Waste heat recovery type cascade refrigeration method

Abstract

The invention relates to the technical field of refrigeration, in particular to a waste heat recovery type cascade refrigeration method which is achieved through a cascade refrigeration system which comprises a first refrigeration module and a second refrigeration module. The first refrigeration module comprises a first compressor, a first heat exchanger, a second heat exchanger, an evaporator and a first pressure reduction part; the second refrigeration module comprises a second compressor, a condenser, a third heat exchanger and a second pressure reduction part. According to the invention, the refrigerant finally flowing to the evaporator is fully supercooled, and the refrigerant is prevented from generating flash gas during subsequent pressure reduction and temperature reduction, so that the evaporation heat exchange effect and the refrigeration efficiency are ensured. In addition, the utilization degree of the refrigerant in the refrigerating system is improved, so that the energy consumption of the refrigerating system is reduced, and the operation cost of the refrigerating system is reduced.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a waste heat recovery cascade refrigeration method. Background Art

[0002] In the environmental test chamber field, cascade refrigeration systems are a common cooling method due to their ability to achieve lower temperatures. This system uses two compressors charged with refrigerants of different boiling points to achieve cooling, meeting the test chamber's wide temperature control requirements. At present, in the cooling method of some cascade refrigeration systems, the refrigerant is only cooled once through the condenser or heat exchanger, which may not be fully supercooled. This will cause the refrigerant to produce flash gas when it is pressurized and cooled at the throttling element. This gas cannot participate in the effective heat absorption of the evaporator, but will occupy the evaporation space, thereby affecting the evaporation heat exchange effect and ultimately reducing the refrigeration efficiency.

[0003] Therefore, how to solve the above-mentioned deficiencies in the prior art has become the subject to be studied and solved by the present invention. Summary of the Invention

[0004] The object of the present invention is to provide a waste heat recovery cascade refrigeration method.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A waste heat recovery cascade refrigeration method is implemented by a cascade refrigeration system, wherein the cascade refrigeration system includes a first refrigeration module and a second refrigeration module; the first refrigeration module includes a first compressor, a first heat exchanger, a second heat exchanger, an evaporator, and a first pressure reducing element; the second refrigeration module includes a second compressor, a condenser, a third heat exchanger, and a second pressure reducing element; Waste heat recovery cascade refrigeration methods include: The second refrigeration module is started, and the second compressor delivers high-temperature and high-pressure refrigeration steam to the condenser; The high-temperature and high-pressure refrigeration steam is converted into medium-temperature and high-pressure refrigerant through the condenser and transported to the third heat exchanger; The third heat exchanger delivers medium-temperature and high-pressure refrigerant to the second pressure-reducing element; The medium-temperature and high-pressure refrigerant is converted into a low-temperature and low-pressure liquid refrigerant through the second pressure reducing element; Part of the low-temperature, low-pressure liquid refrigerant output by the second pressure reducing element is sent to the third heat exchanger and converted into gaseous refrigerant by heat exchange with the medium-temperature, high-pressure refrigerant output by the condenser, and the remaining low-temperature, low-pressure liquid refrigerant is sent to the first heat exchanger and converted into gaseous refrigerant through heat exchange treatment; delivering the gaseous refrigerant in the second refrigeration module to the feed end of the second compressor; The first refrigeration module is started, and the first compressor delivers high-temperature and high-pressure refrigeration steam to the first heat exchanger, which is heat-exchanged into medium-temperature and high-pressure refrigerant and then delivered to the second heat exchanger; The second heat exchanger delivers medium-temperature and high-pressure refrigerant to the first pressure-reducing component; The medium-temperature and high-pressure refrigerant is converted into a low-temperature and low-pressure liquid refrigerant through a first pressure reducing element; Part of the low-temperature, low-pressure liquid refrigerant output by the first pressure-reducing element is sent to the second heat exchanger and converted into gaseous refrigerant by heat exchange with the medium-temperature, high-pressure refrigerant output by the first heat exchanger; and the remaining low-temperature, low-pressure liquid refrigerant is sent to the evaporator and converted into gaseous refrigerant through heat exchange treatment; The gaseous refrigerant in the first refrigeration module is delivered to the feed end of the first compressor.

[0006] In the above solution, the first refrigeration module can cool the internal structure of the environmental test chamber, and the second refrigeration module exchanges heat with the first refrigeration module.

[0007] The heat exchanger itself is an existing setting, and the specific settings of its discharge end and feed end are not described in detail here, and there is no restriction on the type of heat exchanger.

[0008] The first compressor is of the same type as the second compressor, but is charged with a refrigerant having a different boiling point to meet a larger cooling load.

[0009] It should be noted that the above-mentioned descriptions of high temperature and high pressure only indicate the differences between refrigerants in different stages. Taking temperature as an example, high temperature, medium temperature and low temperature are mentioned above. The specific temperature range is not the innovation of this application. If you need to know more, you can refer to the existing technology. For example, for the specific temperature numerical range of high-temperature and high-pressure refrigeration steam, you can refer to the existing cascade refrigeration system.

[0010] The first refrigeration module is used for the following description. The second refrigeration module can refer to this description: First, a portion of the refrigerant output from the first heat exchanger exchanges heat with another portion of the refrigerant output from the first heat exchanger through the second heat exchanger, thereby ensuring that the refrigerant that ultimately flows to the evaporator is sufficiently supercooled. This prevents this portion of refrigerant from generating flash gas during subsequent pressure and temperature reduction, thereby ensuring evaporative heat exchange and cooling efficiency. Second, by utilizing part of the refrigerant outputted from the first heat exchanger to exchange heat with another part of the refrigerant outputted from the first heat exchanger, the utilization rate of the refrigerant in the refrigeration system is increased to reduce the energy consumption of the refrigeration system and thus reduce the operating cost of the refrigeration system.

[0011] According to a further technical solution, the first feed end of the first heat exchanger is connected to the discharge end of the first compressor via a first pipeline; The first feed end of the second heat exchanger is connected to the first discharge end of the first heat exchanger through a second pipeline; The evaporator is connected to the first discharge end of the second heat exchanger through a third pipe, and is connected to the feed end of the first compressor through a fourth pipe; The third pipeline is connected to the second feed end of the second heat exchanger through a fifth pipeline; The second discharge end of the second heat exchanger is connected to the feed end of the first compressor through a sixth pipeline; The first pressure reducing member is at least provided on the third pipeline; The feed end of the condenser is connected to the discharge end of the second compressor through a first flow channel; The first feed end of the third heat exchanger is connected to the discharge end of the condenser through a second flow channel; The first discharge end of the third heat exchanger is connected to the second feed end of the first heat exchanger through a third flow channel; The second discharge end of the first heat exchanger is connected to the feed end of the second compressor through a fourth flow channel; The third flow channel is connected to the second feed end of the third heat exchanger through a fifth flow channel; The second discharge end of the third heat exchanger is connected to the feed end of the second compressor through a sixth flow channel; The second pressure reducing component is at least provided in the third flow channel.

[0012] The working process of the refrigeration system is as follows: The second refrigeration module is started first, and the high-temperature and high-pressure refrigeration steam discharged from the second compressor enters the condenser for cooling, and then enters the third heat exchanger; The third heat exchanger discharges medium-temperature, high-pressure refrigerant, which is then converted into low-temperature, low-pressure liquid refrigerant by the second pressure-reducing element. Part of the liquid refrigerant flows back into the third heat exchanger through the fifth flow channel, where it exchanges heat with the medium-temperature, high-pressure refrigerant output from the condenser and is converted into gaseous refrigerant, which then flows back to the feed end of the second compressor. Another part of the low-temperature and low-pressure liquid refrigerant enters the second feed end of the first heat exchanger along the main path (the third flow channel). This part of the liquid refrigerant is also converted into gaseous refrigerant through heat exchange, and then flows back to the feed end of the second compressor, thus repeating the cycle. After starting the second refrigeration module, the first refrigeration module is started. The high-temperature and high-pressure refrigeration steam discharged from the first compressor enters the first heat exchanger and exchanges heat with the low-temperature and low-pressure liquid refrigerant discharged from the second refrigeration module into the first heat exchanger, and then enters the second heat exchanger. The second heat exchanger discharges medium-temperature, high-pressure refrigerant, which is then converted into low-temperature, low-pressure liquid refrigerant by the first pressure-reducing element. Part of the liquid refrigerant flows back into the second heat exchanger through the fifth pipe, and is converted into gaseous refrigerant by exchanging heat with the medium-temperature, high-pressure refrigerant output from the first heat exchanger, and then flows back to the feed end of the first compressor. Another part of the low-temperature and low-pressure liquid refrigerant enters the evaporator along the main route (the third pipeline). This part of the liquid refrigerant is also converted into gaseous refrigerant, and then flows back to the feed end of the first compressor, thus circulating.

[0013] In the above structure, the first refrigeration module is continued to be described. The fifth pipe and the sixth pipe can form a bypass branch to balance the pressure at the inlet end of the first compressor, avoiding the need to set up a separate bypass branch and reducing structural costs.

[0014] According to a further technical solution, the first pressure reducing member includes: a first thermal expansion valve, provided on the third pipeline; a second thermal expansion valve, provided on the fifth pipeline; The second pressure reducing member comprises: a third thermal expansion valve, disposed in the third flow passage; The fourth thermal expansion valve is provided in the fifth flow passage.

[0015] Take the first pressure reducing component as an example: On the one hand, thermal expansion valves are installed on both the third and fifth pipes to independently control the flow rates of the third and fifth pipes; On the other hand, the connection point between the third pipe and the fifth pipe is not subject to significant restrictions, and the line layout in the refrigeration system can be flexibly performed.

[0016] If there is no second thermal expansion valve, the connection point between the third pipeline and the fifth pipeline is greatly restricted, and the fluid must first pass through the first thermal expansion valve before entering this connection point.

[0017] In a further technical solution, the first refrigeration module further includes: a first control valve, provided on the third pipeline; a second control valve, provided on the fifth pipeline; The second refrigeration module further includes: a third control valve, disposed in the third flow channel; The fourth control valve is provided in the fifth flow channel.

[0018] Taking the first control valve as an example, the second control valve, the third control valve and the fourth control valve refer to this description: the first control valve is used in conjunction with the first pressure reducing component. When the refrigeration system stops running, the first control valve can quickly cut off the flow of refrigerant before the first pressure reducing component takes effect, so as to protect the evaporator and other equipment and achieve long-term stable operation of the refrigeration system.

[0019] In a further technical solution, the first refrigeration module further includes: a seventh pipeline, having two ends connected to the first pipeline and the feed end of the first compressor respectively; a fifth control valve, comprising at least one control sub-valve provided on the seventh pipeline; The second refrigeration module further includes: a seventh flow channel, two ends of which are respectively connected to the first flow channel and the feed end of the second compressor; The sixth control valve includes at least one control sub-valve arranged on the seventh flow channel.

[0020] The seventh pipe and the fifth control valve are used for explanation. The seventh flow channel and the sixth control valve can refer to this explanation: First, the seventh pipeline can be directly connected to the feed end of the first compressor, or can be indirectly connected to the feed end of the first compressor (e.g., through the fourth pipeline), and this embodiment does not impose any restrictions; Second, the fifth control valve may include two control sub-valves, one of which is a solenoid valve and the other is a bypass valve. The solenoid valve can quickly cut off or connect the seventh pipeline to avoid pressure fluctuations or other problems caused by the slow response speed of the bypass valve; Third, the seventh pipeline constitutes a bypass branch, which is initially in a closed state. When the pressure at the feed end of the first compressor is too low, this bypass branch is opened. This bypass branch can directly lead a portion of the high-temperature and high-pressure refrigeration vapor discharged from the discharge end of the first compressor back to the feed end of the first compressor to balance the pressure at the feed end of the first compressor.

[0021] According to a further technical solution, the sixth pipeline is connected to the feed end of the first compressor through the fourth pipeline; The seventh pipeline is connected to the feed end of the first compressor through the fourth pipeline or the sixth pipeline; The sixth flow channel is connected to the feed end of the second compressor through the fourth flow channel; The seventh flow channel is connected to the feed end of the second compressor through the fourth flow channel or the sixth flow channel.

[0022] Taking the example of the sixth pipeline being connected to the feed end of the first compressor through the fourth pipeline, similar descriptions in this embodiment refer to this description: the sixth pipeline is not directly connected to the feed end of the first compressor. On the one hand, the length of the sixth pipeline can be shortened to reduce the structural cost; on the other hand, it can avoid the disorderly layout of multiple pipelines at the feed end of the first compressor, which affects the difficulty of subsequent maintenance.

[0023] According to a further technical solution, the fifth control valve and the sixth control valve each include two control sub-valves connected in series.

[0024] For the description of the control sub-valves, please refer to the above embodiment. This embodiment further clarifies the specific settings of the fifth control valve and the sixth control valve.

[0025] In a further technical solution, the first refrigeration module further includes: an eighth pipeline, having two ends connected to the fifth pipeline and the sixth pipeline respectively; a seventh control valve, provided on the eighth pipeline; The second refrigeration module further includes: an eighth flow channel, having two ends connected to the fifth flow channel and the sixth flow channel respectively; The eighth control valve is provided in the eighth flow channel.

[0026] For the description of the seventh control valve and the eighth control valve, please refer to the description of similar control valves in the above embodiment. Taking the seventh control valve as an example, the seventh control valve is mainly provided to control the flow of the eighth pipeline.

[0027] Taking the eighth pipe as an example, the eighth flow channel refers to this description: the eighth pipe is actually a bypass branch. The eighth pipe is initially in a closed state. When the pressure at the feed end of the first compressor is too high, the eighth pipe opens, and part of the liquid refrigerant entering the fifth pipe flows directly through the eighth pipe to the feed end of the first compressor to balance the pressure at the feed end of the first compressor; The temperature at the feed end of the first compressor may also be too high. At this time, low-temperature and low-pressure liquid refrigerant can be transported to the feed end of the first compressor through the sixth pipeline to cool it down, thereby protecting the first compressor from damage and replacing the method of constantly starting and stopping the first compressor to achieve the cooling effect, thereby saving energy consumption.

[0028] Before the eighth pipeline is installed, the sixth pipeline only transports the gaseous refrigerant output by the second heat exchanger; after the eighth pipeline is installed, the liquid refrigerant and the gaseous refrigerant merge in the sixth pipeline and are transported to the feed end of the first compressor.

[0029] In a further technical solution, the first refrigeration module further includes: Storage containers; a ninth pipeline, having two ends connected to the first pipeline and the feed end of the storage container respectively; a ninth control valve, provided on the ninth pipeline; a tenth pipeline, two ends of which are respectively connected to the discharge end of the storage container and the feed end of the first compressor; The tenth control valve is provided on the tenth pipeline.

[0030] When the pressure in the main circuit of the first refrigeration module is higher than the set pressure, the refrigerant can flow into the storage container to protect the safety of the refrigeration system; when the pressure is lower than the set pressure, the refrigerant can flow from the storage container to the first compressor.

[0031] The terms “first”, “second”, etc. used in this document do not specifically refer to an order or sequence, nor are they used to limit this case. They are only used to distinguish components or operations described with the same technical terms.

[0032] As used herein, “connected” or “positioned” may refer to two or more components or devices being in direct or indirect physical contact with each other, or may refer to two or more components or devices operating or moving with each other.

[0033] The terms “include”, “including”, “have”, etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] Unless otherwise noted, the terms used herein generally have their ordinary meanings in the art, in the context of this application, and in the specific context. Certain terms used to describe this application are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of this application.

[0035] The terms "front", "back", "up", "down", "left", "right", etc. used in this article are all directional terms. In this case, they are only used to illustrate the positional relationship between the various structures, and are not used to limit the protection plan of this case and the specific direction during actual implementation.

[0036] The advantages of the present invention are as follows: The first refrigeration module is used for the following description. The second refrigeration module can refer to this description: First, a portion of the refrigerant output from the first heat exchanger exchanges heat with another portion of the refrigerant output from the first heat exchanger through the second heat exchanger, thereby ensuring that the refrigerant that ultimately flows to the evaporator is sufficiently supercooled. This prevents this portion of refrigerant from generating flash gas during subsequent pressure and temperature reduction, thereby ensuring evaporative heat exchange and cooling efficiency. Second, by utilizing part of the refrigerant outputted from the first heat exchanger to exchange heat with another part of the refrigerant outputted from the first heat exchanger, the utilization rate of the refrigerant in the refrigeration system is increased to reduce the energy consumption of the refrigeration system and thus reduce the operating cost of the refrigeration system.

[0037] In summary, the present application improves the utilization rate of the refrigerant in the refrigeration system, thereby achieving sufficient supercooling of the refrigerant that ultimately flows to the evaporator and reducing the operating cost of the refrigeration system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of a cascade refrigeration system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the refrigeration process of the second refrigeration module according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the refrigeration process of the first refrigeration module according to an embodiment of the present invention.

[0039] In the above figures: 1, first refrigeration module; 11, first compressor; 12, first heat exchanger; 13, first pipeline; 14, second heat exchanger; 15, second pipeline; 16, evaporator; 17, third pipeline; 18, fourth pipeline; 19, fifth pipeline; 101, sixth pipeline; 102, first pressure reducing member; 1021, first thermal expansion valve; 1022, second thermal expansion valve; 103, first control valve; 104, second control valve; 105, seventh pipeline; 106, fifth control valve; 107, eighth pipeline; 108, seventh control valve; 109, storage container; 1001, ninth pipeline 1002, ninth control valve; 1003, tenth pipeline; 1004, tenth control valve; 2, second refrigeration module; 21, second compressor; 22, condenser; 23, first flow channel; 24, third heat exchanger; 25, second flow channel; 26, third flow channel; 27, fourth flow channel; 28, fifth flow channel; 29, sixth flow channel; 201, second pressure reducing component; 2011, third thermal expansion valve; 2012, fourth thermal expansion valve; 202, third control valve; 203, fourth control valve; 204, seventh flow channel; 205, sixth control valve; 206, eighth flow channel; 207, eighth control valve. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments: Embodiment: The present invention will be clearly illustrated below with drawings and detailed descriptions. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the techniques taught by the present invention without departing from the spirit and scope of the present invention.

[0041] The terms used herein are for describing specific embodiments only and are not intended to be limiting of the present invention. Singular forms such as "a," "the," "this," "this," and "the" as used herein also include plural forms.

[0042] See also Figure 1-Figure 3 A waste heat recovery cascade refrigeration method includes a cascade refrigeration system, wherein the cascade refrigeration system includes a first refrigeration module 1 and a second refrigeration module 2; the first refrigeration module 1 includes a first compressor 11, a first heat exchanger 12, a second heat exchanger 14, an evaporator 16, and a first pressure reducing component 102; the second refrigeration module 2 includes a second compressor 21, a condenser 22, a third heat exchanger 24, and a second pressure reducing component 201; Waste heat recovery cascade refrigeration methods include: The second refrigeration module 2 is started, and the second compressor 21 delivers (first) high-temperature and high-pressure refrigeration steam to the condenser 22; The (first) high-temperature and high-pressure refrigeration steam is converted into a (first) medium-temperature and high-pressure refrigerant through the condenser 22 and transported to the third heat exchanger 24; The third heat exchanger 24 delivers the (first) medium-temperature and high-pressure refrigerant to the second pressure reducing element 201 ; The (first) medium-temperature and high-pressure refrigerant is converted into a (first) low-temperature and low-pressure liquid refrigerant by the second pressure reducing element 201; Part of the (first) low-temperature, low-pressure liquid refrigerant output by the second pressure reducing element 201 is sent to the third heat exchanger 24 and converted into the (first) gaseous refrigerant by exchanging heat with the (first) medium-temperature, high-pressure refrigerant output by the condenser 22, and the remaining (first) low-temperature, low-pressure liquid refrigerant is sent to the first heat exchanger 12 and converted into the (first) gaseous refrigerant by heat exchange treatment; delivering the (first) gaseous refrigerant in the second refrigeration module 2 to the feed end of the second compressor 21; The first refrigeration module 1 is started, and the first compressor 11 delivers the (second) high-temperature and high-pressure refrigeration steam to the first heat exchanger 12, which is heat-exchanged to become the (second) medium-temperature and high-pressure refrigerant and then delivered to the second heat exchanger 14; The second heat exchanger 14 delivers the (second) medium-temperature and high-pressure refrigerant to the first pressure reducing element 102 ; The (second) medium-temperature and high-pressure refrigerant is converted into a (second) low-temperature and low-pressure liquid refrigerant by the first pressure reducing element 102 ; Part of the (second) low-temperature, low-pressure liquid refrigerant output by the first pressure-reducing element 102 is fed into the second heat exchanger 14 and converted into the (second) gaseous refrigerant by exchanging heat with the (second) medium-temperature, high-pressure refrigerant output by the first heat exchanger 12; and the remaining (second) low-temperature, low-pressure liquid refrigerant is fed to the evaporator 16 and converted into the (second) gaseous refrigerant by heat exchange. The (second) gaseous refrigerant in the first refrigeration module 1 is delivered to the feed end of the first compressor 11 .

[0043] Here, high-temperature, high-pressure refrigeration steam is used as an example. It should not be assumed that the high-temperature, high-pressure refrigeration steam in the second refrigeration module 2 is necessarily the same as the high-temperature, high-pressure refrigeration steam in the first refrigeration module 1. The two may differ in temperature and pressure. Here, the high-temperature, high-pressure refrigeration steam in the second refrigeration module 2 is set as the first high-temperature, high-pressure refrigeration steam, and the high-temperature, high-pressure refrigeration steam in the first refrigeration module 1 is set as the second high-temperature, high-pressure refrigeration steam for differentiation. For details, please refer to the description in brackets in this embodiment.

[0044] The first refrigeration module 1 can cool the internal structure of the environmental test chamber, and the second refrigeration module 2 exchanges heat with the first refrigeration module 1.

[0045] The heat exchanger itself is an existing setting, and the specific settings of its discharge end and feed end are not described in detail here, and there is no restriction on the type of heat exchanger.

[0046] The first compressor 11 and the second compressor 21 are of the same type, but are charged with refrigerants having different boiling points to meet a larger cooling load.

[0047] It should be noted that the above-mentioned descriptions of high temperature and high pressure only indicate the differences between refrigerants in different stages. Taking temperature as an example, high temperature, medium temperature and low temperature are mentioned above. The specific temperature range is not the innovation of this application. If you need to know more, you can refer to the existing technology. For example, for the specific temperature numerical range of high-temperature and high-pressure refrigeration steam, you can refer to the existing cascade refrigeration system.

[0048] The first refrigeration module 1 is used for illustration, and the second refrigeration module 2 refers to this illustration: First, a portion of the refrigerant output from the first heat exchanger 12 exchanges heat with another portion of the refrigerant output from the first heat exchanger 12 through the second heat exchanger 14, thereby ensuring that the refrigerant ultimately flowing to the evaporator 16 is sufficiently supercooled, thereby preventing this portion of the refrigerant from generating flash gas during subsequent pressure and temperature reduction, thereby ensuring evaporative heat exchange and refrigeration efficiency. Second, part of the refrigerant outputted from the first heat exchanger 12 is used to exchange heat with another part of the refrigerant outputted from the first heat exchanger 12, thereby improving the utilization rate of the refrigerant in the refrigeration system to reduce the energy consumption of the refrigeration system and reduce the operating cost of the refrigeration system.

[0049] In this embodiment, the first feed end of the first heat exchanger 12 is connected to the discharge end of the first compressor 11 through a first pipe 13; The first feed end of the second heat exchanger 14 is connected to the first discharge end of the first heat exchanger 12 through a second pipe 15; The evaporator 16 is connected to the first discharge end of the second heat exchanger 14 through a third pipe 17 and is connected to the feed end of the first compressor 11 through a fourth pipe 18; The third pipeline 17 is connected to the second feed end of the second heat exchanger 14 through the fifth pipeline 19; The second discharge end of the second heat exchanger 14 is connected to the feed end of the first compressor 11 through a sixth pipeline 101; The first pressure reducing member 102 is at least provided on the third pipe 17; The feed end of the condenser 22 is connected to the discharge end of the second compressor 21 through the first flow channel 23; The first feed end of the third heat exchanger 24 is connected to the discharge end of the condenser 22 through a second flow channel 25; The first discharge end of the third heat exchanger 24 is connected to the second feed end of the first heat exchanger 12 through a third flow channel 26; The second discharge end of the first heat exchanger 12 is connected to the feed end of the second compressor 21 through a fourth flow channel 27; The third flow channel 26 is connected to the second feed end of the third heat exchanger 24 through the fifth flow channel 28; The second discharge end of the third heat exchanger 24 is connected to the feed end of the second compressor 21 through a sixth flow channel 29; The second pressure reducing member 201 is at least disposed in the third flow channel 26 .

[0050] The working process of the refrigeration system is as follows: First, the second refrigeration module 2 is started, and the high-temperature and high-pressure refrigeration steam discharged from the second compressor 21 enters the condenser 22 for cooling, and then enters the third heat exchanger 24; The third heat exchanger 24 discharges the medium-temperature, high-pressure refrigerant, which is then converted into a low-temperature, low-pressure liquid refrigerant by the second pressure-reducing element 201. Part of the liquid refrigerant flows back into the third heat exchanger 24 through the fifth flow channel 28, and is converted into a gaseous refrigerant by exchanging heat with the medium-temperature, high-pressure refrigerant output from the condenser 22. The gaseous refrigerant then flows back to the feed end of the second compressor 21. Another portion of low-temperature and low-pressure liquid refrigerant flows along the main path (third flow channel 26) into the second feed end of the first heat exchanger 12. This portion of liquid refrigerant is also converted into gaseous refrigerant through heat exchange, and then flows back to the feed end of the second compressor 21, thus completing the cycle. After starting the second refrigeration module 2, the first refrigeration module 1 is started. The high-temperature and high-pressure refrigeration steam discharged from the first compressor 11 enters the first heat exchanger 12 and exchanges heat with the low-temperature and low-pressure liquid refrigerant discharged from the second refrigeration module 2 into the first heat exchanger 12, and then enters the second heat exchanger 14. The second heat exchanger 14 discharges the medium-temperature, high-pressure refrigerant, which is then converted into a low-temperature, low-pressure liquid refrigerant by the first pressure-reducing element 102. Part of the liquid refrigerant flows back into the second heat exchanger 14 through the fifth pipe 19, and is converted into a gaseous refrigerant by heat exchange with the medium-temperature, high-pressure refrigerant output from the first heat exchanger 12, and then flows back to the feed end of the first compressor 11. Another portion of low-temperature and low-pressure liquid refrigerant enters the evaporator 16 along the main path (third pipeline 17), and this portion of liquid refrigerant is also converted into gaseous refrigerant, and then flows back to the feed end of the first compressor 11, thus circulating.

[0051] In the above structure, the first refrigeration module 1 is continued to be described. The fifth pipe 19 and the sixth pipe 101 can form a bypass branch to balance the pressure at the inlet end of the first compressor 11, avoiding the need to set up a separate bypass branch and reducing structural costs.

[0052] In this embodiment, the first pressure reducing member 102 includes: A first thermal expansion valve 1021 is provided on the third pipe 17; A second thermal expansion valve 1022 is provided on the fifth pipe 19; The second pressure reducing member 201 includes: A third thermal expansion valve 2011 is provided in the third flow passage 26; The fourth thermal expansion valve 2012 is provided in the fifth flow passage 28 .

[0053] Take the first pressure reducing component 102 as an example for explanation: On the one hand, thermal expansion valves are provided on both the third pipe 17 and the fifth pipe 19 to independently control the flow rates of the third pipe 17 and the fifth pipe 19; On the other hand, the connection point between the third pipe 17 and the fifth pipe 19 is not greatly restricted, and the line layout in the refrigeration system can be flexibly performed.

[0054] If there is no second thermal expansion valve 1022 , the connection point between the third pipe 17 and the fifth pipe 19 is greatly restricted, and the fluid must first pass through the first thermal expansion valve 1021 before entering this connection point.

[0055] In this embodiment, the first refrigeration module 1 further includes: A first control valve 103 is provided in the third pipeline 17; A second control valve 104 is provided on the fifth pipeline 19; The second refrigeration module 2 further includes: A third control valve 202 is provided in the third flow channel 26; The fourth control valve 203 is provided in the fifth flow passage 28 .

[0056] Taking the first control valve 103 as an example, the second control valve 104, the third control valve 202 and the fourth control valve 203 refer to this description: the first control valve 103 is used in conjunction with the first pressure reducing component 102. When the refrigeration system stops running, the first control valve 103 can quickly cut off the flow of refrigerant before the first pressure reducing component 102 takes effect, so as to protect the evaporator 16 and other equipment, and realize long-term stable operation of the refrigeration system.

[0057] In some embodiments, for a control valve and a pressure reducing structure that are close to each other (eg, the first control valve 103 and the first thermal expansion valve 1021 ), along the fluid flow direction in the pipeline or flow channel, the fluid first passes through the control valve and then passes through the pressure reducing structure.

[0058] In this embodiment, the first refrigeration module 1 further includes: a seventh pipeline 105, both ends of which are connected to the first pipeline 13 and the feed end of the first compressor 11 respectively; a fifth control valve 106 comprising at least one control sub-valve provided on the seventh pipeline 105; The second refrigeration module 2 further includes: The seventh flow channel 204 has two ends connected to the first flow channel 23 and the feed end of the second compressor 21 respectively; The sixth control valve 205 includes at least one control sub-valve provided on the seventh flow channel 204 .

[0059] The seventh pipe 105 and the fifth control valve 106 are used for illustration, and the seventh flow channel 204 and the sixth control valve 205 refer to this illustration: First, the seventh pipeline 105 can be directly connected to the feed end of the first compressor 11, or can be indirectly connected to the feed end of the first compressor 11 (e.g., through the fourth pipeline 18), which is not limited in this embodiment; Second, the fifth control valve 106 may include two control sub-valves, one of which is a solenoid valve and the other is a bypass valve. The solenoid valve can quickly cut off or connect the seventh pipeline 105 to avoid pressure fluctuations or other problems caused by the slow response speed of the bypass valve; Third, the seventh pipeline 105 constitutes a bypass branch, which is initially in a closed state. When the pressure at the feed end of the first compressor 11 is too low, this bypass branch is opened. This bypass branch can directly lead a portion of the high-temperature and high-pressure refrigeration vapor discharged from the discharge end of the first compressor 11 back to the feed end of the first compressor 11 to balance the pressure at the feed end of the first compressor 11.

[0060] In this embodiment, the sixth pipeline 101 is connected to the feed end of the first compressor 11 through the fourth pipeline 18; The seventh pipeline 105 is connected to the feed end of the first compressor 11 through the fourth pipeline 18 or the sixth pipeline 101; The sixth flow channel 29 is connected to the feed end of the second compressor 21 through the fourth flow channel 27; The seventh flow channel 204 is connected to the feed end of the second compressor 21 through the fourth flow channel 27 or the sixth flow channel 29 .

[0061] The example in which the sixth pipeline 101 is connected to the feed end of the first compressor 11 through the fourth pipeline 18 is used for explanation. Similar descriptions in this embodiment refer to this explanation: the sixth pipeline 101 is not directly connected to the feed end of the first compressor 11. On the one hand, the length of the sixth pipeline 101 can be shortened to reduce the structural cost; on the other hand, it can avoid the disorderly layout of multiple pipelines at the feed end of the first compressor 11, which affects the difficulty of subsequent maintenance.

[0062] In some embodiments, the seventh pipeline 105 is connected to the feed end of the first compressor 11 through the sixth pipeline 101 , and the seventh flow channel 204 is connected to the feed end of the second compressor 21 through the sixth flow channel 29 .

[0063] In this embodiment, the fifth control valve 106 and the sixth control valve 205 each include two control sub-valves connected in series.

[0064] For the description of the control sub-valves, please refer to the above embodiment. This embodiment further clarifies the specific settings of the fifth control valve 106 and the sixth control valve 205.

[0065] In this embodiment, the first refrigeration module 1 further includes: An eighth pipe 107, two ends of which are connected to the fifth pipe 19 and the sixth pipe 101 respectively; a seventh control valve 108 , provided on the eighth pipeline 107 ; The second refrigeration module 2 further includes: The eighth flow channel 206 has two ends connected to the fifth flow channel 28 and the sixth flow channel 29 respectively; The eighth control valve 207 is provided in the eighth flow channel 206 .

[0066] For the description of the seventh control valve 108 and the eighth control valve 207 , please refer to the description of similar control valves in the above embodiment. Taking the seventh control valve 108 as an example, the seventh control valve 108 is mainly provided to control the flow of the eighth pipeline 107 .

[0067] Taking the eighth pipe 107 as an example, the eighth flow channel 206 refers to this description: the eighth pipe 107 is actually a bypass branch. The eighth pipe 107 is initially in a closed state. When the pressure at the feed end of the first compressor 11 is too high, the eighth pipe 107 opens, and part of the liquid refrigerant entering the fifth pipe 19 flows directly through the eighth pipe 107 to the feed end of the first compressor 11 to balance the pressure at the feed end of the first compressor 11; The temperature at the feed end of the first compressor 11 may also be too high. At this time, low-temperature and low-pressure liquid refrigerant can be transported to the feed end of the first compressor 11 through the sixth pipe 101 to cool it down, thereby protecting the first compressor 11 from damage. This replaces the method of achieving the cooling effect by constantly starting and stopping the first compressor 11, thereby saving energy consumption.

[0068] Before the eighth pipeline 107 is installed, the sixth pipeline 101 only transports the gaseous refrigerant output by the second heat exchanger 14 ; after the eighth pipeline 107 is installed, the liquid refrigerant and the gaseous refrigerant merge in the sixth pipeline 101 and are transported to the feed end of the first compressor 11 .

[0069] The position of the connection point between the eighth pipeline 107 and the fifth pipeline 19 in one case is shown in the attached figure, which is also used as an example for explanation. The position of each structure in this application can be adjusted according to actual conditions, and the setting in the attached figure can be regarded as a preferred solution.

[0070] In this embodiment, the first refrigeration module 1 further includes: Storage container 109; A ninth pipeline 1001, both ends of which are connected to the first pipeline 13 and the feed end of the storage container 109 respectively; a ninth control valve 1002 , provided on the ninth pipeline 1001 ; a tenth pipeline 1003, both ends of which are connected to the discharge end of the storage container 109 and the feed end of the first compressor 11 respectively; The tenth control valve 1004 is provided on the tenth pipeline 1003 .

[0071] It should be noted that the first refrigeration module 1 cools the interior of the device, and the second refrigeration module 2 exchanges heat with the first refrigeration module 1. Since there is a high risk of refrigerant pressure in the first compressor 11, the first compressor 11 is used in conjunction with the storage container 109.

[0072] The present application does not limit the second compressor 21 to also be equipped with the storage container 109 , and the configuration method is similar to that in the present embodiment.

[0073] When the pressure in the main circuit of the first refrigeration module 1 is higher than the set pressure, the refrigerant can flow into the storage container 109 to protect the safety of the refrigeration system; when the pressure is lower than the set pressure, the refrigerant can flow from the storage container 109 to the first compressor 11.

[0074] In some embodiments, the ninth control valve 1002 is configured as an energy regulating valve.

[0075] In some embodiments, the tenth control valve 1004 is configured as a one-way valve, which only allows fluid to flow from the storage container 109 to the first compressor 11 , thereby preventing the refrigerant that should flow into the feed end of the first compressor 11 from flowing into the storage container 109 .

[0076] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A waste heat recovery cascade refrigeration method, characterized in that: This is achieved through a cascade refrigeration system, which includes a first refrigeration module and a second refrigeration module; the first refrigeration module includes a first compressor, a first heat exchanger, a second heat exchanger, an evaporator and a first pressure reducing element; The second refrigeration module includes a second compressor, a condenser, a third heat exchanger and a second pressure reducing element; Refrigeration methods include: On the one hand, the first high-temperature and high-pressure refrigeration steam is delivered to the condenser through the second compressor; After the first high-temperature and high-pressure refrigeration steam is converted into the first medium-temperature and high-pressure refrigerant through the condenser, it is transported to the second pressure reducing element through the third heat exchanger; After the first medium-temperature and high-pressure refrigerant is converted into a first low-temperature and low-pressure liquid refrigerant by the second pressure reducing element, a portion of the first low-temperature and low-pressure liquid refrigerant is sent back to the third heat exchanger and converted into a first gaseous refrigerant by heat exchange with the first medium-temperature and high-pressure refrigerant, and the remaining first low-temperature and low-pressure liquid refrigerant is sent to the first heat exchanger and converted into the first gaseous refrigerant by heat exchange treatment; delivering the first gaseous refrigerant to the second compressor; On the other hand, the second high-temperature and high-pressure refrigeration steam is delivered to the first heat exchanger through the first compressor, and is heat-exchanged into the second medium-temperature and high-pressure refrigerant before being delivered to the second heat exchanger; The second heat exchanger sends the second medium-temperature and high-pressure refrigerant to the first pressure reducing element and converts it into a second low-temperature and low-pressure liquid refrigerant; sending part of the second low-temperature, low-pressure liquid refrigerant back to the second heat exchanger and being converted into the second gaseous refrigerant by exchanging heat with the second medium-temperature, high-pressure refrigerant, and sending the remaining second low-temperature, low-pressure liquid refrigerant to the evaporator and being converted into the second gaseous refrigerant by heat exchange treatment; The second gaseous refrigerant is delivered to the first compressor.

2. The waste heat recovery cascade refrigeration method according to claim 1, characterized in that: The first feed end of the first heat exchanger is connected to the discharge end of the first compressor through a first pipeline; The first feed end of the second heat exchanger is connected to the first discharge end of the first heat exchanger through a second pipeline; The evaporator is connected to the first discharge end of the second heat exchanger through a third pipe, and is connected to the feed end of the first compressor through a fourth pipe; The third pipeline is connected to the second feed end of the second heat exchanger through a fifth pipeline; The second discharge end of the second heat exchanger is connected to the feed end of the first compressor through a sixth pipeline; The first pressure reducing member is at least provided on the third pipeline; The feed end of the condenser is connected to the discharge end of the second compressor through a first flow channel; The first feed end of the third heat exchanger is connected to the discharge end of the condenser through a second flow channel; The first discharge end of the third heat exchanger is connected to the second feed end of the first heat exchanger through a third flow channel; The second discharge end of the first heat exchanger is connected to the feed end of the second compressor through a fourth flow channel; The third flow channel is connected to the second feed end of the third heat exchanger through a fifth flow channel; The second discharge end of the third heat exchanger is connected to the feed end of the second compressor through a sixth flow channel; The second pressure reducing component is at least provided in the third flow channel.

3. The waste heat recovery cascade refrigeration method according to claim 2, characterized in that: The first pressure reducing member comprises: a first thermal expansion valve, provided on the third pipeline; a second thermal expansion valve, provided on the fifth pipeline; The second pressure reducing member comprises: a third thermal expansion valve, disposed in the third flow passage; The fourth thermal expansion valve is provided in the fifth flow passage.

4. The waste heat recovery cascade refrigeration method according to claim 2, characterized in that: The first refrigeration module further includes: a first control valve, provided on the third pipeline; a second control valve, provided on the fifth pipeline; The second refrigeration module further includes: a third control valve, disposed in the third flow channel; The fourth control valve is provided in the fifth flow channel.

5. The waste heat recovery cascade refrigeration method according to claim 2, characterized in that: The first refrigeration module further includes: a seventh pipeline, having two ends connected to the first pipeline and the feed end of the first compressor respectively; a fifth control valve, comprising at least one control sub-valve provided on the seventh pipeline; The second refrigeration module further includes: a seventh flow channel, two ends of which are respectively connected to the first flow channel and the feed end of the second compressor; The sixth control valve includes at least one control sub-valve arranged on the seventh flow channel.

6. The waste heat recovery cascade refrigeration method according to claim 5, characterized in that: The sixth pipeline is connected to the feed end of the first compressor through the fourth pipeline; The seventh pipeline is connected to the feed end of the first compressor through the fourth pipeline or the sixth pipeline; The sixth flow channel is connected to the feed end of the second compressor through the fourth flow channel; The seventh flow channel is connected to the feed end of the second compressor through the fourth flow channel or the sixth flow channel.

7. The waste heat recovery cascade refrigeration method according to claim 5, characterized in that: The fifth control valve and the sixth control valve each include two control sub-valves connected in series.

8. The waste heat recovery cascade refrigeration method according to claim 2, characterized in that: The first refrigeration module further includes: an eighth pipeline, having two ends connected to the fifth pipeline and the sixth pipeline respectively; a seventh control valve, provided on the eighth pipeline; The second refrigeration module further includes: an eighth flow channel, having two ends connected to the fifth flow channel and the sixth flow channel respectively; The eighth control valve is provided in the eighth flow channel.

9. The waste heat recovery cascade refrigeration method according to claim 2, characterized in that: The first refrigeration module further includes: Storage containers; a ninth pipeline, having two ends connected to the first pipeline and the feed end of the storage container respectively; a ninth control valve, provided on the ninth pipeline; a tenth pipeline, two ends of which are respectively connected to the discharge end of the storage container and the feed end of the first compressor; The tenth control valve is provided on the tenth pipeline.

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