Compression mechanism and HVAC system equipped with the compression mechanism

Abstract

To provide a compression mechanism for an HVAC system.SOLUTION: A compression mechanism comprises a first compressor and a second compressor. The first compressor fluid-communicates with a first branch of a refrigerant suction line having the first branch and a second branch. The first compressor also fluid-communicates with a first oil discharge pipe. The second compressor fluid-communicates with the second branch of the refrigerant suction line. The second compressor fluid-communicates with a second oil discharge pipe. The second oil discharge pipe is constituted so as to send oil to the first branch and the second branch of the refrigerant suction line from the second compressor. The first oil discharge pipe is constituted so as to send the oil to only the second branch of the refrigerant suction line from the first compressor.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates generally to compressor operation and efficiency, and more particularly to balancing oil carryover among multiple compressors for heating, ventilation, air conditioning, and refrigeration systems. [Background technology]

[0002] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the embodiments described herein, to facilitate a better understanding of the various aspects of the embodiments. Accordingly, it should be understood that the following statements are to be read in this light, and not as admissions of prior art.

[0003] Modern residential and industrial customers expect their indoor spaces to be temperature controlled. Generally, heating, ventilation, and air conditioning ("HVAC") systems circulate air from an indoor space to a cold (for cooling) or hot (for heating) source, thereby regulating the ambient temperature of the indoor space. HVAC systems generate these cold and hot sources by specifically utilizing the well-known physical principle that fluids that change from gas to liquid give off heat and fluids that change from liquid to gas absorb heat.

[0004] In a typical system, a fluid refrigerant flows through a closed loop of piping using compressors and other flow control devices to regulate the refrigerant flow and pressure, thereby cycling the refrigerant between liquid and gas phases. This phase change typically occurs within an HVAC heat exchanger. A heat exchanger is part of a closed loop and is designed to transfer heat between the circulating refrigerant and the flowing ambient air. This is the basis of the refrigeration cycle. When the refrigerant changes from a gas to a liquid, the heat exchanger is called a "condenser," and the condensing fluid gives up heat to the surrounding environment. When the refrigerant changes from a liquid to a gas, the heat exchanger is called an "evaporator," and the evaporating refrigerant absorbs heat from the surrounding environment.

[0005] Compressors are the core of most HVAC equipment. They compress the refrigerant to begin the refrigeration cycle. Some systems use multiple compressors to compress the refrigerant. These multiple compressors may include both fixed-speed and variable-speed or inverter compressors. Some systems use oil to lubricate the compressor, and some of this oil may be discharged with the refrigerant. In these systems, the compressed refrigerant and the oil carried with it are sent to an oil separator. The oil separator separates the compressed refrigerant from the discharged oil. After passing through the oil separator, the compressed refrigerant is discharged to the condenser, and the separated oil is diverted from the oil separator through an oil return line to the suction line and then returned to the compressor.

[0006] The suction line is typically the piping that carries refrigerant vapor from the evaporator to the compressor. In systems using multiple compressors, the suction line may have multiple sides or branches to supply refrigerant vapor to multiple compressors.

[0007] Commercial HVAC applications with multiple compressors may benefit from using a single refrigeration circuit. However, this can result in inefficient compressor operation due to unequal oil carryover between the compressors. In systems using multiple compressors, each compressor may discharge different amounts of oil along with the compressed refrigerant. Depending on the configuration, this can result in an inappropriate amount of oil flowing from one compressor to another, resulting in excessive oil carryover and / or bypass losses.

[0008] When multiple compressors are used, a system is needed to efficiently manage oil carryover and reduce bypass losses. Summary of the Invention

[0009] Specific aspects of some embodiments disclosed herein are described below. It should be understood that these aspects are presented merely to provide the reader with a general description of certain forms the invention may take, and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that are not set forth below.

[0010] Embodiments of the present disclosure generally relate to heating, ventilation, air conditioning or refrigeration (HVACR) systems that utilize multiple compressors with a single refrigeration circuit.

[0011] Some embodiments include one or more inverter compressors in fluid communication with a first oil separator and one or more constant speed compressors in fluid communication with a second oil separator. Some embodiments include a suction line having a first side and a second side, the first side of the suction line configured to supply refrigerant to the one or more inverter compressors and the second side of the suction line configured to supply refrigerant to the one or more constant speed compressors, a first oil return line configured to route oil from the first oil separator to the second side of the suction line, and a second oil return line split to route oil from the second oil separator to both the first side and the second side of the suction line.

[0012] Some embodiments include a first compressor in fluid communication with a first branch of a refrigerant suction line having a first branch and a second branch, the first compressor also in fluid communication with a first oil discharge line, and a second compressor in fluid communication with the second branch of the refrigerant suction line and in fluid communication with a second oil discharge line, the second oil discharge line configured to deliver oil from the second compressor to the first and second branches of the refrigerant suction line, and the first oil discharge line configured to deliver oil from the first compressor to the second branch of the refrigerant suction line.

[0013] Some embodiments include a low-pressure refrigerant line having a first portion and a second portion, the first portion and the second portion of the low-pressure refrigerant line extending in different directions from a refrigerant inlet point; a first oil discharge line fluidly connecting a first compressor to a first oil separator; a first oil return line connecting the first oil separator to a second portion of the low-pressure refrigerant line via a second capillary tube; a second oil discharge line fluidly connecting a second compressor having a higher oil carryover than the first compressor to the second oil separator; and a second oil return line connecting the second oil separator to the first portion of the low-pressure refrigerant line via the first capillary tube and connecting the second oil separator to the second portion of the low-pressure refrigerant line via a third capillary tube, wherein the first capillary tube and the second capillary tube are configured to carry approximately the same amount of oil, and the third capillary tube is configured to carry more oil than either the first or second capillary tube.

[0014] Various refinements of the features described above may exist in connection with various aspects of the present embodiment. Additional features may also be incorporated into these various aspects. These refinements and additional features may exist individually or in any combination. For example, various features discussed below with respect to one or more of the illustrated embodiments may be incorporated alone or in any combination into any of the above aspects of the present disclosure. Again, the foregoing summary is not intended to limit the subject matter of the claims, but is intended only to familiarize the reader with certain aspects and circumstances of some embodiments. [Brief explanation of the drawings]

[0015] These and other features, aspects, and advantages of particular embodiments will become better understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements. [Figure 1] Schematic diagram of an HVAC system with a single compressor that discharges compressed refrigerant and circulates oil through an oil separator and suction line. [Figure 2]FIG. 1 is a schematic diagram of an HVAC system having two compressors that discharge refrigerant and oil to first and second oil separators and a first or second oil return line according to the present disclosure. [Figure 3] 1 is a schematic diagram of a particular embodiment of an HVAC system according to the present disclosure. [Figure 4] 1 is a schematic diagram of an HVAC system including an inverter compressor and a constant speed compressor according to the present disclosure. [Figure 5] 1 is a schematic diagram of an HVAC system including an inverter compressor and multiple constant speed compressors according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] One or more specific embodiments of the present disclosure are described below. For purposes of brevity in describing these embodiments, not all features of an actual device may be described herein. It should be understood that the development of any actual device, as with any engineering or design project, requires numerous device-specific decisions to achieve the developer's particular goals, including meeting system- and business-related constraints that may vary among different devices. It should also be understood that such a development effort may be complex and time-consuming, but is nevertheless a routine undertaking of design, fabrication, and manufacture for those of ordinary skill in the art having the benefit of this disclosure.

[0017] When introducing elements of various embodiments, the terms "a," "the," "said," etc. may be used, and these terms are intended to indicate the presence of one or more elements. The terms "including," "comprising," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0018] In some embodiments, an HVAC system can cool or heat indoor space air by exchanging heat between a refrigerant and the indoor space air in an HVAC heat exchanger. In another embodiment, an HVAC system can cool or heat water by exchanging heat between a refrigerant and water in an HVAC heat exchanger. The water cooled or heated in the HVAC heat exchanger can be used for air conditioning. For example, an HVAC system may have a refrigeration system that supplies a building with chilled water cooled by a refrigerant in an HVAC heat exchanger. In an HVAC system, a compressor typically removes low-pressure refrigerant from an evaporator, compresses the refrigerant into a high-temperature, high-pressure vapor, and discharges it into a condenser. Oil is used to lubricate the moving parts of the compressor. Compressor oils can be selected from the group consisting of polyalkylene glycol (PAG), polyol ester (POE), mineral oil, alkylbenzene (AB), polyvinyl ether (PVE), and R-1234yf oil. Some of the oil in the compressor is discharged from the compressor along with the high-pressure refrigerant vapor. To maintain an appropriate amount of oil in the compressor, the oil discharged with the refrigerant is returned to the compressor. The amount of oil discharged from the compressor along with the high-pressure refrigerant is called oil carryover. When oil carryover is balanced, approximately the same amount of oil is returned to the compressor as is discharged from the compressor, maintaining the desired amount of oil in the compressor.

[0019] If the compressor runs out of oil, moving parts can overheat and become damaged, while too much oil being pumped back into the compressor reduces the compressor's operating efficiency, at least in part due to fluid friction drag caused by compressor components moving through excess oil.

[0020] An oil separator can be used to separate the oil from the hot refrigerant vapor as both exit the compressor. The oil separator is placed in the discharge line between the compressor and the condenser. The flow of high-pressure refrigerant slows within the oil separator, allowing oil droplets to be trapped within the separator. The heavier oil droplets separate from the refrigerant vapor and fall to the bottom of the oil separator. The oil collected in the oil separator is returned to the compressor through an oil return line connecting the oil separator to the suction line.

[0021] Typically, a certain amount of oil is retained at the bottom of the oil separator. When the oil separator runs out of oil, some of the high-pressure refrigerant vapor passes through the oil separator and returns to the compressor suction line without being sent to the condenser. This recirculation of high-temperature, high-pressure refrigerant vapor is called bypass loss and reduces the efficiency of the entire system.

[0022] Returning to FIG. 1 , the compressor 110 discharges oil along with the high-pressure refrigerant from the compressor 110 to the oil separator 120. The oil then separates from the high-pressure refrigerant and falls to the bottom of the oil separator 120. In some embodiments, the oil passes through a filter 125 and then into the oil return line 130, where it reaches a flow restricting device, such as a capillary tube 140. The capillary tube 140 restricts the flow of oil from the oil return line 130 back to the suction line 150. The amount of oil that passes through the capillary tube is determined by the size of the capillary tube. The size of the capillary tube can control the flow rate and pressure drop of the fluid passing through the capillary tube. Once the oil passes through the suction line 150, it is returned to the compressor 110.

[0023] If the oil separator 120 discharges oil into the oil return line 130 faster than it can receive oil from the compressor 110, the oil separator 120 may become empty of oil. In this case, at least a portion of the high-pressure refrigerant vapor passes through the oil separator 120, the oil return line 130, and the capillary tube 140 and into the low-pressure suction line 150. As a result, the high-pressure refrigerant previously discharged from the compressor must be recompressed and discharged to the condenser for use in the refrigeration cycle, reducing the overall efficiency of the system.

[0024] 2 is a schematic diagram of an HVAC system according to the present disclosure. In FIG. 2, compressor A 210 has a smaller capacity and less oil carryover than compressor B 215. That is, compressor A 210 discharges less total oil along with the high-pressure refrigerant than compressor B 215. Compressor B 215 has a larger capacity than compressor A 210 and discharges more oil than compressor A 210.

[0025] The embodiment shown in FIG. 2 has a first oil discharge line 211 connecting compressor A 210 to a first oil separator 233 and a second oil discharge line 216 connecting compressor B 215 to a second oil separator 235. This embodiment has a suction line 220 having a first side 223 and a second side 225. In some embodiments, the first side 223 and the second side 225 diverge at a refrigerant inlet point 227. A first oil return line 242 connects the first oil separator to the second side 225 of the suction line 220 via a second capillary tube 254. A second oil return line 244 has a first branch 246 and a second branch 248. The first branch 246 connects the second oil separator 235 to the first side 223 of the suction line 220 via a first capillary tube 252. The second branch 248 connects the second oil separator 235 to the second side 225 of the suction line 220 via a third capillary tube 256 .

[0026] Oil discharged from compressor A 210 enters first oil separator 233, and a portion of the oil passes through first oil separator 233 to first oil return line 242. This oil is metered through second capillary tube 254 and enters second side 225 of low-pressure suction line 220. When both compressors A 210 and B 215 are operating, second side 225 of suction line 220 supplies low-pressure refrigerant and oil to compressor B 215, and first side 223 of suction line 220 supplies low-pressure refrigerant and oil to compressor A 210. When only compressor A 210 is operating and compressor B 215 is stopped, oil that enters either first side 223 or second side 225 of suction line 220 is drawn toward compressor A 210. When both compressor A 210 and compressor B 215 are operating, oil passes through the second capillary tube 254 and enters compressor B 215 via the second side 225 of the suction line 220 .

[0027] Oil discharged from compressor B 215 enters second oil separator 235, and a portion of the oil passes through second oil separator 235 to second oil return line 244. A portion of the oil that enters second oil return line 244 passes through first branch 246 of second oil return line 244, and the remaining oil that enters second oil return line 244 passes through second branch 248 of second oil return line 244. First branch 246 connects second oil return line 244 to first side 223 of suction line 220 via first capillary tube 252. Second branch 248 connects second oil return line 244 to second side 225 of suction line 220 via third capillary tube 256.

[0028] The amount of oil that passes through a capillary tube is determined by the size of the capillary tube, and by varying the size of the capillary tube, the flow rate and pressure drop of the fluid passing through the capillary tube can be controlled.

[0029] In balanced operation, the amount of oil returned to compressor A 210 is approximately the same as the amount of oil discharged from compressor A 210. The first capillary tube 252 is selected to deliver the desired amount of oil from the second oil separator 235 to the first side 223 of the suction line 220 and ultimately to compressor A 210. The desired amount of oil depends on the compressor specifications, such as compressor size, flow rate, and configuration.

[0030] The second capillary tube 254 is selected to deliver the same or approximately the same amount of oil as the first capillary tube 252. The second capillary tube 254 delivers oil from the first oil separator 233 to the second side 225 of the suction line 220. When compressor B 215 is operating, this oil passes through the second side 225 of the suction line 220 to compressor B 215. When compressor B 215 is not operating, oil is drawn from the second side 225 of the suction line 220 to the first side 223 of the suction line 220 and into compressor A 210. When compressor B 215 is not operating, compressor A 210 and the first oil return line 242 form a self-circulating path such that oil discharged by compressor A 210 returns to compressor A 210.

[0031] FIG. 3 illustrates an example of a specific embodiment according to the present disclosure. In the embodiment shown in FIG. 3, compressor A 310 discharges oil at a rate of 20 kg / h. This oil is separated from the high-pressure refrigerant by a first oil separator 333. The first oil separator 333 collects 18 kg / h of oil and discharges 2 kg / h of oil along with the high-pressure refrigerant. The 18 kg / h of oil captured in the first oil separator 333 passes through a first oil return line 342 and the second capillary tube 254 to the second side 325 of the suction line 320. In this specific embodiment, compressor B 315 discharges 60 kg / h of oil along with the high-pressure refrigerant. The second oil separator 335 collects 54 kg / h of oil and discharges 6 kg / h of oil along with the high-pressure refrigerant. The 54 kg / h of oil captured is sent to a second oil return line 344. The first branch 346 of the second oil return line carries 18 kg / h of oil via the first capillary tube 352 to the first side 223 of the suction line 220. The second branch 348 of the second oil return line carries 36 kg / h of oil via the third capillary tube 356 to the second side 325 of the suction line 320. A total of 8 kg / h of oil is discharged from the two oil separators, and this oil circulates with the high-pressure refrigerant until the oil entrained with the high-pressure refrigerant is finally returned to each compressor through the suction line 320. It will be appreciated that the larger-capacity compressor B draws a greater amount of the 8 kg / h of oil supplied via the suction line than the smaller-capacity compressor A. This rate is approximately equal to the rate at which each compressor loses oil from the first or second oil separator. In the embodiment shown in FIG. 3, 2 kg / h of oil flows from the suction line 320 to the first side 323 of the suction line 320 and 6 kg / h of oil flows to the second side 325 of the suction line 320 .

[0032] 3, the amount of oil passing through the first capillary tube 352 to the first side 323 of the suction line 320 and the amount of oil passing through the second capillary tube 354 to the second side 325 of the suction line 320 are approximately the same. The third capillary tube 356 is configured to pass 36 kg / h of oil from the second branch 348 of the second oil return line to the second side 325 of the suction line 320. In other words, the third capillary tube 356 is configured to pass a larger oil flow compared to the first capillary tube 352 or the second capillary tube 354.

[0033] When both compressors A and B are operating, this configuration provides 18 kg / h of oil from the second oil separator 335 to compressor A 310. This configuration provides 18 kg / h of oil from the first oil separator 333 and 36 kg / h of oil from the second oil separator 335 to compressor B 315.

[0034] When compressor B shuts down, oil discharge to the second oil separator 335 stops. In this situation, the 18 kg / h of oil discharged from the first oil separator 333 to the second side 325 of the suction line 320 is drawn back to compressor A 310 through the first side 323 of the suction line 320. Whether compressor B 315 is running or not, the disclosed configuration provides a balanced 18 kg / h of oil to compressor A 310. It should be understood that during startup and / or shutdown of compressor B 315, oil flow may be temporarily interrupted until the system rebalances.

[0035] Figure 4 is a schematic diagram illustrating one embodiment according to the present disclosure. As shown in Figure 4, in some embodiments, compressor A 410 may be a variable speed inverter compressor, while compressor B 415 is a constant speed compressor. By sizing compressors A 410 and B 415 in a particular way, it is possible to combine a single variable speed compressor with a similarly sized constant speed compressor to create virtually any flow rate, from the lowest flow rate possible using only the inverter compressor to the maximum combined output of the variable and constant speed compressors.

[0036] FIG. 5 is a schematic diagram illustrating an embodiment in which Compressor B has multiple constant-speed compressors 515, 517, and 519. In some embodiments, each constant-speed compressor can be activated and deactivated to generate the desired refrigerant flow throughout the system. In some embodiments, each constant-speed compressor 515, 517, and 519 discharges high-pressure refrigerant and any associated oil to a second oil separator 535. That is, in some embodiments, the HVAC system has at least two constant-speed compressors in fluid communication with a single second oil separator 535. Each constant-speed compressor 515, 517, and 519 may also be connected to a second side of suction line 525. Thus, the operating principles for achieving balanced oil carryover described herein are equally applicable to embodiments using a single constant-speed compressor and embodiments using multiple constant-speed compressors. In other embodiments, Compressor A may have multiple inverter compressors.

[0037] Depending on the size of the constant speed compressors and inverter compressors, such a configuration can be used to generate a wide range of flow rates, ranging from a minimum flow rate generated by the inverter compressor alone to a maximum flow rate generated by the inverter compressor combined with all of the constant speed compressors, depending on the situation.

[0038] Although the general concept of the disclosed compressor oil return system has been described with reference to several specific embodiments, it will be appreciated that many variations are contemplated.

[0039] While aspects of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

1. 1. A compression mechanism for an HVAC system, comprising: a first compressor in fluid communication with a first branch of a refrigerant suction line having a first branch and a second branch, the first compressor also in fluid communication with a first oil discharge pipe; a second compressor in fluid communication with the second branch of the refrigerant suction line and in fluid communication with a second oil discharge pipe; Equipped with the second oil discharge pipe is configured to deliver oil from the second compressor to the first branch and the second branch of the refrigerant suction line, and the first oil discharge pipe is configured to deliver oil from the first compressor only to the second branch of the refrigerant suction line. Compression mechanism.

2. The first compressor is an inverter compressor, and the second compressor is a constant speed compressor. The compression mechanism according to claim 1 .

3. The oil carryover of the first compressor is less than the oil carryover of the second compressor. The compression mechanism according to claim 1 or 2.

4. the second oil discharge pipe includes a second oil discharge pipe first branch configured to deliver oil from the second oil discharge pipe to the first branch of the refrigerant suction line, and a second oil discharge pipe second branch configured to deliver oil from the second oil discharge pipe to the second branch of the refrigerant suction line; The compression mechanism according to claim 1 or 2.

5. The oil discharge device further includes a first capillary tube in fluid communication with the second oil discharge pipe first branch of the second oil discharge pipe, a second capillary tube in fluid communication with the first oil discharge pipe, and a third capillary tube in fluid communication with the second oil discharge pipe second branch of the second oil discharge pipe. The compression mechanism according to claim 4.

6. the first capillary tube and the second capillary tube are configured to pass substantially the same oil flow; The compression mechanism according to claim 5.

7. The third capillary tube is configured to allow a greater oil flow therethrough than the first capillary tube or the second capillary tube. The compression mechanism according to claim 5.

8. At least two of the second compressors are included, the at least two second compressors are in fluid communication with the single second oil discharge pipe; The compression mechanism according to claim 2 .

9. The first compressor is one unit. The compression mechanism according to claim 2 .

10. further comprising a compressor oil selected from the group consisting of polyalkylene glycol (PAG), polyol ester (POE), mineral oil, alkyl benzene (AB), and polyvinyl ether (PVE); The compression mechanism according to claim 1 .

11. The compression mechanism according to claim 1; the refrigerant suction line having the first branch and the second branch; a first oil discharge pipe in fluid communication with the first compressor and configured to deliver oil only from the first compressor to the second branch of the refrigerant suction line; a second oil discharge pipe in fluid communication with the second compressor and configured to deliver oil from the second compressor to the first branch and the second branch of the refrigerant suction line; An HVAC system comprising:

12. further comprising a chiller system configured to provide chilled water to the building; 12. The HVAC system of claim 11.

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