Lubricating oil cooling subsystem in compressor refrigeration system

Abstract

The present invention discloses a lubricating oil cooling subsystem in a compressor refrigeration system, which belongs to the field of refrigeration technology. The refrigerant inlet of the oil-cooled heat exchanger connected to the compressor unit is used to connect to the evaporative condenser drain pipe, and the refrigerant outlet is connected to a horizontal gas-liquid separation pipe. The gas-liquid separation pipe is respectively connected to a return liquid pipe and a return air pipe. The return liquid pipe is used to connect to the evaporative condenser drain pipe, and the connection position between the return liquid pipe and the evaporative condenser drain pipe is lower than the gas-liquid separation pipe. The return air pipe is connected to a balance pipe, and the connection position between the return air pipe and the balance pipe is higher than the gas-liquid separation pipe. The connection position between the oil-cooled refrigerant inlet pipe and the evaporative condenser drain pipe is lower than the gas-liquid separation pipe. Not only is the length of the refrigerant discharge pipeline of the oil-cooled heat exchanger shortened and the refrigerant filling amount reduced, but gas-liquid separation is also performed, the liquid phase is discharged in advance, and only the gas phase returns to the evaporative condenser, thereby increasing the refrigerant flow rate and achieving a better oil cooling effect.

Description

Technical Field

[0001] The invention relates to a lubricating oil cooling subsystem in a refrigeration system, belonging to the technical field of refrigeration. Background Art

[0002] Lubricant oil cooling in compressor refrigeration systems is critical to the operating efficiency and service life of refrigeration systems and compressor units. Inadequate oil cooling can lead to a number of problems, including the following: First, increased lubricant oil temperature reduces viscosity, thinning or even breaking the oil film, resulting in poor lubrication of moving parts and increased wear. Second, operating the unit at excessively high temperatures accelerates lubricant oil oxidation, forming carbon deposits or sludge, further deteriorating lubrication conditions. Third, increased exhaust gas temperatures increase the risk of system overheating, potentially triggering a high-pressure shutdown and disrupting normal production. Fourth, during shutdown, high-temperature lubricant oil dissolves more refrigerant, causing a sudden release of refrigerant upon unit restart, potentially causing liquid hammer or transient refrigerant starvation, reducing cooling capacity. Fifth, poor lubrication and high-temperature operation increase friction losses, leading to increased compressor power consumption and a decrease in the system's Coefficient of Performance (COP), a key metric for measuring the energy efficiency of compressors or refrigeration / heat pump systems, indicating the cooling or heating capacity delivered per unit of energy consumed. Sixth, certain synthetic oils (such as POE) decompose easily at high temperatures to produce acidic substances that corrode unit components. Seventh, the high temperature of lubricating oil causes the refrigerant to decompose thermally and produce non-condensable gases, which affects the refrigeration efficiency of the system.

[0003] As an existing technology, the main measures to improve the oil cooling effect include: regularly cleaning the oil cooler; trying to choose synthetic lubricants with good high temperature resistance and antioxidant stability; controlling the exhaust temperature by adding liquid spray cooling and other methods, etc.

[0004] Currently, the most ideal method for cooling lubricating oil in compressor refrigeration systems is to use liquid refrigerant through an oil-cooled heat exchanger. In the specific oil cooling subsystem, the liquid refrigerant, after exiting the oil-cooled heat exchanger, forms a vapor-liquid two-phase flow. This flow then flows through a connecting pipe into a siphon tank or an evaporative condenser with vapor-liquid diversion functionality, separating the gas and liquid phases. The gas phase is then drawn into the condensing heat exchanger of the evaporative condenser, where it condenses, dissipating heat to the surrounding environment. The gas phase refrigerant then condenses back into liquid for circulating refrigeration.

[0005] The above-mentioned method of using liquid refrigerant to cool the lubricating oil through an oil-cooled heat exchanger has a major disadvantage: after the liquid refrigerant flowing through the oil-cooled heat exchanger is heated by the high-temperature lubricating oil, the refrigerant flowing out is a mixture of gas and liquid phases. The distance between the refrigerant outlet of the oil-cooled heat exchanger and the liquid inlet of the siphon tank or the refrigerant inlet of the oil-cooled heat exchanger with vapor-liquid diversion is long, and both inlets are located at high altitudes. In large refrigeration systems with multiple oil-cooled heat exchangers, the liquid outlet pipes of the oil-cooled heat exchangers are connected in parallel, with pipe lengths varying significantly. This results in significant variations in the cooling efficiency of the lubricating oil from each oil-cooled heat exchanger. Especially in high summer temperatures, the condensing efficiency of the evaporative condenser decreases, increasing the exhaust temperature of the refrigeration compressor. Oil-cooled heat exchangers with longer connecting pipes experience poor cooling efficiency and higher oil temperatures, resulting in reduced load on the refrigeration compressor, which can severely impact normal production.

[0006] Chinese patent application CN114396373A discloses an "oil cooling subsystem for an evaporative condenser." This system organically integrates an oil-cooled heat exchanger with an evaporative condenser. The system utilizes pressure differences between the oil-cooled heat exchanger and the composite header, and between the oil-cooled heat exchanger and the secondary heat exchange header to create a natural flow of refrigerant within the oil-cooled heat exchanger. This eliminates the need for a siphon tank and improves the cooling efficiency of the oil-cooled heat exchanger. This eliminates the need for a siphon tank without compromising the condensing efficiency of the evaporative condenser. In this patent application, the refrigerant outlet end of the oil-cooled heat exchanger is connected to the composite manifold, the secondary steam inlet manifold of the condensing heat exchanger or respectively to the composite manifold and the secondary steam inlet manifold of the condensing heat exchanger through a refrigerant liquid outlet pipe, that is, there is a longer pipeline between the oil-cooled heat exchanger and the condensing heat exchanger. On the one hand, the pipeline increases the use and maintenance costs of the system pipes and valves, and leads to an increase in the amount of refrigerant added to the system. Since the refrigerant is expensive, the operating cost of the system is further increased; on the other hand, since the refrigerant flowing out of the oil-cooled heat exchanger is a vapor-liquid mixed phase, the flow resistance in the pipeline is large and the speed is slow, which affects the oil cooling effect. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a lubricating oil cooling subsystem in a compressor refrigeration system. First, the length of the gas-liquid two-phase flow pipeline of the refrigerant discharge of the oil-cooled heat exchanger is further shortened to reduce the amount of refrigerant added and increase its flow rate; second, by performing gas-liquid separation in the refrigerant discharge pipeline of the oil-cooled heat exchanger, the liquid phase is discharged in advance, and only the gas phase returns to the evaporative condenser, so as to greatly increase the refrigerant flow rate and achieve a better oil cooling effect.

[0008] The technical solutions of the present invention are as follows:

[0009] The lubricating oil cooling subsystem in the compressor refrigeration system includes a compressor unit and an oil-cooled heat exchanger connected to the compressor unit, and also includes a liquid reservoir for connecting the discharge end of the evaporative condenser heat exchanger through the evaporative condenser discharge pipe and a balance pipe with an upper end for connecting the evaporative condenser heat exchanger and a lower end connected to the liquid reservoir. The exhaust end of the compressor unit is used to connect the steam inlet end of the evaporative condenser heat exchanger, the refrigerant inlet end of the oil-cooled heat exchanger is used to connect the evaporative condenser discharge pipe through the oil-cooled refrigerant inlet pipe, and the oil-cooled heat exchanger is connected to the evaporative condenser discharge pipe. The refrigerant outlet end is connected to a horizontal gas-liquid separation tube through an oil-cooled refrigerant outlet pipe; the other end of the gas-liquid separation tube is respectively connected to a return liquid pipe and a return air pipe; the other end of the return liquid pipe is connected to the evaporative condenser drain pipe or the oil-cooled refrigerant inlet pipe, and the connection position between the return liquid pipe and the evaporative condenser drain pipe is lower than the gas-liquid separation tube; the other end of the return air pipe is connected to the balance pipe, and the connection position between the return air pipe and the balance pipe is higher than the gas-liquid separation tube; the connection position between the oil-cooled refrigerant inlet pipe and the evaporative condenser drain pipe is lower than the gas-liquid separation tube.

[0010] Preferably, the upper end of the balance pipe is connected to the steam inlet end of the evaporative condenser heat exchanger.

[0011] Preferably, the evaporative condenser heat exchanger has more than two stages of heat exchangers; the upper end of the balancing pipe is connected to the intermediate steam inlet header of the evaporative condenser heat exchanger.

[0012] Preferably, the subsystem further comprises a transition pipe; the upper end of the transition pipe is connected to the drain pipe of the evaporative condenser; the refrigerant inlet end of the oil-cooled heat exchanger is connected to the lower end of the transition pipe through the oil-cooled refrigerant inlet pipe.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] First, the present invention achieves gas-liquid separation in the gas-liquid separation tube, through the combined action of the gas-liquid separation tube, the liquid return tube, the gas return tube, and the balancing tube. This achieves separation and diversion of the gas-liquid two-phase flow within the tube. This diversion process is accompanied by flash evaporation, enabling more efficient cooling of the refrigerant liquid. Furthermore, after the gas-liquid diversion, the gas-phase refrigerant and the liquid-phase refrigerant flow in separate tubes. The liquid flows into the liquid reservoir in advance, or flows back into the refrigerant inlet tube of the oil-cooled heat exchanger to further cool the lubricating oil, achieving more efficient circulating cooling.

[0015] Second, the refrigerant discharge line of the oil-cooled heat exchanger of the present invention is connected to the system's existing balancing pipe, sharing the same conduit. This effectively shortens the length of the refrigerant discharge line for the oil-cooled heat exchanger's gas-liquid two-phase flow, reducing the amount of refrigerant injected. Furthermore, the suction force of the balancing pipe draws the separated gas-phase refrigerant into the evaporative condenser, allowing for smoother flow separation of the gas-liquid two-phase refrigerant. Furthermore, since the separate gas-phase refrigerant has low flow resistance and a higher flow rate, the refrigerant flow rate through the oil-cooled heat exchanger is significantly increased, resulting in a better oil cooling effect.

[0016] Third, for large-scale refrigeration systems with two or more oil-cooled heat exchangers, the present invention separates and diverts the gas-liquid flow in each oil-cooled heat exchanger. The gas phase pipelines are then connected in parallel and introduced into the evaporative condenser via a balancing pipe. Because the pure gas phase has low flow resistance in the pipeline, this solves the technical problem of varying oil cooling effects due to unequal distances. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure and working principle of embodiment 1 of the present invention.

[0018] Figure 2 It is a schematic diagram of the structure and working principle of embodiment 2 of the present invention.

[0019] Figure 3 It is a schematic diagram of the structure and working principle of embodiment 3 of the present invention.

[0020] Description of reference numerals:

[0021] 1. Compressor unit; 2. Oil-cooled heat exchanger; 3. Oil-cooled refrigerant inlet pipe; 4. Oil-cooled refrigerant outlet pipe; 5. Gas-liquid separator pipe; 6. Evaporative condenser drain pipe; 7. Liquid return pipe; 8. Gas return pipe; 9. Balancing pipe; 10. Liquid reservoir; 11. Liquid reservoir supply pipe; 12. Evaporative condenser heat exchanger; 13. Evaporative condenser; 14. Compressor exhaust pipe; 15. Transition pipe; 16. Oil drain pipe. DETAILED DESCRIPTION

[0022] The present invention is further described below with reference to the accompanying drawings and examples.

[0023] Example 1

[0024] This embodiment relates to a refrigeration system having an oil-cooled heat exchanger.

[0025] like Figure 1The system of this embodiment includes a compressor unit 1 and an evaporative condenser 13. The evaporative condenser 13 includes a housing and an evaporative condenser heat exchanger 12 installed in the housing. In this embodiment, the evaporative condenser 13 also includes a circulating fan and a circulating water pump. The evaporative condenser heat exchanger 12 dissipates heat by spraying water evaporation.

[0026] The steam inlet of the evaporative condenser heat exchanger 12 is connected to the exhaust of the compressor unit 1 via a compressor exhaust pipe 14. The liquid discharge of the evaporative condenser heat exchanger 12 is connected to a liquid reservoir 10 via an evaporative condenser liquid discharge pipe 6. The liquid reservoir 10 is connected to the suction of the compressor unit 1 via a liquid reservoir supply pipe 11, a throttle valve, an evaporator, and a gas-liquid separator (the throttle valve, evaporator, and gas-liquid separator are omitted in the accompanying drawings). This embodiment also includes a balancing pipe 9 for connecting the evaporative condenser heat exchanger 12 and the liquid reservoir 10. The upper end of the balancing pipe 9 is connected to the steam inlet of the evaporative condenser heat exchanger 12, and the lower end is connected to the liquid reservoir 10.

[0027] The high-temperature and high-pressure steam from the compressor unit 1 enters the evaporative condenser heat exchanger 12 through the compressor exhaust pipe 14. After condensation, part of the liquid phase is discharged into the liquid reservoir 10 through the evaporative condenser discharge pipe 6, and the other part enters the lubricating oil cooling subsystem to cool the lubricating oil.

[0028] This embodiment also includes a lubricating oil cooling subsystem, which includes an oil-cooled heat exchanger 2 connected to the oil inlet and outlet of the compressor unit 1 via a lubricating oil pipeline. The refrigerant inlet end of the oil-cooled heat exchanger 2 is connected to the evaporative condenser discharge pipe 6 via an oil-cooled refrigerant inlet pipe 3. The refrigerant outlet end of the oil-cooled heat exchanger 2 is connected to a horizontal gas-liquid separation pipe 5 via an oil-cooled refrigerant outlet pipe 4. The other end of the gas-liquid separation pipe 5 ( Figure 1 The right end of the liquid return pipe 7 and the gas return pipe 8 are connected respectively, wherein the other end of the liquid return pipe 7 ( Figure 1 The other end of the return pipe 8 ( Figure 1 The upper end of the return air pipe 8 is connected to the balance pipe 9, and the connection position between the return air pipe 8 and the balance pipe 9 is higher than the gas-liquid separation pipe 5. The connection position between the oil-cooled refrigerant inlet pipe 3 and the evaporative condenser discharge pipe 6 is lower than the gas-liquid separation pipe 5.

[0029] The high-temperature gas-liquid mixed phase refrigerant discharged from the oil-cooled heat exchanger 2 enters the horizontal gas-liquid separation tube 5, and gas-liquid separation is realized during the flow in the gas-liquid separation tube 5, wherein the liquid phase returns to the oil-cooled heat exchanger 2 or the liquid storage tank 10, and the gas phase returns to the evaporative condenser heat exchanger 12 under the suction action of the balance pipe 9.

[0030] Example 2

[0031] This embodiment relates to a large refrigeration system with two oil-cooled heat exchangers.

[0032] like Figure 2 The system of this embodiment includes two compressor units 1 and an evaporative condenser 13. The evaporative condenser 13 includes a housing and an evaporative condenser heat exchanger 12 installed in the housing. In this embodiment, the evaporative condenser 13 also includes a circulating fan and a circulating water pump. The evaporative condenser heat exchanger 12 dissipates heat by spraying water evaporation.

[0033] The steam inlet end of the evaporative condenser heat exchanger 12 is connected to the exhaust ends of the two compressor units 1 respectively through the compressor exhaust pipe 14. The liquid discharge end of the evaporative condenser heat exchanger 12 is connected to the liquid reservoir 10 through the evaporative condenser liquid discharge pipe 6. The liquid reservoir 10 is connected to the suction end of the compressor unit 1 through the liquid reservoir supply pipe 11, the throttle valve, the evaporator and the gas-liquid separator (the throttle valve, the evaporator and the gas-liquid separator are omitted in the accompanying drawings). This embodiment also includes a balancing pipe 9 for connecting the evaporative condenser heat exchanger 12 and the liquid reservoir 10. The evaporative condenser heat exchanger 12 in this embodiment has a two-stage heat exchanger, the upper end of the balancing pipe 9 is connected to the second-stage steam inlet manifold of the evaporative condenser heat exchanger 12, and the lower end is connected to the liquid reservoir 10.

[0034] The high-temperature and high-pressure steam from the two compressor units 1 enters the evaporative condenser heat exchanger 12 through the compressor exhaust pipe 14. After condensation, part of the liquid phase is discharged into the liquid reservoir 10 through the evaporative condenser discharge pipe 6, and the other part enters the lubricating oil cooling subsystem to cool the lubricating oil.

[0035] This embodiment also includes two lubricating oil cooling subsystems, one corresponding to each of the two compressor units 1. Each lubricating oil cooling subsystem includes an oil-cooling heat exchanger 2 connected to the oil inlet and outlet of the corresponding compressor unit 1 via a lubricating oil pipeline. This embodiment also includes a transition pipe 15. The refrigerant inlet end of each oil-cooling heat exchanger 2 is connected to the lower end of the transition pipe 15 via an oil-cooling refrigerant inlet pipe 3. The upper end of the transition pipe 15 is connected to the evaporative condenser drain pipe 6.

[0036] The refrigerant outlet end of the oil-cooled heat exchanger 2 is connected to a horizontal gas-liquid separation pipe 5 through an oil-cooled refrigerant outlet pipe 4. The other end of the gas-liquid separation pipe 5 ( Figure 2 The right end of the liquid return pipe 7 and the gas return pipe 8 are connected respectively, wherein the other end of the liquid return pipe 7 ( Figure 2 The other end of the return pipe 8 ( Figure 2The upper end of the oil cooling refrigerant inlet pipe 3 is connected to the balance pipe 9, and the connection position between the return air pipe 8 and the balance pipe 9 is higher than the gas-liquid separation pipe 5. The connection position between the oil cooling refrigerant inlet pipe 3 and the transition pipe 15 is lower than the gas-liquid separation pipe 5.

[0037] The high-temperature gas-liquid mixed phase refrigerant discharged from the oil-cooled heat exchanger 2 enters the horizontal gas-liquid separation tube 5, and gas-liquid separation is realized during the flow in the gas-liquid separation tube 5. Part of the liquid phase returns to the oil-cooled heat exchanger 2 through the evaporative condenser discharge pipe 6, and the rest enters the liquid reservoir 10. The gas phase returns to the evaporative condenser heat exchanger 12 under the suction action of the balance pipe 9.

[0038] Example 3

[0039] This embodiment relates to a large refrigeration system with two oil-cooled heat exchangers.

[0040] like Figure 3 The difference between this embodiment and the second embodiment is that the other end of the return pipe 7 ( Figure 3 The lower end) is directly connected to the oil-cooled refrigerant inlet pipe 3.

[0041] This embodiment is different from the second embodiment in that the oil-cooling refrigerant inlet pipe 3 is connected to an oil drain pipe 16 .

[0042] It should be noted that, although the two compressor units 1 in the drawings disclosed in this embodiment share an evaporative condenser 13 and a liquid reservoir 10, in fact, the two compressor units 1 can also be connected to an evaporative condenser and a liquid reservoir 10 respectively, or share an evaporative condenser 13 and be connected to a liquid reservoir 10 respectively, or share a liquid reservoir 10 and be connected to an evaporative condenser 13 respectively.

Claims

1. A lubricating oil cooling subsystem in a compressor refrigeration system, comprising a compressor unit (1) and an oil-cooled heat exchanger (2) connected to the compressor unit (1), further comprising a liquid reservoir (10) for connecting the liquid discharge end of an evaporative condenser heat exchanger (12) via an evaporative condenser liquid discharge pipe (6), and a balancing pipe (9) having an upper end for connecting to the evaporative condenser heat exchanger (12) and a lower end connected to the liquid reservoir (10), wherein the exhaust end of the compressor unit (1) is for connecting to the steam inlet end of the evaporative condenser heat exchanger (12), and the refrigerant inlet end of the oil-cooled heat exchanger (2) is for connecting to the evaporative condenser liquid discharge pipe (6) via an oil-cooled refrigerant inlet pipe (3), characterized in that: The refrigerant outlet end of the oil-cooled heat exchanger (2) is connected to a horizontally oriented gas-liquid separation tube (5) through an oil-cooled refrigerant outlet pipe (4); the other end of the gas-liquid separation tube (5) is respectively connected to a return liquid pipe (7) and a return air pipe (8); the other end of the return liquid pipe (7) is connected to the evaporative condenser discharge pipe (6) or the oil-cooled refrigerant inlet pipe (3), and the connection position between the return liquid pipe (7) and the evaporative condenser discharge pipe (6) is lower than the gas-liquid separation tube (5); the other end of the return air pipe (8) is connected to the balance pipe (9), and the connection position between the return air pipe (8) and the balance pipe (9) is higher than the gas-liquid separation tube (5); the connection position between the oil-cooled refrigerant inlet pipe (3) and the evaporative condenser discharge pipe (6) is lower than the gas-liquid separation tube (5).

2. The lubricating oil cooling subsystem in the compressor refrigeration system according to claim 1, characterized in that: The upper end of the balance pipe (9) is connected to the steam inlet end of the evaporative condenser heat exchanger (12).

3. The lubricating oil cooling subsystem in the compressor refrigeration system according to claim 1, characterized in that: The evaporative condenser heat exchanger (12) has more than two stages of heat exchangers; the upper end of the balance pipe (9) is connected to the middle steam inlet header of the evaporative condenser heat exchanger (12).

4. The lubricating oil cooling subsystem in the compressor refrigeration system according to claim 1, characterized in that: The subsystem further comprises a transition pipe (15); the upper end of the transition pipe (15) is connected to the evaporative condenser drain pipe (6); and the refrigerant inlet end of the oil-cooled heat exchanger (2) is connected to the lower end of the transition pipe (15) via the oil-cooled refrigerant inlet pipe (3).

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