Direct expansion evaporator coil with ejector capacity boost function for low temperature liquid and energy saving systems

Abstract

A system and method for increasing the refrigeration capacity of an energy efficient direct expansion refrigeration system employing two-phase refrigerant as motive flow for an ejector to recirculate liquid refrigerant to an evaporator. After passing through a throttling process at an expansion device, a mixture of liquid and vapor enters the inlet separator. An optional separator sends two-phase refrigerant (liquid and vapor) to an ejector to drive recirculation of liquid refrigerant to an evaporator and sends liquid refrigerant to the evaporator.

Description

Technical Field

[0001] This invention relates to cryogenic liquids and energy-saving refrigeration systems. Background Technology

[0002] U.S. Patent No. 11,493,245B2 discloses a DX refrigeration system that provides a capacity expansion function through a vapor ejector (steam only) that uses flash vapor generated after an expansion valve to drive the recirculation of unevaporated liquid from a suction manifold. Summary of the Invention

[0003] An apparatus and method for improving the performance of a direct expansion refrigeration system are proposed. The apparatus has... An inlet separator, suitable for connection to the outlet of an expansion unit in a direct expansion refrigeration system. The inlet separator has a liquid refrigerant outlet and a two-phase refrigerant outlet, and an evaporator having an evaporator inlet directly connected to the liquid outlet of the inlet separator. The ejector has a power flow inlet that is directly connected to the two-phase refrigerant outlet of the inlet separator. The evaporator outlet refrigerant line connects to the evaporator outlet at its first end, and branches into an evaporator outlet liquid refrigerant line and an evaporator outlet vapor refrigerant line. The liquid refrigerant line at the evaporator outlet is connected to the side port of the ejector, and the vapor refrigerant line at the evaporator outlet is connected to the compressor. The inlet separator is configured to simultaneously and continuously deliver two-phase refrigerant to the ejector and liquid refrigerant to the evaporator.

[0004] According to an alternative embodiment, the inlet separator can be omitted, and the two-phase refrigerant is fed directly into the ejector. In other embodiments, the inlet separator can deliver liquid refrigerant to the ejector and vaporized refrigerant to the evaporator inlet. Attached Figure Description

[0005] Figure 1 It represents an energy-saving direct expansion (DX) refrigeration system.

[0006] Figure 2 This is a representation of an energy-saving direct expansion evaporator with a two-phase ejector capacity-enhancing function according to an embodiment of the present invention.

[0007] Figure 3 This is an example of an energy-saving direct expansion evaporator with a two-phase ejector capacity-enhancing function according to another embodiment of the present invention.

[0008] Figure 4 This is an example of an energy-saving direct expansion evaporator with a two-phase ejector capacity-enhancing function according to another embodiment of the present invention.

[0009] The features in the accompanying drawings are numbered using the following reference numerals: 3 Expansion device 25 Evaporator 5. Expansion unit outlet; 26. Refrigerant piping 7 Refrigerant piping 27 Evaporator outlet 9. Evaporator inlet; 29. ​​Separator inlet; 29. ​​Refrigerant piping 11 Inlet separator 30 Refrigerant piping 13 Inlet separator two-phase outlet; 31 Ejector two-phase inlet. 15 Inlet separator liquid outlet 33 Ejector 16 Refrigerant piping 35 Injector side port 17 Distributor Inlet 37 Injector Outlet 19 Distributor 100 Superheat Sensor 20 Distributor side port 102 Controller 21 Distributor outlet 103 Refrigerant piping 23 Evaporator Inlet Detailed Implementation Figure 1 An energy-efficient direct expansion (DX) refrigeration system is illustrated. High-pressure, high-temperature liquid refrigerant from a high-pressure receiver enters a subcooler, which lowers the temperature of the liquid refrigerant before it passes through a thermostatic expansion valve and distributor into the evaporator. The thermostatic expansion valve is regulated (open or closed) based on the superheat of the outlet vapor, with the aim of generating superheated vapor (superheat ≥ 6℉) to ensure dry suction of the compressor. However, this is not always the case in practice, as unevaporated liquid tends to escape from the evaporator, causing a decrease in superheat and closure of the thermostatic expansion valve to reduce the refrigerant flow rate. This reduces the cooling capacity.

[0010] Energy-efficient DX systems, which use distributors to allocate liquid to all loops of the evaporator, are also sensitive to uneven distribution. Uneven distribution can cause excessive liquid to flow out of some loop outlets, which will cause the superheat to drop below the target value. This will cause the thermostatic expansion valve to close to reduce the amount of liquid refrigerant entering the evaporator, causing the superheat to rise back to the target value, but at the cost of reduced capacity.

[0011] Because of the low evaporator outlet pressure (e.g., in a refrigeration unit), the mass flow rate of the flash vapor requiring compression is reduced, thus enabling the use of energy-efficient systems to decrease compressor workload and improve overall system efficiency. To address the issue of low-temperature feed liquids, this invention delivers both refrigerant phases to the ejector, instead of only delivering saturated vapor or only delivering subcooled liquid. Therefore, the minimum liquid temperature requirement can be significantly reduced, making it suitable for energy-efficient systems.

[0012] The invention is characterized in that a two-phase or saturated liquid refrigerant is delivered to the ejector after being throttled by an electrically operated expansion valve. For the purposes of this invention, x is the mass of the refrigerant (vapor mass / total mass). By definition, the mass of the saturated liquid is then x=0, since the vapor mass is zero. This invention is applicable to cases where 0.95 ≥ x ≥ 0, preferably 0.75 ≥ x ≥ 0, and more preferably 0.5 ≥ x ≥ 0, where x=0 is saturated liquid, x>0 is two-phase, and x=1 is saturated vapor. According to the invention, the upper limit of x can be about 0.95, which provides good flexibility for current applications.

[0013] The two-phase ejector of this invention generates low pressure and draws sufficient liquid flow from the suction header to create a circulating flow, thereby improving the heat transfer capacity of the evaporator. Using nozzles with a high vapor-to-liquid velocity ratio generates an annular / mist flow sufficient to control the two phases. The nozzles are configured to provide flash time, thus increasing vapor quality and achieving minimum pressure, with velocities ranging from 250 ft / s to 1000 ft / s depending on the refrigerant type and conditions.

[0014] Figure 2 A portion of the energy-saving DX refrigeration system of the present invention is shown, which replaces... Figure 1 The portion of the existing energy-saving DX refrigeration system is outlined with a dashed line. (Reference) Figure 2Liquid refrigerant is delivered to expansion unit 3. The outlet 5 of expansion unit 3 is connected via refrigerant line 7 to the inlet 9 of vapor-liquid separator 11 (also referred to herein as the inlet separator), which delivers the two-phase refrigerant received from the expansion unit to the inlet 31 of ejector 33, while the liquid refrigerant is delivered via refrigerant line 16 to the inlet 17 of distributor 19. Distributor outlet 21 is connected via refrigerant line 26 to evaporator coil 25 to deliver liquid refrigerant to evaporator coil 25. Although evaporator coil is used as an example herein, any type of evaporator can be used in conjunction with this invention. The outlet 27 of evaporator coil 25 produces both superheated vapor and unevaporated liquid. Superheated vapor is delivered via refrigerant line 29 to a suction collector and / or compressor, while unevaporated liquid is delivered via refrigerant line 30 to the side port 35 of ejector 33. Sensor 100 measures the temperature and pressure of the superheated vapor and sends it to controller 102 to determine if a superheated state has been reached. The controller 102 determines whether to open or close the expansion device based on the degree of superheat.

[0015] Meanwhile, the ejector 33 uses the two-phase refrigerant L'+V received from the outlet 13 of the inlet separator 11 as the driving flow of the unevaporated liquid L1, and the outlet 37 of the ejector 33 delivers the entrained refrigerant to the distributor 19.

[0016] Although the inlet separator and ejector are in Figure 2 The components shown and described above constitute separate structural elements, but they can optionally be combined into an integrated refrigerant recovery unit that performs the functions of both units.

[0017] Alternative embodiments according to the invention ( Figure 3 (As indicated in the text), the two-phase refrigerant leaving the expansion valve can be directly sent to the ejector, eliminating the need for an inlet separator.

[0018] according to Figure 4 In another alternative embodiment shown, the saturated liquid (x=0) from the inlet separator can be used as the motive flow for the ejector. After a throttling process via an electric expansion valve, a two-phase mixture of liquid and vapor enters the inlet separator at pressure P1, as in a standard energy-saving refrigeration cycle. Figure 4 As shown. Saturated liquid (L) from the separator enters the ejector at an inlet pressure P1. A small amount of vapor (V) from the inlet separator is directed to the side port of the distributor through a fixed regulating orifice, which can be calculated according to the given application along with the ejector dimensions. Even if saturated liquid (x=0 as referenced above) is used as the power source, the ejector can still be the same two-phase ejector described above, because even a saturated liquid inlet will cause flashing and generate a two-phase mixture as it moves through the ejector. Therefore, the nozzle design needs to handle the two-phase flow as described above.

[0019] According to all the embodiments described herein, the injector accelerates (enthalpy decrease = kinetic energy increase), thereby generating a low-pressure P. min This is indicated by the location of the side opening showing liquid L1. P min It is designed to operate below the suction pressure Ps (the pressure in the suction manifold). Therefore, the refrigerant (mainly liquid) is carried from the bottom of the suction manifold to the side port of the ejector, as shown by L1. The total flow L' + L1 + V enters the distributor and is then evenly distributed to the various loops of the evaporator. It should be noted that... Figure 3 and Figure 4 The embodiment in the diagram removes the standard distribution nozzle or orifice to avoid creating additional back pressure on the ejector. The velocity of the refrigerant mixture at the ejector outlet is sufficient to distribute the flow rate evenly. Although only one distributor is shown in the figure, multiple distributors can also be used, as is the case with high-capacity cooling coils.

[0020] As can be seen, all excess liquid flow L1 from the coil is continuously circulated, and only refrigerant vapor in a superheated state (such as in a direct expansion evaporator) leaves the evaporator coil. The superheat can be approximately 3℉ or lower, whereas in conventional DX evaporators, the superheat is >6℉. If a conventional DX evaporator operates below 6℉, liquid will enter the suction port, which is undesirable. This is where the ejector recirculation method has an advantage, as it actively removes any unevaporated liquid / liquid entering from the suction header and increases the wettability inside the coil, thereby improving cooling capacity. It is also a regeneration method because the ejector is powered by the system's input enthalpy and requires no additional energy. When used in conjunction with an energy-efficient refrigeration system, this invention offers dual advantages. Compared to conventional DX evaporators, the circulated liquid significantly improves the coil's cooling capacity by up to 38%, and the energy savings further enhance system efficiency.

[0021] Similar to conventional DX coils, the superheat is measured at the coil outlet on the suction connector (as shown in the figure), which adjusts the opening of the electric expansion valve to achieve a specified superheat of 2℉ to 3℉.

[0022] The ejector is capable of generating a minimum pressure below the suction port and achieving recirculation using a two-phase refrigerant flow. The two-phase ejector design of this invention is based on inlet pressure P1, kinetic mass flow rate fraction, kinetic flow mass, and back pressure P2. P1 and P2 are... Figure 1 and Figure 2 As shown in the image.

[0023] Although specific embodiments, features, elements, combinations and sub-combinations are disclosed herein, it is expressly believed and disclosed herein that each individual element, each individual feature, and each combination and sub-combination thereof disclosed herein can be combined with each other element, feature, combination and sub-combination disclosed herein.

[0024] Those skilled in the art will understand that changes can be made to the above embodiments without departing from the inventive concept of the invention. Therefore, it should be understood that the invention is not limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as set forth in this disclosure and as defined by the broadest reasonable interpretation of the appended claims, interpreted in conjunction with this specification.

Claims

1. An apparatus for improving the performance of a direct expansion refrigeration system, the apparatus comprising: An inlet separator, adapted to be connected to the outlet of the expansion unit of the direct expansion refrigeration system, the inlet separator having a liquid refrigerant outlet and a two-phase refrigerant outlet. An evaporator having an evaporator inlet that is directly connected to the liquid outlet of the inlet separator. The ejector has a power flow inlet that is directly connected to the two-phase refrigerant outlet of the inlet separator. An evaporator outlet refrigerant line is provided, which is connected to the outlet of the evaporator at a first end. The evaporator outlet has an evaporator outlet liquid refrigerant line and an evaporator outlet vapor refrigerant line. The liquid refrigerant line at the evaporator outlet is connected to the side port of the ejector. The evaporator outlet refrigerant vapor line is connected to the compressor. The inlet separator is configured to simultaneously and continuously deliver two-phase refrigerant to the ejector and liquid refrigerant to the evaporator.

2. The apparatus of claim 1, wherein the inlet separator is configured to simultaneously and continuously deliver two-phase refrigerant directly to the ejector and to deliver liquid refrigerant directly to the evaporator via the evaporator inlet.

3. The device according to claim 1, wherein the inlet separator and the ejector are combined in an integrated refrigerant recovery unit.

4. The device according to claim 1, wherein the evaporator inlet is a distributor or a liquid manifold.

5. A direct expansion refrigeration system, comprising: Refrigerant piping, wherein the refrigerant piping is connected to the following in refrigerant flow sequence: Expansion device, Inlet separator, Injector; Evaporator, and compressor, The inlet separator is configured to simultaneously and continuously i) deliver two-phase refrigerant to the ejector, and ii) deliver liquid refrigerant directly to the inlet of the evaporator.

6. The direct expansion refrigeration system of claim 5, wherein the inlet separator and the ejector are combined in an integrated refrigerant recovery unit.

7. An apparatus for improving the performance of a direct expansion refrigeration system, the apparatus comprising: A two-phase ejector, the two-phase ejector having: a power flow inlet, the power flow inlet being directly connected to the expansion device outlet of the direct expansion refrigeration system; An ejector side port, which is connected to the outlet of the evaporator; and a two-phase outlet, which is directly connected to the inlet of the evaporator; The evaporator has an outlet vapor refrigerant line connected to the compressor.

8. A direct expansion refrigeration system, comprising: Refrigerant piping, wherein the refrigerant piping is connected to the following in refrigerant flow sequence: Expansion device, Injector; Evaporator, and compressor, The expansion device is configured to deliver two-phase refrigerant to the power flow inlet of the ejector, the evaporator is configured to deliver liquid refrigerant to the recirculation liquid inlet of the ejector, and the ejector is configured to deliver two-phase refrigerant to the evaporator.

9. An apparatus for improving the performance of a direct expansion refrigeration system, the apparatus comprising: An inlet separator, adapted to be connected to the outlet of the expansion unit of the direct expansion refrigeration system, the inlet separator having a liquid refrigerant outlet and a vapor refrigerant outlet. An evaporator having an evaporator inlet that is directly connected to the steam outlet of the inlet separator. An ejector having a power flow inlet directly connected to the liquid refrigerant outlet of the inlet separator. The evaporator outlet manifold includes a refrigerant line for a vapor outlet and a refrigerant line for a liquid outlet. The liquid refrigerant line at the outlet of the evaporator outlet manifold is connected to the recirculation liquid inlet of the ejector. The evaporator outlet manifold, vapor outlet, and refrigerant line are connected to the compressor. The inlet separator is configured to simultaneously and continuously deliver vapor refrigerant to the evaporator inlet and liquid refrigerant to the ejector.

10. A direct expansion refrigeration system, comprising: Refrigerant piping, wherein the refrigerant piping is connected to the following in refrigerant flow sequence: Expansion device, Inlet separator, Injector; Evaporator, and compressor, The inlet separator is configured to simultaneously and continuously i) deliver liquid refrigerant to the ejector and ii) deliver vapor refrigerant to the inlet of the evaporator.

11. A method for increasing the cooling capacity of a direct expansion refrigeration system without the risk of damaging the compressor, comprising the following steps: Liquid is drawn from the evaporator outlet and delivered directly to the ejector. Two-phase refrigerant is drawn from an inlet separator located immediately adjacent to the evaporator inlet and upstream of the ejector, and the two-phase refrigerant is delivered to the ejector. The two-phase refrigerant is used to drive the liquid refrigerant received from the evaporator back to the evaporator through the ejector.

12. The method of claim 11, further comprising drawing refrigerant liquid from the inlet separator and delivering it directly to the inlet of the evaporator.

13. A method for increasing the cooling capacity of a direct expansion refrigeration system without the risk of damaging the compressor, comprising the following steps: Liquid is drawn from the evaporator outlet and delivered directly to the ejector. Two-phase refrigerant is directly drawn from the expansion unit and delivered to the ejector. The two-phase refrigerant is used to drive the liquid refrigerant received from the evaporator back to the evaporator through the ejector.

14. A method for increasing the cooling capacity of a direct expansion refrigeration system without the risk of damaging the compressor, comprising the following steps: Liquid is drawn from the evaporator outlet and delivered directly to the ejector. Liquid refrigerant is drawn from an inlet separator located immediately upstream of the evaporator and the ejector, and the liquid refrigerant is delivered to the power flow inlet of the ejector. The liquid refrigerant is used to drive the recirculated liquid refrigerant received from the evaporator back to the evaporator through the ejector.

15. The apparatus according to any one of claims 1, 7 and 9, wherein the evaporator inlet includes a distributor.

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