Flooded water chiller system with return oil heat exchanger

Abstract

The utility model provides a flooded water chiller system with an oil return heat exchanger. The flooded water chiller system comprises a compressor, an oil separator, a condenser, the oil return heat exchanger, a flooded evaporator, a first switch device, a refrigerant circulation pipeline group and an oil return pipeline group. The oil return heat exchanger comprises a shell, a heat exchange pipeline, an oil return heat exchange inlet and an oil return heat exchange outlet, the heat exchange pipeline is arranged in the shell, the inlet end of the heat exchange pipeline is communicated with the oil return heat exchange inlet, and the outlet end of the heat exchange pipeline is communicated with the oil return heat exchange outlet. The main oil return loop comprises a first oil return pipeline and a second oil return pipeline in the oil return pipeline set, the first oil return pipeline is connected between a refrigerant leading-out opening of the flooded evaporator and an oil return heat exchange inlet of the oil return heat exchanger, and the second oil return pipeline is connected between an oil return heat exchange outlet of the oil return heat exchanger and the compressor.

Description

Technical Field

[0001] This utility model relates to a flooded chiller system with an oil return heat exchanger, and more particularly to a flooded chiller system with an oil return heat exchanger that can improve the ineffective work wasted by conventional flooded evaporators that use high-pressure gas as power for oil return. Background Technology

[0002] In traditional shell-and-tube or plate heat exchangers that use dry direct expansion, the refrigerant oil used for compressor cooling, lubrication, and oil sealing is discharged along with the high-temperature, high-pressure refrigerant gas and enters the refrigeration cycle system. The low-temperature refrigerant carrying the refrigerant oil exchanges heat with the ice water circulating on the shell side (inside the evaporative heat transfer copper tubes) and expands into a low-temperature, low-pressure refrigerant gas, which then returns to the compressor along with the refrigerant oil it contains.

[0003] Unlike chillers that use shell-and-tube or plate heat exchangers with dry direct expansion, modern chillers primarily employ flooded evaporators with pool boiling to achieve higher refrigeration energy efficiency. In the flooded evaporator, refrigerant containing refrigeration oil exchanges heat with the circulating chilled water on the tube side, boiling and evaporating into gaseous refrigerant. This gaseous refrigerant is drawn into the compressor. However, the refrigeration oil discharged from the compressor along with the high-temperature, high-pressure refrigerant, also evaporates and boils into oil bubbles. This oil cannot return to the compressor with the evaporated refrigerant gas and remains in the flooded evaporator. Over time, this leads to oil loss in the compressor, causing it to malfunction.

[0004] It is known that using a jet pump powered by high-pressure refrigerant gas to create an oil return device can solve the problem of refrigerant gas that cannot return to the compressor with the evaporated refrigerant gas and remains in the flooded evaporator. However, this jet pump oil return device using high-pressure refrigerant gas usually requires about 2-3% of the system refrigerant circulation volume of high-pressure refrigerant gas. That is, 2-3% of the refrigerant circulation volume of high-pressure refrigerant gas is directly bypassed from the compressor's discharge end to the compressor's suction end, which is equivalent to the compressor wasting ineffective work. Utility Model Content

[0005] The purpose of this invention is to provide a flooded chiller system with an oil return heat exchanger, which saves about 2-3% of the cooling capacity loss of conventional technology that uses a jet pump oil return device powered by high-pressure gas. This invention enables the flooded chiller system with an oil return heat exchanger to improve its cooling capacity and energy efficiency.

[0006] This utility model provides a flooded chiller system with a return oil heat exchanger, characterized in that it includes:

[0007] One compressor;

[0008] One oil separator;

[0009] A condenser;

[0010] An oil return heat exchanger includes a shell, a refrigerant heat exchange inlet, a refrigerant heat exchange outlet, a heat exchange pipeline, an oil return heat exchange inlet, and an oil return heat exchange outlet. The refrigerant heat exchange inlet and the refrigerant heat exchange outlet are provided at opposite ends of the shell, and the oil return heat exchange inlet and the oil return heat exchange outlet are provided on one side of the shell. The heat exchange pipeline is located inside the shell, with one inlet end of the heat exchange pipeline connected to the oil return heat exchange inlet and one outlet end of the heat exchange pipeline connected to the oil return heat exchange outlet.

[0011] A full-fill evaporator;

[0012] A first switching device; and

[0013] A refrigerant circulation pipeline assembly and an oil return pipeline assembly, wherein the refrigerant circulation pipeline assembly connects the compressor, the oil separator, the condenser, the oil return heat exchanger, the first switching device, and the flooded evaporator;

[0014] It also includes a main oil return circuit, which includes a first oil return pipeline and a second oil return pipeline in the oil return pipeline group; the first oil return pipeline is connected between a refrigerant outlet of the flooded evaporator and the oil return heat exchange inlet of the oil return heat exchanger, and the second oil return pipeline is connected between the oil return heat exchange outlet of the oil return heat exchanger and a suction inlet of the compressor.

[0015] The aforementioned flooded chiller system with an oil return heat exchanger further includes: an oil return injection pump, which forms a composite oil return device consisting of the oil return heat exchanger, the oil return injection pump, and the oil return pipeline assembly. The composite oil return device includes a main oil return circuit and an auxiliary oil return circuit. The auxiliary oil return circuit includes the oil return injection pump, the oil return heat exchanger, a third oil return pipeline, a fourth oil return pipeline, a fifth oil return pipeline, and the compressor. The third oil return pipeline is connected between the second oil return pipeline and the second inlet of the oil return injection pump of the oil return injection pump. The fourth oil return pipeline is connected between the first inlet of the oil return injection pump of the oil return injection pump and the exhaust outlet of the compressor. The fifth oil return pipeline is connected between the outlet of the oil return injection pump of the oil return injection pump and the intake inlet of the compressor.

[0016] The full-fill chiller system with a return oil heat exchanger, wherein: the first return oil pipeline and the fourth return oil pipeline are each equipped with at least one switching device.

[0017] The full-fill chiller system with a return oil heat exchanger, wherein: the at least one switching device is an electronic expansion valve or a solenoid valve.

[0018] The flooded chiller system with a return oil heat exchanger further includes:

[0019] An oil separator return circuit includes at least one switching device, an oil level detector, and a sixth return oil line in the return oil line group, wherein the oil level detector is located on the compressor, the sixth return oil line connects an oil return inlet of the compressor to an oil return outlet of the oil separator, and the at least one switching device is located on the sixth return oil line.

[0020] The full-fill chiller system with a return oil heat exchanger, wherein: the at least one switching device is an electronic expansion valve or a solenoid valve.

[0021] Based on the above, the flooded chiller system with oil return heat exchanger of this invention, when the compressor is running, guides the oil-rich refrigerant liquid from the flooded evaporator into the pipe-side circuit within the oil return heat exchanger. There, it exchanges heat with the high-pressure, high-temperature refrigerant liquid from the condenser. The low-pressure, oil-rich refrigerant liquid on the pipe side gains heat from the high-pressure, high-temperature refrigerant liquid, causing the refrigerant to evaporate into gas. The 5% refrigerant oil in the refrigerant liquid generates lift due to the boiling oil bubbles caused by the refrigerant evaporation, and is drawn from the pipe-side outlet into the compressor's suction inlet, achieving a non-powered oil return effect (eliminating the need for high-pressure gas). Under the same compressor suction mass flow rate, the flooded chiller system with oil return heat exchanger of this invention, compared to conventional technology, has an increased enthalpy difference, thus increasing the refrigeration effect and improving the cooling capacity.

[0022] To make this utility model more apparent and understandable, embodiments are listed below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a full-fill chiller system with an oil return heat exchanger according to the present invention.

[0024] Figure 2 This is a schematic diagram of the oil return heat exchanger of this utility model.

[0025] Figure 3 for Figure 2 A schematic diagram of one side of the return oil heat exchanger.

[0026] Figure 4 This is a schematic diagram showing the pressure and enthalpy of a chiller system that uses a jet pump return device.

[0027] Figure 5This is a schematic diagram showing the pressure and enthalpy of the full-fill chiller system with a return oil heat exchanger according to this utility model.

[0028] Explanation of reference numerals in the attached diagram: 1g - Saturation point; 4f, 10, 20, 30, 301, 40, 401 - State points; 100 - Flooded chiller system with oil return heat exchanger; 11 - Compressor; 112 - Inlet; 114 - Outlet; 116 - Oil return inlet; 118 - Oil level detector; 21 - Oil separator; 212 - Oil separator inlet; 214 - Oil separator outlet; 216 - Oil return outlet; 31 - Condenser; 312 - Condenser inlet; 314 - Condenser outlet; 41 - Oil return heat exchanger; 411 - Shell; 412 - Refrigerant heat exchange inlet; 414 - Refrigerant heat exchange outlet; 415 - Heat exchange piping; 416 - Oil return heat exchange inlet; 418 - Oil return heat exchange outlet; 51 - Flooded evaporator; 512 - Evaporator outlet; 514 - Evaporator inlet; 516 - Refrigerant outlet; 61 - Oil return jet pump; 612 - First inlet of oil return jet pump; 614 - Second inlet of oil return jet pump; 616 - Return oil injection pump outlet; B1-Inlet end; B2-Outlet end; G1-Chill water inlet; G2-Chill water outlet; he1, he2-Enthalpy difference; L-Length direction; PA-Refrigerant circulation pipeline group; P1-First refrigerant pipeline; P2-Second refrigerant pipeline; P3-Third refrigerant pipeline; P4-Fourth refrigerant pipeline; P5-Fifth refrigerant pipeline; P6-Sixth refrigerant pipeline; P61-First inlet; P62-Second inlet; RA-Return oil pipeline group; R1-First return oil pipeline; R2 - Second return oil line; R3 - Third return oil line; R4 - Fourth return oil line; R5 - Fifth return oil line; R6 - Sixth return oil line; RD - Composite return oil device; RDA - Main return oil circuit; RDB - Auxiliary return oil circuit; RDC - Oil separator return oil circuit; RL - Red dashed line; V1 - First switch device; V12 - First switch inlet; V14 - First switch outlet; V2 - Second switch device; V3 - Third switch device; V4 - Fourth switch device. Detailed Implementation

[0029] The following description provides detailed examples and accompanying drawings, but these examples are not intended to limit the scope of the present invention. Furthermore, the drawings are for illustrative purposes only and are not drawn to their original dimensions. For ease of understanding, the same elements will be designated with the same symbols in the following description.

[0030] The terms "including", "comprise", "have" and other similar terms used in this utility model are all open-ended, meaning "including but not limited to".

[0031] In the description of the various embodiments, when the terms "first," "second," "third," "fourth," etc. are used to describe elements, they are only used to distinguish these elements from each other and do not limit the order or importance of these elements.

[0032] In the description of the various embodiments, the term "coupled" or "connected" may refer to two or more elements making direct physical or electrical contact with each other, or making indirect physical or electrical contact with each other. "Coupled" or "connected" may also refer to two or more elements operating or moving with each other.

[0033] In the description of the various embodiments, the term "module" refers to a hardware module, that is, a hardware component that occupies space. In other embodiments, the term "module" may also refer to a hardware module plus a software module, that is, a "module" has software programs in addition to hardware components.

[0034] Figure 1 This is a schematic diagram of a flooded chiller system with a return oil heat exchanger according to the present invention. Please refer to [link / reference]. Figure 1 The flooded chiller system 100 of this utility model with an oil return heat exchanger includes at least a compressor 11, an oil separator 21, a condenser 31, an oil return heat exchanger 41, a flooded evaporator 51, an oil return ejector 61, and at least one switching device (such as...). Figure 1 The diagram shows a first switching device V1, a second switching device V2, a third switching device V3, a fourth switching device V4, a refrigerant circulation pipeline group PA, and an oil return pipeline group RA. The first switching device V1, the second switching device V2, the third switching device V3, and the fourth switching device V4 can be an electronic expansion valve, a solenoid valve, or other components that can perform pipeline switching. The copper tubes of the flooded evaporator 51 are completely immersed in the refrigerant and provide a chilled water inlet G1 and a chilled water outlet G2. The chilled water of the chiller forms a circulating chilled water system from the chilled water inlet G1 to the chilled water outlet G2.

[0035] The refrigerant circulation piping group PA consists of the first refrigerant piping P1, the second refrigerant piping P2, the third refrigerant piping P3, the fourth refrigerant piping P4, the fifth refrigerant piping P5, and the sixth refrigerant piping P6. The oil return piping group RA consists of the first oil return piping R1, the second oil return piping R2, the third oil return piping R3, the fourth oil return piping R4, the fifth oil return piping R5, and the sixth oil return piping R6. To distinguish between the refrigerant circulation piping group PA and the oil return piping group RA, the first refrigerant piping P1, the second refrigerant piping P2, the third refrigerant piping P3, the fourth refrigerant piping P4, the fifth refrigerant piping P5, and the sixth refrigerant piping P6 are represented by dashed lines, while the first oil return piping R1, the second oil return piping R2, the third oil return piping R3, the fourth oil return piping R4, the fifth oil return piping R5, and the sixth oil return piping R6 are represented by solid lines.

[0036] The flooded chiller system 100 with an oil return heat exchanger has a main refrigerant circulation, wherein: the compressor 11 is provided with an intake inlet 112 and an exhaust outlet 114; the oil separator 21 is provided with an oil separator inlet 212 and an oil separator outlet 214; the condenser 31 is provided with a condenser inlet 312 and a condenser outlet 314; the oil return heat exchanger 41 is provided with a refrigerant heat exchange inlet 412, a refrigerant heat exchange outlet 414, and an oil return heat exchange inlet 416; the first switching device V1 is provided with a first switching inlet V12 and a first switching outlet V14; and the flooded evaporator 51 is provided with an evaporator outlet 512 and an evaporator inlet 514.

[0037] The first refrigerant line P1 connects the discharge outlet 114 of the compressor 11 to the oil separator inlet 212 of the oil separator 21. The second refrigerant line P2 connects the oil separator outlet 214 of the oil separator 21 to the condenser inlet 312 of the condenser 31. The third refrigerant line P3 connects the condenser outlet 314 of the condenser 31 to the refrigerant heat exchange inlet 412 of the oil return heat exchanger 41. The fourth refrigerant line P4 connects the refrigerant heat exchange outlet 414 of the oil return heat exchanger 41 to the first switch inlet V12 of the first switching device V1. The fifth refrigerant line P5 connects the first switch outlet V14 of the first switching device V1 to the evaporator inlet 514 of the flooded evaporator 51. The sixth refrigerant line P6 connects the evaporator outlet 512 of the flooded evaporator 51 to the suction inlet 112 of the compressor 11. This utility model uses a refrigerant circulation pipeline PA consisting of a first refrigerant pipeline P1, a second refrigerant pipeline P2, a third refrigerant pipeline P3, a fourth refrigerant pipeline P4, a fifth refrigerant pipeline P5, and a sixth refrigerant pipeline P6 to connect a compressor 11, an oil separator 21, a condenser 31, an oil return heat exchanger 41, a first switching device V1, and a flooded evaporator 51, to form the main refrigerant circulation of a flooded chiller system 100 with an oil return heat exchanger.

[0038] The refrigerant circulation process proceeds sequentially as follows: refrigerant heat absorption (evaporation), compression, condensation, and oil return. The flooded evaporator 51 is a type of evaporator used in refrigeration or in a flooded chiller system 100 with an oil return heat exchanger. Refrigerant heat absorption occurs when liquid refrigerant absorbs heat from the circulating chilled water (chilled water inlet G1, chilled water outlet G2) in the flooded evaporator 51 and transforms into gaseous refrigerant. The liquid refrigerant circulates through the pipes of the flooded evaporator 51 and gradually evaporates into gaseous refrigerant. During this process, the refrigerant gradually transforms from liquid to gas, while simultaneously absorbing heat from the circulating chilled water from the chilled water inlet G1 to the chilled water outlet G2. The flooded evaporator 51 provides more efficient heat exchange, maintains the refrigerant's saturation state, and maximizes heat exchange efficiency. Next, the gaseous refrigerant enters the compressor 11, where it is compressed into a high-temperature, high-pressure gas. In a flooded chiller system 100 with an oil return heat exchanger, compressor 11 functions by compressing low-pressure, low-temperature refrigerant vapor into high-pressure, high-temperature refrigerant gas. Compressor 11 draws in refrigerant vapor from the evaporator, pressurizes it, and delivers it to condenser 31, where the temperature and pressure of the compressed refrigerant gas significantly increase. Since the lubricating oil used in compressor 11 is mixed with the refrigerant, oil separator 21 separates the oil from the refrigerant, reducing the amount of oil entering the subsequent condenser 31. Next, the high-temperature, high-pressure gaseous refrigerant enters condenser 31, releases heat, and cools into liquid refrigerant. The refrigerant, after compression, becomes a high-temperature, high-pressure gas and enters condenser 31. The function of condenser 31 is to cool the refrigerant gas, causing it to lose heat and transform into liquid refrigerant. Condenser 31 typically absorbs heat through water or air, condensing the refrigerant gas into high-pressure liquid refrigerant. Next, the liquid refrigerant passes through the condenser 31 and the oil return heat exchanger 41, and then re-enters the flooded evaporator 51 to continue absorbing heat and re-evaporating, forming a closed refrigerant cycle. This refrigerant cycle system is the core working principle of the flooded chiller system 100 with an oil return heat exchanger. Through processes such as compression, condensation, and evaporation, the flooded chiller system 100 with an oil return heat exchanger ensures efficient cooling.

[0039] In addition, the flooded chiller system 100 with an oil return heat exchanger also has a composite oil return device RD consisting of an oil return heat exchanger 41, an oil return pipeline assembly RA, and an oil return jet pump 61, wherein: the oil return jet pump 61 has a first oil return jet pump inlet 612, a second oil return jet pump inlet 614, and an oil return jet pump outlet 616; the flooded evaporator 51 also includes a refrigerant outlet 516, the position of which is different from the positions of the evaporator outlet 512 and the evaporator inlet 514; the oil return heat exchanger 41 also includes an oil return heat exchange inlet 416. A return oil heat exchange outlet 418 is provided; a sixth refrigerant line P6 is connected between the suction inlet 112 of the compressor 11 and a first inlet P61 and a second inlet P62 are respectively provided; the compressor 11 also includes an oil return inlet 116 and an oil level detector 118. The position of the oil return inlet 116 is different from that of the suction inlet 112 and the exhaust outlet 114. The oil level detector 118 is located at the position of the oil return inlet 116; the oil separator 21 also includes an oil return outlet 216. The position of the oil return outlet 216 is different from that of the oil separator inlet 212 and the oil separator outlet 214.

[0040] The first return oil line R1 connects the refrigerant outlet 516 of the flooded evaporator 51 to the return oil heat exchange inlet 416 of the return oil heat exchanger 41. The second return oil line R2 connects the return oil heat exchange outlet 418 of the return oil heat exchanger 41 to the first inlet P61 of the sixth refrigerant line P6. The third return oil line R3 connects the second return oil line R2 to the second inlet 614 of the return oil injection pump 61. The fourth return oil line R4 connects to the return oil injection pump. The first inlet 612 of the return oil injection pump of 61 is between the second refrigerant line P2, and the third switch device V3 is located in the fourth return oil line R4. The fifth return oil line R5 is connected between the return oil injection pump outlet 616 of the return oil injection pump 61 and the second inlet P62 of the sixth refrigerant line P6. The sixth return oil line R6 is connected between the return oil inlet 116 of the compressor 11 and the return oil outlet 216 of the oil separator 21. The sixth return oil line R6 is different from the first refrigerant line P1.

[0041] The aforementioned oil return device RD is a composite oil return system 100 with an oil separator 21, a condenser 31, an oil return heat exchanger 41, and a flooded evaporator 51, which are connected to the oil return pipeline group RA consisting of the oil return injection pump 61, the first oil return pipeline R1, the second oil return pipeline R2, the third oil return pipeline R3, the fourth oil return pipeline R4, the fifth oil return pipeline R5, and the sixth oil return pipeline R6.

[0042] Figure 2 This is a schematic diagram of the oil return heat exchanger of this utility model. Figure 3 for Figure 2 A schematic diagram of one side of the oil return heat exchanger. Please refer to [link / reference]. Figure 2 and Figure 3 The oil return heat exchanger 41 of this utility model includes a shell 411, a refrigerant heat exchange inlet 412, a refrigerant heat exchange outlet 414, a heat exchange pipeline 415, an oil return heat exchange inlet 416, and an oil return heat exchange outlet 418. The shell 411 has refrigerant heat exchange inlets 412 and refrigerant heat exchange outlets 414 at opposite ends along the length direction L. A third refrigerant pipeline P3 is provided between the inlet of the shell 411 of the oil return heat exchanger 41 (i.e., the refrigerant heat exchange inlet 412) and the condenser outlet 314 of the condenser 31. A fourth refrigerant pipeline P4 is provided between the outlet of the shell 411 of the oil return heat exchanger 41 (the refrigerant heat exchange outlet 414) and the first switch inlet V12 of the first switch device V1. Here, the third refrigerant pipeline P3 and the fourth refrigerant pipeline P4 are respectively high-pressure liquid refrigerant connection pipelines.

[0043] The shell side of the casing 411 is provided with an oil return heat exchange inlet 416 and an oil return heat exchange outlet 418. A heat exchange pipeline 415 is located inside the casing 411 and is a shell-ring type heat exchanger, serving as an oil return or subcooler. In this way, refrigerant enters the casing 411 through the oil return heat exchange inlet 416, undergoes heat exchange through the heat exchange pipeline 415, and the refrigerant after heat exchange flows out through the refrigerant heat exchange outlet 414. Furthermore, the inlet end B1 of the heat exchange pipeline 415 is connected to the oil return heat exchange inlet 416, and the outlet end B2 of the heat exchange pipeline 415 is connected to the oil return heat exchange outlet 418, forming an oil return circulation path.

[0044] Please refer to the following: Figure 1 , Figure 2 and Figure 3 The composite oil return device RD of this utility model is configured with a main oil return circuit RDA, an auxiliary oil return circuit RDB, and an oil separator oil return circuit RDC by means of an oil return heat exchanger 41, an oil return pipeline group RA, and an oil return jet pump 61. The main oil return circuit RDA performs a non-powered oil return step for a long time. The auxiliary oil return circuit RDB assists the main oil return circuit RDA under specific conditions so that oil can be returned from the flooded evaporator 51 to the compressor 11. The specific conditions are such as insufficient oil bubble lift when the compressor 11 is operating under partial load.

[0045] The main oil return circuit RDA includes a flooded evaporator 51, a first oil return line R1, an oil return heat exchanger 41, a second oil return line R2, and a compressor 11.

[0046] A first oil return line R1 is provided between the oil return heat exchanger 41 and the flooded evaporator 51, so that the refrigerant outlet 516 of the flooded evaporator 51 serves as an oil return guide outlet. In one embodiment, the first oil return line R1 connects the refrigerant outlet 516 of the flooded evaporator 51 and the oil return heat exchange inlet 416 of the oil return heat exchanger 41, and the first oil return line R1 may be equipped with a second switching device V2 as a switch to open or close the refrigerant outlet 516. The second switching device V2 is, for example, a solenoid valve.

[0047] At least one return oil line is connected between the return oil heat exchange outlet 418 of the return oil heat exchanger 41 and the suction inlet 112 of the compressor 11. For example, the second return oil line R2 connects the return oil heat exchange outlet 418 of the return oil heat exchanger 41 and the first inlet P61 of the sixth refrigerant line P6. The first inlet P61 of the sixth refrigerant line P6 is connected to the suction inlet 112 of the compressor 11, so that the return oil heat exchanger 41 can be connected to the compressor 11 through the second return oil line R2.

[0048] In this way, the oil-rich refrigerant liquid in the flooded evaporator 51 is transported from the refrigerant outlet 516 to the heat exchange pipeline 415 inside the oil return heat exchanger 41 via the first oil return pipeline R1 and the oil return heat exchanger 41's oil return heat exchanger 41. At this time, the high-pressure, high-temperature liquid refrigerant in the condenser 31 is transferred to the interior of the shell inlet (i.e., refrigerant heat exchange inlet 412) of the oil return heat exchanger 41 via the third refrigerant pipeline P3, so that the high-pressure, high-temperature liquid refrigerant can exchange heat with the oil-rich refrigerant liquid located in the heat exchange pipeline 415. The low-pressure oil-rich refrigerant liquid in the heat exchange pipeline 415 evaporates into gas due to the heat obtained from the high-pressure, high-temperature refrigerant liquid. 5% of the refrigeration oil in the oil-rich refrigerant liquid generates lift due to the boiling oil bubbles caused by the evaporation of the refrigerant. The refrigeration oil generating lift is led out through the oil return heat exchange outlet 418 of the oil return heat exchanger 41 to the second oil return pipeline R2, and enters the suction inlet 112 of the compressor 11 through the second oil return pipeline R2, achieving the effect of unpowered oil return (eliminating the need for high-pressure gas). This process allows the oil bubbles from the evaporator 51, rich in oil, to return oil to the compressor 11 due to their lift effect, and also causes subcooling of the high-pressure, high-temperature liquid, thereby increasing the cooling effect of the evaporator 51 and improving the cooling energy efficiency of the compressor 11. In one embodiment, the second oil return line R2 is connected to the compressor 11 through the first inlet P61 of the sixth refrigerant line P6.

[0049] The auxiliary return oil circuit RDB includes a return oil injection pump 61, a return oil heat exchanger 41, a third return oil line R3, a fourth return oil line R4, a fifth return oil line R5, and a compressor 11.

[0050] A third return oil line R3 is provided between the second inlet 614 of the return oil injection pump 61 and the second return oil line R2. The third return oil line R3 connects the second return oil line R2 and the second inlet 614 of the return oil injection pump 61. The second return oil line R2 serves as the connecting line of the main return oil circuit RDA. The auxiliary return oil circuit RDB is connected to the main return oil circuit RDA through the third return oil line R3.

[0051] The oil return injection pump 61's first inlet 612 and the compressor 11's exhaust outlet 114's connecting pipe (first refrigerant pipe P1 and second refrigerant pipe P2) are connected to at least one oil return pipe, so as to... Figure 1 For example, the fourth return oil line R4 is connected between the first inlet 612 of the return oil injection pump 61 and the second refrigerant line P2, and the third switch device V3 is located in the fourth return oil line R4. The third switch device V3 is, for example, a solenoid valve.

[0052] At least one return oil line is connected between the return oil injection pump outlet 616 of the return oil injection pump 61 and the connecting line (sixth refrigerant line P6) between the suction inlet 112 of the compressor 11, so as to... Figure 1 For example, the fifth return oil line R5 connects the return oil injection pump outlet 616 of the return oil injection pump 61 to the second inlet P62 of the sixth refrigerant line P6.

[0053] In this configuration, the auxiliary oil return circuit RDB is used to assist the main oil return circuit RDA when the oil bubble lift effect is insufficient during partial load operation of the compressor 11. It activates the third switch V3 on the fourth oil return line R4 in the auxiliary oil return circuit RDB. At this time, the slightly reduced high-pressure refrigerant gas serves as the power source for the oil return injection pump 61, driving it to draw incompletely evaporated oil-rich refrigerant liquid from the oil return heat exchanger 41 through the oil return heat exchange outlet 418, the second oil return line R2, and the third oil return line R3. The high-pressure refrigerant air evaporates the oil-rich refrigerant liquid, which then returns to the compressor 11 via the second inlet P62 of the fifth oil return line R5 and the suction inlet 112 of the compressor 11. Since the compressor 11 operates under partial load, the loss of cooling capacity and the impact on cooling energy efficiency are relatively small. Assisted oil return to the compressor 11 is achieved by using high-pressure gas to drive the oil return jet pump 61, which draws the refrigerant oil from the oil return outlet (i.e., the oil return heat exchange outlet 418) on the tube side of the oil return heat exchanger 41 back to the compressor 11. Therefore, the composite oil return device RD of this invention can selectively activate the oil return jet pump 61 to assist oil return via the fifth oil return line R5, depending on the oil return situation. This reduces the loss of cooling capacity and ineffective power in conventional systems that rely entirely on high-pressure gas.

[0054] The oil separator return circuit RDC includes a compressor 11, an oil separator 21, and a sixth oil return line R6. The compressor 11 has an oil level detector 118 and at least one oil return inlet (such as oil return inlet 116). The sixth oil return line R6 connects the oil return inlet 116 of the compressor 11 to the oil return outlet 216 of the oil separator 21. A fourth switch device V4 is installed on the sixth oil return line R6. The oil level detector 118 of the compressor 11 is used to control the fourth switch device V4 on the sixth oil return line R6, so that the refrigerant oil in the oil separator 21 returns to the compressor 11. This prevents the refrigerant oil that is not intercepted by the oil separator 21 from accumulating in the flooded evaporator 51 with the discharge of the compressor 11. This reduces or prevents the oil concentration in the flooded evaporator 51 from increasing, prevents the evaporation temperature from deteriorating, and prevents the oil bubbles from gradually increasing during refrigerant boiling, which could lead to liquid compression of the compressor 11, thus preventing the compressor 11 from losing oil.

[0055] Figure 4 This diagram illustrates the pressure and enthalpy of a conventional chiller system using a jet pump oil return device. The pressure and enthalpy changes caused by the compression, condensation, and evaporation processes are represented by state points 10, 20, 30, and 40. The conventional oil return device, powered by high-pressure refrigerant gas, utilizes the high-pressure refrigerant gas from the oil separator outlet. A jet pump draws a mixture of refrigerant and oil from the high-oil-concentration opening of the flooded evaporator. This mixture then passes through the condenser and exchanges heat with the high-temperature liquid refrigerant, increasing the subcooling of the high-pressure liquid refrigerant and causing the high-concentration oil-containing refrigerant to evaporate. The mixture can then selectively pass through the oil separator again for heat exchange with high-temperature refrigeration oil. After sufficient evaporation, the refrigerant returns to the compressor via the compressor suction pipe.

[0056] Jet pumps use high-pressure gas as power, that is, from Figure 4 At state point 20 in the pressure and enthalpy diagram, 2-3% of the high-pressure gas bypasses and enters the ejector pump, drawing the oil-rich refrigerant liquid from the flooded evaporator into the ejector pump. The two fluids mix and are discharged from the ejector pump outlet, then return to the compressor via the compressor suction pipe, thus performing oil return to the compressor. Generally, after the refrigerant discharged from the compressor passes through an oil separator to separate the refrigerant oil, approximately 0.1% (wt) of refrigerant gas mass flow rate of refrigerant oil will still enter the condenser. This means that 0.1% of the refrigerant mass flow rate of refrigerant oil is lost from the compressor and enters the system, accumulating in the flooded evaporator. Based on empirical sampling, the oil concentration in the flooded evaporator is approximately 5%. Since the refrigerant oil discharged from the compressor is 0.1%, the mass of refrigerant oil drawn from the flooded evaporator must also be 0.1% of the refrigerant gas mass flow rate discharged from the compressor. This ensures that the compressor's refrigerant oil is balanced and there is no risk of oil loss.

[0057] Since the refrigerant oil concentration in a flooded evaporator is 5%, a 2% refrigerant mass flow rate of oil with a 5% rich oil refrigerant concentration needs to be drawn from the flooded evaporator to recover the 0.1% refrigerant oil lost by the compressor. The jet pump has a gas-liquid ratio of 1:1, meaning that 1 part high-pressure gas plus 1 part rich oil refrigerant liquid, equivalent to 4% of the total refrigerant mass flow rate, is needed to balance the oil discharged and returned by the compressor. Figure 4 The red dashed line RL at state point 20 represents the high-pressure gas extracted, which mixes with the oil-rich refrigerant liquid extracted from the evaporator at state point 4f, and then mixes with the saturated state point 1g to reach state point 10 before entering the compressor. The 2% hot gas exiting the compressor and the 2% oil-rich refrigerant liquid exiting the flooded evaporator bypass the compressor without undergoing any cooling process. This means that the compressor loses up to 4% of its cooling capacity by using the jet pump to return oil.

[0058] Conventional technologies utilize jet pump oil return devices powered by high-pressure refrigerant gas. Typically, this requires approximately 2-3% of the system's refrigerant circulation volume to be supplied with high-pressure refrigerant gas. This means that 2-3% of the refrigerant circulation volume is directly bypassed from the compressor's discharge end to its suction end, which is equivalent to wasting the compressor's power.

[0059] The following describes the control method of the composite oil return device in the flooded chiller system 100 with oil return heat exchanger of this invention, so as to execute the main oil return circuit RDA, the auxiliary oil return circuit RDB, and the oil separator oil return circuit RDC, so that the flooded chiller system 100 with oil return heat exchanger of this invention can save about 2-3% of the cooling capacity loss of conventional technology using high-pressure gas-powered jet pump oil return device technology.

[0060] First, the oil return process from the flooded evaporator 51 to the compressor 11 is controlled by performing a non-powered oil return process using the main oil return circuit RDA, which remains open for an extended period. Oil-rich refrigerant from the flooded evaporator 51 is transported to the oil return heat exchanger 41 via the first oil return line R1. The refrigerant outlet 516 of the flooded evaporator 51 serves as an oil return guide outlet. The oil-rich refrigerant from the flooded evaporator 51 flows from the refrigerant outlet 516 through the first oil return line R1 and the oil return heat exchange inlet 416 of the oil return heat exchanger 41, and is then transported to the heat exchange line 415 inside the oil return heat exchanger 41. At this time, the high-pressure, high-temperature liquid refrigerant in the condenser 31 is transferred to the interior of the shell inlet (i.e., refrigerant heat exchange inlet 412) of the oil return heat exchanger 41 via the third refrigerant pipeline P3, so that the high-pressure, high-temperature liquid refrigerant can exchange heat with the oil-rich refrigerant liquid located in the heat exchange pipeline 415; after the heat exchange, a refrigeration oil in the oil-rich refrigerant liquid can be led out to a second oil return pipeline R2 via the oil return heat exchange outlet 418 of the oil return heat exchanger 41. The low-pressure oil-rich refrigerant liquid in the heat exchange pipeline 415 evaporates into gas due to the heat from the high-pressure, high-temperature refrigerant liquid. 5% of the refrigeration oil in the oil-rich refrigerant liquid generates lift due to the boiling oil bubbles caused by the refrigerant evaporation. The refrigeration oil generating lift is led out to the second oil return pipeline R2 via the oil return heat exchange outlet 418 of the oil return heat exchanger 41. Next, the refrigerant oil is introduced into the suction inlet 112 of the compressor 11 via the second oil return line R2, achieving a non-powered oil return effect (eliminating the need for high-pressure gas). This process allows the oil bubbles from the oil-rich refrigerant liquid in the flooded evaporator 51 to return oil to the compressor 11 due to their lift effect, and also generates subcooling in the high-pressure, high-temperature liquid state, thereby increasing the cooling effect of the flooded evaporator 51 and improving the cooling energy efficiency of the compressor 11. In one embodiment, the second oil return line R2 is connected to the compressor 11 via the first inlet P61 of the sixth refrigerant line P6.

[0061] Therefore, the composite oil return device RD of this invention can be applied to the flooded chiller system 100 with an oil return heat exchanger. The oil-rich refrigerant liquid is drawn from the flooded evaporator 51 and returned to the compressor 11 without power. This saves about 2-3% of the cooling capacity loss of the traditional jet pump oil return device technology that uses high-pressure gas as power, thereby improving the cooling capacity and energy efficiency of the flooded chiller system 100 with an oil return heat exchanger.

[0062] Compared to Figure 4 The commonly used technology, Figure 5 This is a schematic diagram illustrating the pressure and enthalpy of the flooded chiller system with a return oil heat exchanger according to this invention. Please refer to [link / reference]. Figure 5 , Figures 1 to 3When the compressor 11 operates under high load conditions, the oil-rich refrigerant liquid in the flooded evaporator 51 is guided into the pipe-side circuit (i.e., heat exchange pipe 415) within the oil return heat exchanger 41, where it exchanges heat with the high-pressure, high-temperature refrigerant liquid from the condenser 31. The low-pressure oil-rich refrigerant liquid on the pipe side (i.e., heat exchange pipe 415) gains heat from the high-pressure, high-temperature refrigerant liquid, causing the refrigerant to evaporate into gas. The 5% of the refrigerant oil in the liquid is lifted by the boiling oil bubbles caused by the refrigerant evaporation, and exits from the pipe-side outlet (i.e., the oil return heat exchange outlet 418 of the oil return heat exchanger 41) into the suction inlet 112 of the compressor 11, achieving a non-powered oil return effect (eliminating the need for high-pressure gas). Meanwhile, the high-pressure, high-temperature refrigerant liquid from the condenser 31 outlet enters from the shell-side inlet of the oil return heat exchanger 41 (i.e., refrigerant heat exchange inlet 412), exchanging heat with the low-pressure oil-rich refrigerant liquid evaporating on the pipe side (i.e., heat exchange pipe 415), and exits from... Figure 5 The state point changes from 30 to 301, resulting in subcooling. After depressurization and expansion through the expansion valve, it reaches state point 401. Compared to the original state point 30 without a return oil heat exchanger, the depressurization and expansion to state point 40 increases the refrigeration effect within the flooded evaporator 51. Figure 4 The enthalpy difference he1 is Δhe = h10 - h40, and the enthalpy difference he2 of this invention is Δhe = h10 - h401. That is, Δhe = h10 - h40 becomes Δhe = h10 - h401, and the enthalpy difference increases to h40 - h401. Under the same suction mass flow rate of compressor 11, this invention, compared to... Figure 4 The conventional technology increases the enthalpy difference, thus increasing the freezing effect and improving the refrigeration capacity. This further verifies the effectiveness of this invention in improving the refrigeration capacity and energy efficiency of the flooded chiller system 100 with an oil return heat exchanger. The aforementioned high-load conditions include, for example, when the compressor 11 needs to handle a greater workload or demand than usual during operation, such as increased flow rate or the compressor needing to operate at higher pressures. These high-load conditions can be interpreted according to actual circumstances.

[0063] In one embodiment, when the compressor 11 is operating under partial load conditions, an auxiliary oil return circuit RDB performs a power oil return step to assist the main oil return circuit RDA in returning oil from the flooded evaporator 51 to the compressor 11, wherein the auxiliary oil return circuit RDB is connected to the main oil return circuit RDA via a third oil return line R3.

[0064] The compressor 11 can be operated under partial load conditions as follows: the compressor 11 is partially loaded at a rate of less than or equal to 50%, where the calculation is based on 1 / 2 of the compressor 11's full-load rated current.

[0065] In other embodiments, when the compressor 11 operates under partial load conditions, the following detection information can be used to determine the operation: detecting the refrigerant-side pressure and the chilled water outlet temperature of the flooded evaporator 51, wherein the refrigerant-side pressure can be measured by a pressure gauge installed at the evaporator outlet 512, and the chilled water outlet temperature can be measured by a temperature gauge installed at the chilled water outlet G2. Next, based on the refrigerant type, a saturated refrigerant temperature corresponding to an evaporation pressure is calculated; a temperature difference between the saturated refrigerant temperature corresponding to the evaporation pressure and the chilled water outlet temperature is calculated to obtain an evaporator progressive temperature difference; and the calculated evaporator progressive temperature difference value is compared with an evaporator progressive temperature difference setpoint. When the evaporator progressive temperature difference value is greater than or equal to the evaporator progressive temperature difference setpoint, the oil return circuit RDB is assisted in performing the power oil return step.

[0066] Therefore, when the compressor 11 operates under partial load conditions, the temperature difference between the high-pressure refrigerant liquid in the condenser 31 and the low-pressure rich oil refrigerant liquid drawn by the self-filling evaporator 51 decreases. Consequently, the low-pressure rich oil refrigerant liquid may not evaporate completely, resulting in insufficient lift from the oil bubbles. At this time, a slightly reduced high-pressure gas is used as the power source for the return oil injection pump 61, drawing in the incompletely evaporated rich oil refrigerant liquid for evaporation and passing it through the suction pipe (towards...). Figure 1 For example, the sixth refrigerant line P6 is connected to the suction inlet 112 of the compressor 11 via the path of the refrigerant line P6 returning oil to the compressor 11. Because it operates under partial load conditions, the loss of cooling capacity and the impact on cooling energy efficiency are relatively small.

[0067] In addition, this utility model can also control the oil return process from the oil separator 21 to the compressor 11 by using an oil separator return circuit RDC: the compressor 11 is detected by an oil level detector 118. When the compressor 11 is in a low oil level state, at least one switching device (such as the fourth switching device V4) located on a sixth oil return line R6 is turned on, so that the refrigerant oil separated in the oil separator 21 is transported to the compressor 11 through the sixth oil return line R6 from the oil return inlet 116 of the compressor 11. This prevents the refrigerant oil that is not intercepted by the oil separator 21 from accumulating in the flooded evaporator 51 with the discharge of the compressor 11, thereby reducing or preventing the oil concentration in the flooded evaporator 51 from increasing, preventing the evaporation temperature from deteriorating, and preventing the oil bubbles from gradually increasing during refrigerant boiling, which would lead to compressor 11 fluid compression, thus preventing the compressor 11 from losing oil. When the compressor 11 is in a high oil level state, at least one switching device (such as the fourth switching device V4) located on the sixth oil return line R6 is turned off, so as to stop the oil separator 21 from returning oil to the compressor 11 through the sixth oil return line R6.

[0068] In addition, in one embodiment, this utility model can control the oil return when the compressor 11 experiences hydraulic compression oil loss. The control steps are as follows: Detect the refrigerant discharge pressure (discharge pressure) and discharge temperature of the compressor 11; then, calculate the saturated refrigerant temperature corresponding to the discharge pressure based on the refrigerant type; then, calculate the discharge superheat of the compressor 11, which is equal to the discharge temperature minus the saturated refrigerant temperature corresponding to the discharge pressure; if the discharge superheat of the compressor 11 is less than the discharge superheat set value, it is determined that the compressor 11 is experiencing hydraulic compression oil loss. Initiate the elimination of the hydraulic compression oil loss condition of the compressor 11. The hydraulic compression oil loss oil return control of the compressor 11 surpasses the chilled water return or outlet water temperature pursuit control; control the electronic expansion valve (such as... Figure 1 The first switching device V1 is opened to ensure that the refrigerant saturation temperature corresponding to the evaporation pressure of the flooded evaporator 51 is 2±1℃; the compressor 11 is loaded and operated so that its chilled water outlet temperature is not lower than 5.0±1℃, and the low-pressure switch of the compressor 11 is not activated; then, the oil return injection pump 61 of the compound oil return device RD and the auxiliary oil return circuit RDB are turned on to recover the refrigerant oil in the flooded evaporator 51 and return it to the compressor. The compressor 11 maintains the above conditions and operates for 30 minutes as one cycle; after one cycle of operation to eliminate the abnormal oil loss of the compressor 11, the steps of detecting the refrigerant discharge pressure (discharge pressure) and discharge temperature of the compressor 11 are repeated, and this cycle of operation and judgment is repeated until the oil loss of the compressor 11 is eliminated.

[0069] In summary, this invention's flooded chiller system with an oil return heat exchanger guides the oil-rich refrigerant liquid from the flooded evaporator into the pipe-side circuit of the oil return heat exchanger during compressor operation. There, it exchanges heat with the high-pressure, high-temperature refrigerant liquid from the condenser. The low-pressure, oil-rich refrigerant liquid on the pipe side gains heat from the high-pressure, high-temperature refrigerant liquid, causing it to evaporate into gas. The 5% refrigerant oil in the refrigerant liquid generates lift due to the boiling oil bubbles caused by the refrigerant evaporation, and is drawn from the pipe-side outlet into the compressor's suction inlet, achieving a non-powered oil return effect (eliminating the need for high-pressure gas). Under the same compressor suction mass flow rate, this invention's flooded chiller system with an oil return heat exchanger, compared to conventional technology, has an increased enthalpy difference, resulting in improved refrigeration effect and thus enhanced cooling capacity.

[0070] Furthermore, when the compressor operates under partial load conditions, the temperature difference between the high-pressure refrigerant liquid in the condenser and the low-pressure rich oil refrigerant liquid drawn from the self-filling evaporator narrows. As a result, the low-pressure rich oil refrigerant liquid may not evaporate completely, resulting in insufficient lift from the oil bubbles. In this case, the slightly reduced high-pressure gas is used as the power for the return oil jet pump to draw the incompletely evaporated rich oil refrigerant liquid to evaporate and return it to the compressor via the suction pipe. Moreover, because it operates under partial load conditions, the loss of cooling capacity and the impact on cooling energy efficiency are also relatively small.

[0071] Furthermore, the flooded chiller system with a return oil heat exchanger of this invention can selectively activate the return oil jet pump to assist in the return oil via the return oil pipeline assembly, depending on the return oil status. This can reduce the loss of cooling capacity and ineffective power in conventional systems that rely entirely on high-pressure gas for power.

[0072] In addition, the flooded chiller system of this utility model with an oil return heat exchanger is equipped with an oil separator return circuit, so that the refrigerant oil in the oil separator returns to the compressor. This prevents the refrigerant oil that is not intercepted by the oil separator from accumulating in the flooded evaporator with the compressor exhaust. This reduces or prevents the oil concentration in the flooded evaporator from increasing, avoids the deterioration of the evaporation temperature, and prevents the oil bubbles from gradually increasing during refrigerant boiling, which would lead to compressor liquid compression, thus avoiding oil loss in the compressor.

[0073] Although the present invention has been disclosed above by means of embodiments, it is not intended to limit the present invention. Any person skilled in the art should be able to make some modifications and refinements without departing from the spirit and scope of the present invention, but all such modifications and refinements shall fall within the protection scope of the present invention.

Claims

1. A flooded chiller system with a return oil heat exchanger, characterized in that, include: One compressor; One oil separator; A condenser; An oil return heat exchanger includes a shell, a refrigerant heat exchange inlet, a refrigerant heat exchange outlet, a heat exchange pipeline, an oil return heat exchange inlet, and an oil return heat exchange outlet. The refrigerant heat exchange inlet and the refrigerant heat exchange outlet are provided at opposite ends of the shell, and the oil return heat exchange inlet and the oil return heat exchange outlet are provided on one side of the shell. The heat exchange pipeline is located inside the shell, with one inlet end of the heat exchange pipeline connected to the oil return heat exchange inlet and one outlet end of the heat exchange pipeline connected to the oil return heat exchange outlet. A full-fill evaporator; A first switching device; as well as A refrigerant circulation pipeline assembly and an oil return pipeline assembly, wherein the refrigerant circulation pipeline assembly connects the compressor, the oil separator, the condenser, the oil return heat exchanger, the first switching device, and the flooded evaporator; It also includes a main oil return circuit, which includes a first oil return pipeline and a second oil return pipeline in the oil return pipeline group; the first oil return pipeline is connected between a refrigerant outlet of the flooded evaporator and the oil return heat exchange inlet of the oil return heat exchanger, and the second oil return pipeline is connected between the oil return heat exchange outlet of the oil return heat exchanger and a suction inlet of the compressor.

2. The flooded chiller system with a return oil heat exchanger as described in claim 1, characterized in that, Also includes: An oil return injection pump is provided. The oil return injection pump is a composite oil return device consisting of an oil return heat exchanger, an oil return injection pump, and an oil return pipeline assembly. The composite oil return device includes a main oil return circuit and an auxiliary oil return circuit. The auxiliary oil return circuit includes the oil return injection pump, the oil return heat exchanger, a third oil return pipeline, a fourth oil return pipeline, a fifth oil return pipeline in the oil return pipeline assembly, and the compressor. The third oil return pipeline is connected between the second oil return pipeline and the second inlet of the oil return injection pump of the oil return injection pump. The fourth oil return pipeline is connected between the first inlet of the oil return injection pump of the oil return injection pump and the exhaust outlet of the compressor. The fifth oil return pipeline is connected between the outlet of the oil return injection pump of the oil return injection pump and the intake inlet of the compressor.

3. The flooded chiller system with a return oil heat exchanger as described in claim 2, characterized in that: The first return oil pipeline and the fourth return oil pipeline are each equipped with at least one switching device.

4. The flooded chiller system with a return oil heat exchanger as described in claim 3, characterized in that: The at least one switching device is an electronic expansion valve or a solenoid valve.

5. The flooded chiller system with a return oil heat exchanger as described in claim 1, characterized in that, Also includes: An oil separator return circuit includes at least one switching device, an oil level detector, and a sixth return oil line in the return oil line group, wherein the oil level detector is located on the compressor, the sixth return oil line connects an oil return inlet of the compressor to an oil return outlet of the oil separator, and the at least one switching device is located on the sixth return oil line.

6. The flooded chiller system with a return oil heat exchanger as described in claim 5, characterized in that: The at least one switching device is an electronic expansion valve or a solenoid valve.

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