exchanger 720, an expansion valve 730, and an evaporator 740. They are connected in series in the order listed. During use, the refrigeration circuit 700 functions as previously described as such.

[0148] The circuit 750 of FIG. 5B has the same components as the circuit 700, but an additional SLHX 760 is added. The SLHX provides a heat exchange interface between the line connecting the evaporator 740 and the compressor 710 and the line connecting the heat exchanger 720 and the expansion valve 730. In other words, the SLHX 760 is positioned between the line connecting the evaporator 740 and the compressor 710 (referred to as the vapor line in this specification) and the line following the heat exchanger 720 and the expansion valve 730 (referred to as the liquid line in this specification). During use, the SLHX transfers heat from the liquid line after the heat exchanger 720 to the vapor line after the evaporator 740. This has two effects, namely, first, an improvement in the efficiency of the circuit 70 0, and second, a reduction in the efficiency of the circuit 700. First, advantageously, on the liquid line side - i.e., the high-pressure side - subcooling of the liquid refrigerant increases. This is because the excess heat is discharged to the liquid expansion side, which reduces the temperature of the refrigerant entering the expansion valve 730. This additional subcooling leads to a lower inlet quality in the evaporator 740 after the expansion valve 730. This increases the enthalpy difference, thus improving the ability of the refrigerant to absorb heat in the evaporator 740 stage. Therefore, the performance of the evaporator 740 is improved.

[0149] During use, the SLHX transfers heat from the liquid line after the heat exchanger 720 to the vapor line after the evaporator 740. This has two effects, namely, first, an improvement in the efficiency of the circuit 70 0, and second, a reduction in the efficiency of the circuit 700. First, advantageously, on the liquid line side - i.e., the high-pressure side - subcooling of the liquid refrigerant increases. This is because the excess heat is discharged to the liquid expansion side, which reduces the temperature of the refrigerant entering the expansion valve 730. This additional subcooling leads to a lower inlet quality in the evaporator 740 after the expansion valve 730. This increases the enthalpy difference, thus improving the ability of the refrigerant to absorb heat in the evaporator 740 stage. Therefore, the performance of the evaporator 740 is improved.

[0150] First, advantageously, on the liquid line side - i.e., the high-pressure side - subcooling of the liquid refrigerant increases. This is because the excess heat is discharged to the liquid expansion side, which reduces the temperature of the refrigerant entering the expansion valve 730. This additional subcooling leads to a lower inlet quality in the evaporator 740 after the expansion valve 730. This increases the enthalpy difference, thus improving the ability of the refrigerant to absorb heat in the evaporator 740 stage. Therefore, the performance of the evaporator 740 is improved. Second, the efficiency of the circuit 700 is reduced. This is because the SLHX transfers heat from the liquid line to the vapor line, which reduces the temperature difference between the two lines. This reduces the driving force for heat transfer in the circuit 700, resulting in a decrease in the overall efficiency of the circuit 700. Second, the efficiency of the circuit 700 is reduced. This is because the SLHX transfers heat from the liquid line to the vapor line, which reduces the temperature difference between the two lines. This reduces the driving force for heat transfer in the circuit 700, resulting in a decrease in the overall efficiency of the circuit 700. Second, the efficiency of the circuit 700 is reduced. This is because the SLHX transfers heat from the liquid line to the vapor line, which reduces the temperature difference between the two lines. This reduces the driving force for heat transfer in the circuit 700, resulting in a decrease in the overall efficiency of the circuit 700. Second, the efficiency of the circuit 700 is reduced. This is because the SLHX transfers heat from the liquid line to the vapor line, which reduces the temperature difference between the two lines. This reduces the driving force for heat transfer in the circuit 700, resulting in a decrease in the overall efficiency of the circuit 700. Therefore, the performance of the evaporator 740 is improved.

[0151] Second, disadvantageously, on the vapor line side - i.e., the low pressure side - the refrigerant exiting the evaporator 740 receives excess heat from the liquid line, which effectively increases the superheat. This results in a higher suction line temperature. As a result of the higher suction line temperature to the compressor 710, the enthalpy difference of the compression process increases. This increases the power of the compressor required to compress the refrigerant. Therefore, this has a detrimental effect on the performance of the

[0152] system. In summary, to determine whether introducing the SLHX results in an overall beneficial effect, it is necessary to consider both the first and second effects of the improved evaporator capacity and the requirements for improved compressor power. For certain refrigerants such as R717, the use of the SLHX leads to an overall reduction in system efficiency. However, in contrast, the use of the SLHX leads to an overall beneficial effect for systems of the type illustrated in the drawings as systems 200 and 300 herein.

[0153] Supporting Data Here, data is presented that demonstrates the technical effects of the various configurations of the present disclosure and that is intended to assist those skilled in the art in practicing the various configurations.

[0154] Table 1 shows the overall GWP for the case of varying the ratio of R515A and R744 refrigerants in a refrigeration system, where 1 is the maximum combined value, i.e., 100%. According to the Intergovernmental Panel on Climate Change, R515A has a GWP of 403 and R7 55 has a GWP of 1. Therefore, the overall GWP for R515A with a ratio of 0 and R74 4 with a ratio of 1 is 1 [(1×1)=1]. Conversely, for R515 with a ratio of 0.05 The overall GWP of R755 with A and a ratio of 0.95 is 21.1 [(0.05 × 403) +(0.95×1)=21.1. Thus, Table 1 shows the results of the study considering the GWP standard. The charge ratio limitations are shown.

[0155] [Table 1]

[0156] Figure 6 shows the data from Table 1 in graphical form. The percentage of R515A is shown on the x-axis, and the percentage of total The specific GWP is shown on the y-axis. From this graph, the relative proportions of R515A and R744 and their GWPs can be seen. It is clear that there is a direct proportional relationship with P, and as the ratio of R515A increases , the GWP of the system increases. This is because R515A has a much higher GWP than R744. The direct proportional relationship is from a GWP of 1 for R515A with a ratio of 0 to a GWP of 1 for R515A with a ratio of 0. This is shown by the straight line on the graph that goes up to a GWP of about 400 for R515A. From the rough, the maximum allowed system GWP in the preferred embodiment is 150, It is clear that a ratio of about 0.35 is found for R515A.

[0157] Table 2 shows the results for R1233zd(E) refrigerant, R1233zd(E) with a ratio of 50% by weight, and A mixture of 50% by weight of R1234ze and 33% by weight of R1233zd(E) and and 67% by weight of R1234ze, and the boiling pressure at varying boiling temperatures. Indicates temperature.

[0158] [Table 2]

[0159] The test refrigeration system is operated by indoor refrigerant. R1233zd(E), tran sHCFO-1233zd, and R1234ze are transHFO-1234ze exist.

[0160] The results in Table 2 show that a composition in which the amount of transHFO-1234ze is at least 50% by weight enables the indoor circuit to operate under a pressure exceeding 1 atmosphere. Such a low-pressure system is advantageous as it avoids the need for a purge system - which aids in system complexity - while at the same time providing a sufficiently low system pressure to allow the use of relatively low-cost containers and conduits. Furthermore, the low pressure avoids refrigerant leaks that can occur in other high-pressure systems.

[0161] Another property that varies with the ratio of R1233zd(E) and R1234ze in the mixture is the flammability of the refrigerant in the event of a leak from the refrigeration system. Table 3 shows various weight compositions of mixtures of R1233zd(E ) and R1234ze, and the flammability of each composition. As is clear from Table 3, when measured according to ASTM 681, formulations having more than 67% by weight of transHFO-1234ze are flammable.

[0162]

Table 3

[0163] Table 4a shows formulations that are not previously described in this disclosure but are considered in Table 4b.

[0164]

Table 4a

[0165] Table 4b shows a comparison of the characteristics of different refrigerant combinations for a comparative refrigeration system without a mechanical subcooler (the " comparative example") described with respect to FIG. 1B, a comparative refrigeration system with a mechanical subcooler (the " "comparative example with a mechanical subcooler") described with respect to FIG. 1B, a cascade refrigeration system (the " "Option 1") described with respect to FIG. 2, and a flooded cascade refrigeration circuit (the " "Option 2") described with respect to FIG. 4.

[0166] **Table 4b**

[0167] Table 4b includes information regarding the coefficient of performance (COP) of each system. The COP is the ratio of the useful cooling output from the system to the work input to the system. A high COP means the same as a low operating cost. The relative COP is the COP with respect to the refrigeration system of the comparative example. to the comparative example refrigeration system. It is clear that the flooded cascade refrigeration circuit achieves the best COP since its value regarding COP is higher than that of the other systems in all cases. from Table 4b.

[0168] The results shown in Table 4b are based on the following assumptions. In the table, MT means medium temperature (the second refrigeration circuit), LT means low temperature (the first refrigeration circuit), and the units are as given.

[0169] ● The R404A of the comparative example combines the MT system and the LT system ● Load distribution ● ● ​​○LT: 1 / 3 (33,000 W) ○MT: 2 / 3 (67,000 W) ●Volumetric efficiency: 95% for both MT and LT ●Thermal insulation efficiency ○R404A: MT / LT, 0.72 / 0.68 ○R134a: MT, 0.687 ○R744: LT, 0.671 ●Condensing temperature: 105°F ●MT evaporation temperature: 20°F (for built-in units, 22°F due to less pressure drop) ) ●LT evaporation temperature: -25°F ●Evaporator superheat: 10°F ●Suction line temperature rise ○Comparative example: MT: 25°F, LT: 50°F ○Cascade / built-in type: MT: 10°F, LT: 25°F (built-in units have shorter lines and thus less heat intrusion) ○Cascade / pump type: MT: 10°F, LT: 25°F ●SLHX efficiency during use: 35% ●Mechanical subcooler outlet temperature: 50°F

[0170] It will be understood that the LT load in this example (33,000 watts) is provided in accordance with a preferred aspect of the present invention by the cumulative power ratings of a number of small compressors. For example, if the LT portion of a refrigeration system uses a compressor rated at approximately 1500 watts (about 2 horsepower), a number (e.g., 20) of such small compressors are used in accordance with the present invention. In contrast, it is contemplated that the compressor load carried by a medium-temperature system can be handled by a larger compressor in series (having a power rating of 5 horsepower or more) to provide cooling of 67,000 watts (about 90 horsepower).

[0171] ​​​​​Table 5 relates to different combinations of refrigerants within a cascade refrigeration system and to the second Referring to FIG. 1, a refrigeration system of a comparative example having an intake line liquid line (SLHX) in a refrigeration circuit (intermediate temperature stage) and a cascade refrigeration system described with reference to FIG. 2 are shown in comparison of characteristics. As in Table 4b, Table 5 includes information regarding the actual and relative COP of each system.

[0172] **Table 5**

[0173] It is clear from Table 5 that by using the SLHX, a higher COP is achieved compared to not using it. This is shown by the fact that for the same combination of refrigerants within the cascade refrigerant system, the values regarding COP are higher in Table 5 than in Table 4b. The present invention includes the following aspects. [1] A cascade refrigeration system, comprising: (a) a plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit comprising: (i) a flammable low-temperature refrigerant having a GWP of about 150 or less; (ii) a compressor having a horsepower rating of about 2 hp or less; (iii) a heat exchanger in which the flammable low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C; a plurality of low-temperature refrigeration circuits; (b) an intermediate-temperature refrigeration circuit containing a non-flammable intermediate-temperature refrigerant that evaporates at a temperature lower than the low-temperature refrigerant condensation temperature and in a range of about -5°C to about -15°C, the intermediate-temperature refrigerant evaporating in the heat exchanger by absorbing heat from the flammable refrigerant of the low-temperature refrigeration circuit; a cascade refrigeration system comprising. [2] The cascade refrigeration system according to [1], wherein each refrigeration circuit is within a modular refrigeration unit, and at least one of the modular refrigeration units is disposed in a first region that is generally open. [3] The cascade refrigeration system according to [2], wherein the second refrigeration circuit includes a portion that extends the second refrigeration circuit between the first region and the second region. [4] The cascade refrigeration system according to [3], wherein the second region is a machine room. [5] The cascade refrigeration system according to [4], wherein the second refrigeration circuit includes a portion that extends the second refrigeration circuit to a third region. [6] The cascade refrigeration system according to [1], wherein each first refrigeration circuit further comprises a fluid expansion device. [7] ​The cascade refrigeration system according to [6], wherein the fluid expansion device is a capillary tube. [8] The cascade refrigeration system according to [6], wherein the fluid expansion device is an orifice tube. [9] The cascade refrigeration system according to [1], wherein the non-flammable intermediate-temperature refrigerant is R515A.

[10] The cascade refrigeration system according to [1], wherein the flammable low-temperature refrigerant comprises at least about 50 wt% of R744, C3-C4 hydrocarbons, R1234yf, R1234ze(E), R455A, and combinations thereof.

[11] The cascade refrigeration system according to

[10] , wherein the flammable low-temperature refrigerant comprises at least about 50 wt% of R290, R600a, R1270, and combinations thereof.

[12] The cascade refrigeration system according to

[10] , wherein the flammable low-temperature refrigerant comprises at least about 75% by weight of R1234yf, R1234ze(E), R455A, and combinations thereof.

[13] The cascade refrigeration system according to [2], wherein the medium-temperature refrigeration system is disposed substantially entirely outside the low-temperature refrigeration unit, the flammable low-temperature refrigerant comprises at least about 75% by weight of R1234yf, R1234ze(E), R455A, and combinations thereof, and the non-flammable medium-temperature refrigerant is R515A.

[14] A cascade refrigeration system, (a) A plurality of low-temperature refrigeration circuits, each low-temperature refrigeration circuit comprising (i) A flammable low-temperature refrigerant having a GWP of about 150 or less, (ii) A compressor having a horsepower rating of about 2 horsepower or less, (iii) A heat exchanger in which the flammable low-temperature refrigerant condenses in a temperature range of about -5°C to about -15°C, and a plurality of low-temperature refrigeration circuits. (b) A medium-temperature refrigeration circuit comprising a non-flammable medium-temperature refrigerant that evaporates in the heat exchanger by absorbing heat from the flammable refrigerant in the low-temperature refrigeration circuit, wherein the heat exchanger is a flooded heat exchanger, and the non-flammable medium-temperature refrigerant evaporates at a temperature below the low-temperature refrigerant condensation temperature and in a range of about -5°C to about -15°C. A cascade refrigeration system comprising a medium-temperature refrigeration circuit.

[15] The cascade refrigeration system according to

[14] , wherein each refrigeration circuit is within a modular refrigeration unit, and at least one of the modular refrigeration units is disposed in a generally open first region.

[16] The cascade refrigeration system according to

[15] , wherein each first refrigeration circuit further comprises a fluid expansion device.

[17] The cascade refrigeration system according to

[16] , wherein the fluid expansion device is a capillary tube.

[18] The cascade refrigeration system according to

[17] , wherein the fluid expansion device is an orifice tube.

[19] The cascade refrigeration system according to

[14] , wherein the non-flammable medium-temperature refrigerant is R515A, and the flammable low-temperature refrigerant comprises at least about 50% by weight of R744, C3 - C4 hydrocarbons, R1234yf, R1234ze(E), R455A, and combinations thereof.

[20] The medium-temperature refrigeration system is disposed substantially entirely outside the low-temperature refrigeration unit, and the flammable low-temperature refrigerant comprises at least about 75% by weight of R1234yf, R1234ze(E), R455A, and combinations thereof, and the cascade refrigeration system described in

[15]

Claims

**Claim 1** A method of providing cooling in a commercial cascade refrigeration system, comprising: (a) circulating a flammable low-temperature refrigerant in a plurality of built-in low-temperature refrigeration circuits, wherein: (i) the flammable low-temperature refrigerant has a GWP of about 150 or less; (ii) each of the built-in low-temperature refrigeration circuits has a compressor with a horsepower rating of about 2 horsepower or less; (iii) each of the built-in low-temperature refrigeration circuits has a heat exchanger in which the flammable low-temperature refrigerant condenses; and (b) circulating a non-flammable medium-temperature refrigerant in a medium-temperature refrigeration circuit in which the non-flammable medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the flammable low-temperature refrigerant, wherein the non-flammable medium-temperature refrigerant absorbs heat from the flammable low-temperature refrigerant of the low-temperature refrigeration circuit and evaporates in the heat exchanger; wherein the non-flammable medium-temperature refrigerant comprises a refrigerant comprising at least 75 wt% R1234ze(E) and 10 wt% - 15 wt% R227ea. **Claim 2** The method of claim 1, wherein each refrigeration circuit is within a modular refrigeration unit, and at least one of the modular refrigeration units is disposed in a generally unenclosed first area. **Claim 3** The method of claim 2, wherein the medium-temperature refrigeration circuit includes a portion that extends the medium-temperature refrigeration circuit between the first area and a second area. **Claim 4** The method of claim 3, wherein the second area is a machine room. **Claim 5** The method of claim 4, wherein the medium-temperature refrigeration circuit includes a portion that extends the medium-temperature refrigeration circuit to a third area. **Claim 6** The method of claim 1, wherein each low-temperature refrigeration circuit further comprises a fluid expansion device. **Claim 7** The method of claim 6, wherein the fluid expansion device is a capillary tube. **Claim 8** The method of claim 6, wherein the fluid expansion device is an orifice tube. **Claim 9** The method of claim 1, wherein the non-flammable medium-temperature refrigerant comprises at least 85 wt% R1234ze(E) and 10 wt% - 15 wt% R227ea. **Claim 10** The method of claim 1, wherein the non-flammable medium-temperature refrigerant is R515A. **Claim 11** The method of claim 1, wherein the flammable low-temperature refrigerant comprises at least about 50 wt% R744, C3 - C4 hydrocarbons, R1234yf, R1234ze(E), R455A, and combinations thereof. **Claim 12** The method of claim 11, wherein the flammable cryogenic refrigerant comprises at least about 50 wt% of R290, R600a, R1270, and combinations thereof.

13. The method of claim 11, wherein the flammable cryogenic refrigerant comprises at least about 75 wt% of R1234yf, R1234ze(E), R455A, and combinations thereof.

14. The method of claim 2, wherein the medium-temperature refrigeration system is disposed substantially entirely outside the cryogenic refrigeration unit, the flammable cryogenic refrigerant comprises at least about 75 wt% of R1234yf, R1234ze(E), R455A, and combinations thereof, and the non-flammable medium-temperature refrigerant is R515A.

15. A method of providing cooling in a commercial cascade refrigeration system, comprising: (a) circulating a flammable cryogenic refrigerant in a plurality of built-in cryogenic refrigeration circuits, wherein: (i) the flammable cryogenic refrigerant has a GWP of about 150 or less; (ii) each of the built-in cryogenic refrigeration circuits has a compressor with a horsepower rating of about 2 horsepower or less; and (iii) each of the built-in cryogenic refrigeration circuits has a heat exchanger in which the flammable cryogenic refrigerant condenses; and (b) circulating a non-flammable medium-temperature refrigerant in a medium-temperature refrigeration circuit that evaporates in the heat exchanger by the non-flammable medium-temperature refrigerant absorbing heat from the flammable cryogenic refrigerant within the cryogenic refrigeration circuit, wherein the heat exchanger is a flooded heat exchanger and the non-flammable medium-temperature refrigerant evaporates at a temperature below the condensation temperature of the flammable cryogenic refrigerant, and the non-flammable medium-temperature refrigerant comprises a refrigerant comprising at least 75 wt% of R1234ze(E) and 10 wt% to 15 wt% of R227ea.

16. The method of claim 15, wherein each cryogenic refrigeration circuit further comprises a fluid expansion device.

17. The method of claim 16, wherein the fluid expansion device is a capillary tube.

18. The method of claim 16, wherein the fluid expansion device is an orifice tube.

19. The method of claim 15, wherein the non-flammable medium-temperature refrigerant is R515A, and the flammable cryogenic refrigerant comprises at least about 50 wt% of R744, C3-C4 hydrocarbons, R1234yf, R1234ze(E), R455A, and combinations thereof. **Claim 20**: The method according to claim 15, wherein the non-flammable medium-temperature refrigerant comprises at least 85% by weight of R1234ze(E) and 10% to 15% by weight of R227ea. **Claim 21** Each refrigeration circuit is within a modular refrigeration unit, and at least one of the modular refrigeration units is disposed within a first region that is generally open. The medium-temperature refrigeration system is disposed substantially entirely outside of the low-temperature refrigeration unit, and the flammable low-temperature refrigerant comprises at least about 75% by weight of R1234yf, R1234ze(E), R455A, and combinations thereof. The method according to claim 15, wherein the non-flammable medium-temperature refrigerant is R515A.

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