Direct expansion evaporator with steam ejector capability enhancement

Abstract

A system and method for increasing the refrigeration capacity of a direct expansion refrigeration system having a steam separator and a steam ejector. After the throttling process at the expansion device, the mixture of liquid and steam enters the inlet separator. The steam separator powers the ejector by flashing warm refrigerant liquid from higher temperatures and pressures to lower pressures to generate steam. The colder refrigerant liquid then enters the evaporator coil inlet. In addition, the system stabilizes the superheat degree of outlet steam, and reduces the fluctuation of the superheat degree of the outlet caused by the fact that excessive non-evaporated liquid flows out of a pipeline outlet due to uneven distribution at the inlet.

Description

Technical Field

[0001] This invention relates to a direct expansion refrigeration system. Background Technology

[0002] One disadvantage of direct expansion (DX) refrigeration technology compared to pumped refrigerant supply systems is that the reduced refrigerant flow through the evaporator in order to achieve superheat at the evaporator outlet results in decreased cooling capacity. Summary of the Invention

[0003] This invention is an improvement on the existing DX evaporator, enabling increased heat absorption capacity by increasing the local refrigerant flow rate. The refrigerant liquid flow rate is increased by utilizing a vapor ejector to partially recirculate liquid from the evaporator outlet to the evaporator inlet, pumping / ejecting the refrigerant liquid from a lower pressure to a higher pressure. This ejector is powered by flash vapor generated in an expansion device before the evaporator inlet.

[0004] The invention features a combination of a vapor ejector and a separator that utilizes flash gas generated by throttling to recirculate additional refrigerant liquid from the evaporator outlet to the evaporator inlet. In the DX system, the flash gas generated can account for 5% to 15% or more of the total mass flow rate entering the evaporator. The flash gas is primarily considered a parasitic loss because it does not contribute to the evaporation process (where refrigerant liquid is the critical factor). This invention utilizes the aforementioned flash gas to increase the evaporator's capacity by recirculating additional liquid within the evaporator. The increased liquid has greater internal surface contact with the boiling liquid, thus improving heat transfer. This technology is a regenerative method for enhancing refrigeration capacity using flash gas.

[0005] This invention includes a vapor-liquid separator and a vapor ejector. Following the throttling process, as in a standard refrigeration cycle, the liquid and vapor mixture enters the vapor-liquid separator (hereinafter referred to as the "inlet separator"). The inlet separator generates vapor by flashing the warm refrigerant liquid from a higher temperature and pressure to a lower pressure, powering the ejector. The cooler refrigerant liquid enters the evaporator inlet as in a conventional DX system. The refrigerant evaporated during the throttling process is delivered as a driving flow to the vapor ejector. The vapor ejector draws the cold refrigerant liquid from the evaporator outlet into its side port. The cold refrigerant liquid and the driving vapor flow can be separated at the outlet separator, or both can be delivered from the ejector to the evaporator. Typically, after the cold refrigerant liquid is collected, an expansion valve responsive to refrigerant vapor superheat is used to regulate the liquid flow into the evaporator. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of a standard direct expansion refrigeration system.

[0007] Figure 2 This is a schematic diagram of a direct expansion evaporator with enhanced steam ejector capacity according to an embodiment of the present invention.

[0008] Figure 3 This is a schematic diagram of a direct expansion evaporator with enhanced steam ejector capacity according to another embodiment of the present invention.

[0009] Figure 4 This is a schematic diagram of a direct expansion evaporator with enhanced steam ejector capacity according to another embodiment of the present invention.

[0010] Figure 5 This is a schematic diagram of a direct expansion evaporator with enhanced steam ejector capability according to another embodiment of the present invention.

[0011] Figure 6 This is a schematic diagram of a direct expansion evaporator with enhanced steam ejector capability according to yet another embodiment of the present invention.

[0012] The features in the accompanying drawings are indicated by the following reference numerals: 3. Expansion device; 5. The outlet of the expansion device; 7. Refrigerant lines; 9. Inlet of the inlet separator; 11. Inlet separator; 13. Steam outlet of the inlet separator; 15. Liquid outlet of the inlet separator; 16. Refrigerant lines; 17 Distributor Inlet; 18. Refrigerant lines; 19 Distributors; 20 Distributor-side ports; 21 Distributor outlet; 23 Evaporator inlet; 25. Evaporator; 26. Refrigerant lines; 27. Evaporator outlet; 29. Refrigerant lines; 30. Refrigerant piping; 31. Steam inlet of the ejector; 33. Injector; 35. Liquid inlet of the ejector; 37. Injector outlet; 39. Refrigerant piping; 41. Inlet of the outlet separator; 43. Outlet separator; 45. Liquid outlet of the outlet separator; 46. ​​Refrigerant lines; 47. Steam outlet of the outlet separator; 49. Refrigerant lines; 50 Liquid manifold inlet; 51. Liquid manifold; 53. The first outlet of the liquid manifold; 55. The second outlet of the liquid manifold; 57. Refrigerant lines; 59. The second inlet of the outlet separator; 100 Superheat sensor; 102 Controller; 103 Refrigerant lines. Detailed Implementation

[0013] Figure 1 A typical or standard direct expansion (DX) refrigeration system is demonstrated. High-pressure, cooled refrigerant from a high-pressure receiver enters the evaporator through a thermostatic expansion valve and distributor. The thermostatic expansion valve is regulated (opens or closes) based on the superheat of the outlet vapor, with the aim of generating superheated vapor (superheat ≥ 6°F) to ensure the compressor provides dry suction. However, this is not the case in reality, as unevaporated liquid tends to escape from the evaporator, resulting in a decrease in superheat and causing the thermostatic expansion valve to close slightly, reducing refrigerant flow. This reduces cooling capacity. Furthermore, as... Figure 1 As shown, a suction collector is also needed to capture any liquid and ensure that the compressor provides dry suction.

[0014] As described above, direct expansion systems that use distributors to allocate liquid to all loops of the evaporator are also sensitive to uneven distribution. Uneven distribution causes excess liquid to flow out of some loop outlets, resulting in superheat below the target value. This causes the thermostatic expansion valve to raise the superheat back to the target value at the expense of reduced cooling capacity.

[0015] Figure 2 This shows a portion of the DX cooling system of the present invention, which replaces... Figure 1 The relevant part of the existing direct expansion refrigeration system is outlined with a dashed line. (Refer to...) Figure 2In this embodiment, high-pressure, cooled 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 (referred to herein as the inlet separator), which delivers the vapor flash gas received from the expansion unit to the inlet 31 of ejector 33, while refrigerant liquid 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 for delivering refrigerant liquid to evaporator coil 25. Although an 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 superheated vapor and unevaporated liquid. The superheated vapor is delivered via refrigerant line 29 to suction collector and / or compressor, while the unevaporated liquid is delivered via refrigerant line 30 to the liquid inlet 35 of ejector 33. Sensor 100 measures the temperature and pressure of the superheated vapor and sends it to controller 102 to determine if superheat has been reached. The controller 102 controls the expansion device to open or close based on the superheat determination result.

[0016] Simultaneously, ejector 33 uses flash gas received from outlet 13 of inlet separator 11 to eject or "pump" unevaporated liquid, and outlet 37 of ejector 33 delivers the ejected refrigerant liquid and excess flash gas to inlet 41 of vapor-liquid separator 43 (referred to herein as outlet separator) via refrigerant line 39. Outlet separator 43 separates vapor from liquid and returns liquid to evaporator coil 25 via liquid outlet 45 and corresponding refrigerant line 46. Vapor exits outlet 47 and merges with vapor exiting outlet 27 of evaporator coil 25 via refrigerant line 49. With this arrangement, the DX system of the present invention can supply excess liquid to the evaporator coil to maximize cooling capacity, but excess liquid exiting the evaporator coil is captured, redirected, and reheated before being returned to the evaporator coil, thereby preventing damage to the compressor.

[0017] Figure 3 Showing Figure 2 In a variant of the illustrated embodiment, the liquid outlet 45 of the outlet separator 43 is connected to the side port 20 of the distributor 19 via a refrigerant line 46.

[0018] Figure 4 An alternative embodiment is shown, wherein... Figure 2In the illustrated embodiment, the distributor 19 is replaced by a liquid manifold 51. According to this embodiment, the inlet separator 11 delivers liquid refrigerant to the inlet 50 of the liquid manifold 51 via a refrigerant line 16. The liquid manifold has a first outlet 53 and a second outlet 55. The first outlet 53 is directly or indirectly connected to the evaporator coil 25, and the second outlet 55 is connected via a refrigerant line 57 to the second inlet 59 of the outlet separator 43 for supplying additional excess liquid to the outlet separator 43. Figure 2 As in the previous embodiment, the outlet 45 of the outlet separator 43 is connected to the inlet 23 of the evaporator coil 25 via a refrigerant line 46.

[0019] Figure 5 Showing Figure 4 In a variant of the embodiment shown, the outlet 45 of the outlet separator 43 is directly connected to the liquid manifold 51 via a refrigerant line 46.

[0020] Figure 6 This illustrates an embodiment without an outlet separator, where both liquid and vapor leaving the ejector are sent to the evaporator. (See reference...) Figure 6 In this embodiment, high-pressure, cooled 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 inlet separator 11, which delivers the vapor flash gas received from the expansion unit to the inlet 31 of ejector 33, while refrigerant liquid 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 for delivering refrigerant liquid to evaporator coil 25. Although an 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 superheated vapor and unevaporated liquid. The superheated vapor is delivered via refrigerant line 29 to suction collector and / or compressor, while the unevaporated liquid is delivered via refrigerant line 30 to the liquid inlet 35 of ejector 33. Sensor 100 measures the temperature and pressure of the superheated vapor and sends it to controller 102 to determine if superheat has been reached. The controller 102 controls the expansion device to open or close based on the superheat determination result.

[0021] Meanwhile, the ejector 33 uses the flash gas received from the outlet 13 of the inlet separator 11 to pump / eject unevaporated liquid, and the outlet 37 of the ejector 33 delivers the ejected refrigerant liquid and excess flash gas to the distributor 19.

[0022] Although the inlet separator, ejector, and in Figures 2-5In the embodiments, the outlet separators are shown in the exemplary figures and description as constituting independent structural elements, but two or more of them may optionally be combined into an integrated refrigerant recirculation unit that performs all the functions of the three units.

Claims

1. An apparatus for improving the performance of a direct expansion refrigeration system, the apparatus comprising: - Inlet separator, the inlet separator being adapted to connect to the expansion device outlet of the direct expansion refrigeration system; - An evaporator connected to the liquid outlet of the inlet separator; - An ejector connected to the steam outlet of the inlet separator; - A first refrigerant line, which connects the outlet of the evaporator to the liquid inlet of the ejector. - A second refrigerant line, which connects the evaporator outlet to the compressor. - The inlet separator is configured to simultaneously and continuously supply refrigerant vapor to the ejector and refrigerant liquid to the evaporator. - The ejector is configured to deliver refrigerant vapor and refrigerant liquid to the evaporator.

2. A direct expansion refrigeration system, comprising: Refrigerant lines, which are connected in sequence to the following components: - Expansion device, - Inlet separator, - Evaporator, and - Compressor; The refrigeration system also includes: - An injector connected to the outlet of the inlet separator and the outlet of the evaporator, and - Injector outlet, which is connected to the evaporator; The inlet separator is configured to simultaneously and continuously supply refrigerant vapor to the ejector and refrigerant liquid to the evaporator. The ejector is configured to deliver refrigerant vapor and refrigerant liquid to the evaporator.

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

4. The direct expansion refrigeration system according to claim 2 further includes a heat exchanger connected to the expansion device via the refrigerant pipeline for cooling the refrigerant in the refrigerant pipeline.

5. The direct expansion refrigeration system according to claim 4, wherein, The heat exchanger is a condenser or a gas cooler.

6. A method for increasing the cooling capacity of a direct expansion refrigeration system without causing damage to the compressor from refrigerant liquid, the method comprising the following steps performed simultaneously: Liquid is drawn from the evaporator outlet and delivered to the ejector. Refrigerant vapor is obtained from the inlet separator located upstream of the evaporator and then delivered to the ejector. The refrigerant liquid received from the evaporator is heated using the ejector and the steam received from the inlet separator. All liquid and vapor are obtained from the ejector and delivered to the evaporator.

7. The direct expansion refrigeration system according to claim 2, wherein, The inlet separator and the ejector are combined in an integrated refrigerant recovery unit.

8. The method of claim 4, further comprising obtaining refrigerant liquid from the inlet separator and directly delivering the obtained refrigerant liquid to the distributor of the evaporator.

9. The method according to claim 4, further comprising obtaining refrigerant liquid from the inlet separator and delivering the obtained refrigerant liquid to the evaporator liquid manifold.

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