Oil separator and return device for injector-based direct expansion (DX) evaporator

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 generates steam to power the ejector by flashing warm refrigerant liquid from a higher temperature and pressure to a lower pressure. The lower temperature refrigerant liquid then enters an evaporator coil inlet. The vapor and refrigerant vapor from the evaporator outlet enter the ejector together. The ejector delivers oil and vapor as well as liquid refrigerant to the oil separator, which returns oil to the compressor and delivers liquid and vapor refrigerant to the evaporator.

Description

Background Art Technical Field

[0001] The present invention relates to a direct expansion evaporator refrigeration system

[0002] Background Description

[0003] In a refrigeration cycle, refrigerant oil is used to lubricate the internal moving parts of a compressor, cool, and enable good sealing. Even with good oil separation, a very small portion of the oil is carried by the refrigerant throughout the system and accumulates in the suction header of the evaporator. The oil must be removed from the evaporator and returned to the compressor. When the refrigeration cycle utilizes hot gas defrosting, oil return is typically achieved. However, not all systems are equipped with hot gas defrosting. Summary of the Invention

[0004] The cooling capacity of an ejector DX evaporator is up to 38% higher than that of a conventional DX. This increase in cooling capacity is achieved by recirculating liquid refrigerant from the suction header back to the distributor using an ejector, and superheated steam is discharged from the top suction connector similar to a DX evaporator. This causes a potential problem of refrigerant oil recirculating back and potentially accumulating in the evaporator coil. The object of the present invention is to alleviate this potential problem by separating and collecting refrigerant oil from the refrigerant downstream of the ejector and intermittently returning it to the suction connector. Brief Description of the Drawings

[0005] The foregoing Summary of the Invention, as well as the following detailed description of the preferred invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the present invention, the presently preferred embodiments are shown in the drawings. However, it should be understood that the present invention is not limited to the precise arrangements and means shown. In the drawings:

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

[0007] Figure 2 is a schematic diagram of a direct expansion evaporator with steam ejector capacity enhancement (ejector DX evaporator).

[0008] Figure 3 Shows a schematic diagram of an ejector DX evaporator and an oil separator / collector according to an embodiment of the present invention at the outlet of the ejector.

[0009] Figure 4 Shows an oil separator / collector according to an embodiment of the present invention.

[0010] Figure 5 is an auxiliary ejector bridged between the outlet port and the LC according to an embodiment of the present invention.

[0011] The features in the accompanying drawings are numbered with the following reference numerals:

[0012] 3 Expansion device.

[0013] 5 Expansion device outlet

[0014] 7 Refrigerant pipeline

[0015] 9 Inlet to inlet separator

[0016] 11 Inlet separator

[0017] 13 Inlet separator steam outlet

[0018] 15 Inlet separator liquid outlet

[0019] 16 Refrigerant pipeline

[0020] 17 Distributor inlet

[0021] 18 Refrigerant pipeline

[0022] 19 Distributor

[0023] 21 Distributor outlet

[0024] 23 Evaporator inlet

[0025] 25 Evaporator

[0026] 26 Refrigerant pipeline

[0027] 27 Evaporator outlet

[0028] 29 Refrigerant pipeline

[0029] 30 Refrigerant pipeline

[0030] 31 Ejector steam inlet

[0031] 33 Ejector

[0032] 35 Ejector liquid inlet

[0033] 37 Ejector outlet

[0034] 39 Refrigerant pipeline

[0035] 41 Outlet separator inlet

[0036] 46 Refrigerant pipeline

[0037] 57 Refrigerant pipeline

[0038] 100 Overheat sensor

[0039] 102 Controller

[0040] 103 Refrigerant pipeline DETAILED IMPLEMENTATION MANNER

[0041] Figure 1 illustrates a typical standard direct expansion (DX) refrigeration system. The high-pressure cooled refrigerant from the high-pressure receiver enters the evaporator through a thermostatic expansion valve and a distributor. The thermostatic expansion valve is adjusted (opened or closed) based on the superheat of the outlet steam, aiming to produce superheated steam (superheat ≥ 6°F) to ensure dry suction of the compressor. However, in practice, this is not the case because the unevaporated liquid tends to escape from the evaporator, resulting in a decrease in superheat and the closing of the thermostatic expansion valve to reduce the refrigerant flow rate. This reduces the refrigeration capacity. In addition, a suction trap as shown in Figure 1 is required to trap any liquid and ensure dry suction of the compressor.

[0042] For the DX system as described above, which uses a distributor to distribute the liquid to all circuits of the evaporator, all circuits of the evaporator are also sensitive to uneven distribution. Uneven distribution causes excessive liquid to flow out of the outlets of some circuits, which will reduce the superheat below the target. This causes the thermostatic expansion valve to increase the superheat back to the target value at the expense of reducing the capacity.

[0043] Figure 2 illustrates a portion of the DX refrigeration system that replaces the portion of the DX refrigeration system enclosed by the dashed line in Figure 1 , specifically including an ejector DX evaporator (U.S. Patent No. 11,349,324 and U.S. Serial No. 18 / 350,739, the entire contents of which are incorporated herein by reference). The ejector is a fluid enthalpy pump powered by refrigerant vapor, and the ejector recirculates the refrigerant liquid (L1) from the bottom of the suction header back to the side port of the distributor, as shown. Therefore, the evaporator operates under "oversupply" conditions, resulting in increased cooling capacity, while the fluid discharged from the suction connector is superheated steam without liquid carryover like traditional DX.

[0044] See Figure 2, high-pressure, cooled refrigerant is delivered to expansion device 3. The outlet 5 of expansion device 3 is connected via refrigerant line 7 to the inlet 9 of inlet separator 11, which sends the flashed vapor received from the expansion device to the inlet 31 of ejector 33, while the liquid refrigerant is sent via refrigerant line 16 from the outlet 15 of the inlet separator to the inlet 17 of distributor 19. The distributor outlet 21 is connected via refrigerant line 26 to evaporator coil 25 for delivering the refrigerant liquid to the evaporator inlet 23 of evaporator coil 25. Although an evaporator coil is used as an example herein, any type of evaporator may be used in combination with the present invention. The outlet 27 of evaporator coil 25 produces superheated vapor and unevaporated liquid. The superheated vapor is sent via refrigerant line 29 to the suction trap and / or compressor, and the unevaporated liquid is sent 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 them to controller 102 to determine whether superheat has been achieved. Controller 102 opens or closes the expansion device based on the superheat determination.

[0045] Meanwhile, ejector 33 pumps / entrains the unevaporated liquid using the flashed gas received from the outlet 13 of inlet separator 11 via refrigerant line 18, and the outlet 37 of ejector 33 delivers the entrained refrigerant liquid and excess flashed gas via refrigerant line 46 to distributor 19.

[0046] Figure 3 Shows a schematic of an ejector DX evaporator similar to Figure 2 but having an oil separator / collector 301 at the outlet of ejector 33 according to the present invention. The present invention is necessary for an ejector DX evaporator not equipped with hot gas (HG) defrost to return oil to the compressor. That is, the ejector DX circuit is bottom-fed, which enables oil return during hot gas defrost. In this case, hot gas is pumped through the suction connector into the suction header and into the coil. The condensate formed by defrost is drained through the circuit into the distributor and finally out of the side port of the distributor. The refrigerant oil in the coil is also pushed out through the side port of the distributor along with the condensate and the hot gas.

[0047] However, for an ejector DX without HG defrost, there is a possibility of oil accumulation in the coil due to the recirculation of liquid refrigerant from the suction header and the absence of an active device to return the oil. The present invention is particularly applicable to applications such as Figure 3 shown for separating, collecting the refrigerant oil and intermittently returning it to the suction connector. The present invention is specifically aimed at applications for separating, collecting and intermittently returning the refrigerant oil to the suction connector, as Figure 3 shown.

[0048] Figure 4 Figure 301 shows an oil separator / collector according to an embodiment of the present invention. It has two chambers, an upper part (UC) 303 and a lower part (LC) 305, where the hollow float 6 returns. The oil separator also has an inlet port 311, an outlet port 313, and an oil return line 315 at the bottom. The inlet port 311 of the UC 303 receives steam + liquid refrigerant + oil from the main injector 33, as Figure 3 shown. The UC 303 has a long dip tube 317 leading to the LC 305. The liquid / oil denser than the steam quickly enters the LC 305 through the dip tube 317. This is a separation or stratification technique for moving the denser oil / oil-rich refrigerant to the bottom of the LC 305, while the lighter refrigerant moves to the top of the LC. On the other hand, the steam enters the auxiliary injector 319 as shown, which bridges the LC 305 to the outlet port 313 of the oil separator. The auxiliary injector 319 (described below) is operated by steam power, and its entrainment tube 321 is connected to the top of the LC 305, as shown. When the steam power moves through the auxiliary injector 319, it draws liquid from the top of the LC 305, and the steam-liquid mixture is discharged through the outlet port 313 to the distributor side port, as Figure 3 shown. The denser oil / oil-rich liquid remains on the bottom of the LC 305 and gradually builds up the liquid level because the LC 305 is very static with little fluid movement. As the liquid level of the oil-rich refrigerant builds up in the LC 305, the float 307 is designed to open due to buoyancy when the liquid level exceeds about 75% of the height of the float. When the float is lifted, a small amount of oil leaves through the orifice 309 at the bottom and enters the suction connector.

[0049] The present invention is particularly suitable for liquid refrigerants having a lower density than refrigerant oil. Examples are ammonia refrigerant and FES#1 compressor oil having a specific gravity of 0.87.

[0050] Figure 5 A schematic diagram of the auxiliary injector is shown in. The function of the auxiliary injector 319 is to remove oil-free liquid refrigerant (when present) from the top of the LC 305. It operates by using motive steam and at a very low pressure drop (preferably 0.5 psi or less). The auxiliary injector 319 has an annular channel 323 for the vapor to increase its velocity, while the liquid refrigerant is entrained from the central entrainment tube 321 connected to the top of the LC 305. The typical mass flow entrainment ratio of such a device is 2 to 3, exceeding the entrainment ratio of the main injector 33, so that the liquid refrigerant does not flood the UC 303.

[0051] The efficacy of this oil separator 301 lies in the fact that the liquid refrigerant / oil mixture tends to be drawn into the LC 305 through the long dip tube 317, while the vapor moves quickly through the ejector port to the outlet. The lighter liquid refrigerant then floats to the top of the LC 305 by gravity, while the oil / oil-rich refrigerant tends to move to the bottom. The addition of the auxiliary ejector 319 ensures that the lighter liquid can be skimmed from the top of the LC 305, while providing sufficient settling time for the oil to separate out and collect at the bottom.

[0052] Once a sufficient oil level is collected, the float valve is lifted by buoyancy and discharges the oil through the orifice into the suction connector.

[0053] Several prototypes have included full-scale prototypes that handle steam flows of over 1 lb / minute and liquid flows of over 2 lb / minute. These flow rates are the maximum expected from large cooling capacity evaporator coils (e.g., 50 TR).

[0054] Those skilled in the art will understand that changes can be made to the above preferred embodiments without departing from the inventive concept thereof. Thus, it is understood that the present invention is not limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention outlined in this disclosure and as defined by the broadest reasonable interpretation of the appended claims read in light of 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 an expansion device of the direct expansion refrigeration system, An evaporator connected to the liquid outlet of the inlet separator, An ejector connected to the vapor outlet of the inlet separator, A first refrigeration pipeline connecting the first outlet of the evaporator to the liquid inlet of the ejector, A second refrigeration pipeline connecting the second outlet of the evaporator to a compressor, An oil separator connected to the outlet of the ejector; A third refrigeration pipeline connecting the first outlet of the oil separator to the compressor; A fourth refrigeration pipeline connecting the second outlet of the oil separator to the evaporator; The inlet separator is configured to simultaneously and continuously deliver refrigerant vapor to the ejector and deliver refrigerant liquid to the evaporator, the ejector is configured to deliver oil, refrigerant vapor and refrigerant liquid to the oil separator, and the oil separator is configured to deliver oil to the compressor and deliver refrigerant vapor and refrigerant liquid to the evaporator.

2. The device according to claim 1, wherein The oil separator includes a vertically oriented tube having an upper chamber and a lower chamber, the upper chamber having an upper chamber inlet port and an upper chamber outlet port, and the lower chamber having a float located above an oil return outlet; The upper chamber is connected to the lower chamber through an immersion tube configured to allow oil, liquid refrigerant and liquid refrigerant to enter the lower chamber; And an inlet tube for the auxiliary ejector for allowing liquid refrigerant to enter the auxiliary ejector from the lower chamber.

3. The direct expansion refrigeration system according to any one of the preceding claims, wherein, The inlet separator and the ejector are combined in an integrated refrigerant recirculation device.

4. The direct expansion refrigeration system according to any one of the preceding claims, further comprising a heat exchanger connected to the expansion device through the refrigerant pipeline for cooling the refrigerant in the refrigerant pipeline.

5. The direct expansion refrigeration system according to any one of the preceding claims, wherein, The heat exchanger is a condenser or a gas cooler.

6. A direct expansion refrigeration system, comprising: A refrigerant pipeline sequentially connecting the following components: An expansion device, An inlet separator, An evaporator, and A compressor, The refrigeration system further comprises An ejector connected to the outlet of the inlet separator and the outlet of the evaporator, and An ejector outlet connected to an oil separator having a first outlet configured to return oil to the compressor and a second outlet for delivering liquid refrigerant and vapor refrigerant to the evaporator; The inlet separator is configured to simultaneously and continuously deliver refrigerant vapor to the ejector and deliver refrigerant liquid to the evaporator.

7. The direct expansion refrigeration system according to claim 6, wherein the oil separator comprises a vertically oriented tube having an upper chamber and a lower chamber, the upper chamber having an upper chamber inlet port and an upper chamber outlet port, and the lower chamber having a float located above an oil return outlet; The upper chamber is connected to the lower chamber through an immersion tube configured to allow oil, liquid refrigerant, and liquid refrigerant to enter the lower chamber; And an inlet tube for the auxiliary ejector, the inlet tube being configured to allow liquid refrigerant to enter the auxiliary ejector from the lower chamber.

8. The direct expansion refrigeration system according to any one of claims 6 and 7, wherein The inlet separator and the ejector are combined in an integrated refrigerant recirculation device.

9. The direct expansion refrigeration system according to any one of claims 6 to 8, further comprising a heat exchanger connected to the expansion device through the refrigerant pipeline for cooling the refrigerant in the refrigerant pipeline.

10. The direct expansion refrigeration system according to any one of claims 6 to 9, wherein, The heat exchanger is a condenser or a gas cooler.

11. A method for increasing the refrigeration capacity of a direct expansion refrigeration system, comprising the following steps: Obtaining liquid from the outlet of the evaporator and delivering the liquid to the ejector, Obtaining refrigerant vapor from an inlet separator located upstream of the evaporator and delivering the obtained refrigerant vapor to the ejector, Using the ejector to heat together the vapor received from the inlet separator and the refrigerant liquid received from the evaporator; Delivering liquid refrigerant, vapor refrigerant, and oil from the ejector and delivering the liquid refrigerant, vapor refrigerant, and oil to the oil separator; Delivering oil from the oil separator to the compressor, Delivering liquid refrigerant and vapor refrigerant from the oil separator to the evaporator.

12. The method according to claim 11, further comprising allowing the oil to settle in the lower chamber of the oil separator below the liquid refrigerant level, and using an auxiliary ejector located in the upper chamber containing vapor refrigerant, and using the vapor refrigerant in the auxiliary ejector as power to entrain the liquid refrigerant from the lower chamber into the feed pipe of the auxiliary ejector to drive the liquid refrigerant and the vapor refrigerant from the oil separator to the evaporator.

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