Compression mechanism and HVAC system having 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 between 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, and as such, 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. Typically, heating, ventilation, and air conditioning ("HVAC") systems circulate air from an indoor space to a source of low temperature (for cooling) or high temperature (for heating), thereby regulating the ambient temperature of the indoor space. HVAC systems generate these sources of low and high temperature by specifically taking advantage of a well-known physical principle: fluids that change from a gas to a liquid give off heat, and fluids that change from a liquid to a 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 in 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 outside air. This is the basis of the refrigeration cycle. If 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. If 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 are responsible for compressing the refrigerant to start the cooling cycle. In some systems, multiple compressors are used 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 compressors, and some of this oil may be discharged with the refrigerant. In such systems, the compressed refrigerant and the oil carried with the compressed refrigerant 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 back to the compressor.

[0006] The suction line is typically the piping that carries refrigerant vapor from the evaporator to the compressor. In systems that use 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 cooling 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. In some configurations, this can result in an inappropriate amount of oil flowing from one compressor to another, which can result 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 of the embodiments disclosed herein are described below. It should be understood that these aspects are merely set forth 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 described 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 and second sides 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 drain, and a second compressor in fluid communication with a second branch of the refrigerant suction line and in fluid communication with a second oil drain, the second oil drain 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 drain 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 the 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 carry-over 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, the first capillary tube and the second capillary tube being configured to carry approximately the same amount of oil through them, and the third capillary tube being configured to carry more oil through it than the first capillary tube or the second capillary tube.

[0014] Various refinements of the features described above may exist in relation to the various aspects of the present embodiment. These various aspects may also incorporate additional features. These refinements and additional features may exist individually or in any combination. For example, the various features discussed below with respect to one or more illustrated embodiments may be incorporated alone or in any combination into any of the above aspects of the present disclosure. Again, the above 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 description of the drawings]

[0015] These and other features, aspects, and advantages of certain 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 and in which: [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. [Diagram 2]FIG. 1 is a schematic diagram of an HVAC system having two compressors that discharge refrigerant and oil to a first and second oil separator and a first or second oil return line according to the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram of a particular embodiment of an HVAC system according to the present disclosure. [Figure 4] FIG. 1 is a schematic diagram of an HVAC system including an inverter compressor and a constant speed compressor according to the present disclosure. [Diagram 5] FIG. 1 is a schematic diagram of an HVAC system including an inverter compressor and multiple constant speed compressors in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] One or more specific embodiments of the present disclosure are described below. To simplify the description of 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 in any engineering or design project, requires numerous device-specific decisions to be made to achieve the developer's particular goals, such as meeting system-related and business-related constraints that may vary between different devices. Moreover, it should be understood that such development efforts may be complex and time-consuming, but are nevertheless routine activities 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 words "a," "the," "said," etc. may be used, which are intended to indicate the presence of one or more of the 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, the HVAC system can cool or heat the air in the indoor space by exchanging heat between the refrigerant and the air in the indoor space in the HVAC heat exchanger. In another embodiment, the HVAC system can cool or heat water by exchanging heat between the refrigerant and water in the HVAC heat exchanger. The water cooled or heated in the HVAC heat exchanger can be used for air conditioning. For example, the HVAC system may have a cooling system that supplies a building with chilled water cooled by the refrigerant in the HVAC heat exchanger. In the HVAC system, the compressor typically removes low pressure refrigerant from the evaporator and compresses the refrigerant into high temperature and high pressure vapor and discharges it to the condenser. Oil is used to lubricate the moving parts of the compressor. The compressor oil 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. A portion of the oil in the compressor is discharged from the compressor 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 together with the high-pressure refrigerant is called oil carryover. When the oil carryover is balanced, the desired amount of oil is maintained in the compressor because the amount of oil returned to the compressor is roughly the same as the amount discharged from the compressor.

[0019] If the compressor runs out of oil, the moving parts can overheat and become damaged, while if too much oil is pumped back into the compressor, it will operate less efficiently, at least in part due to the fluid friction drag created by the 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 high pressure refrigerant flow slows in the oil separator, allowing the oil droplets to be trapped in the oil separator. The heavier oil droplets separate from the refrigerant vapor and fall to the bottom of the oil separator. The oil that collects in the oil separator is returned to the compressor through an oil return line that connects the oil separator to the suction line.

[0021] Usually, 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 may pass through the oil separator and return to the compressor suction line instead of being sent to the condenser. This recirculation of high-temperature, high-pressure refrigerant vapor is called bypass loss, which leads to a decrease in 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 is then separated 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 run out 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 by the compressor must be compressed again and discharged to the condenser for use in the cooling cycle, reducing the efficiency of the entire 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 together 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 the first oil separator 233 and a portion of the oil passes through the first oil separator 233 to the first oil return line 242. This oil is metered through the second capillary tube 254 and enters the second side 225 of the low pressure suction line 220. When both compressor A 210 and compressor B 215 are operating, the second side 225 of the suction line 220 supplies low pressure refrigerant and oil to compressor B 215 and the first side 223 of the 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 the first side 223 or the second side 225 of the suction line 220 is drawn towards 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] The oil discharged from compressor B 215 enters the second oil separator 235, and a portion of the oil passes through the second oil separator 235 to the second oil return line 244. A portion of the oil that entered the second oil return line 244 passes through a first branch 246 of the second oil return line 244, and the remaining oil that entered the second oil return line 244 passes through a second branch 248 of the second oil return line 244. The first branch 246 connects the second oil return line 244 to the first side 223 of the suction line 220 via a first capillary tube 252. The second branch 248 connects the second oil return line 244 to the second side 225 of the suction line 220 via a third capillary tube 256.

[0028] The amount of oil that passes through a capillary depends on the size of the capillary, and by varying the size of the capillary, the flow rate and pressure drop of the fluid passing through the capillary 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 by compressor A 210. The first capillary tube 252 is selected to deliver a 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, the 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 the first oil separator 333. The first oil separator 333 collects 18 kg / h of oil and discharges 2 kg / h of oil with the high pressure refrigerant. The 18 kg / h of oil captured in the first oil separator 333 is sent through the first oil return line 342 and through the second capillary tube 254 to the second side 325 of the suction line 320. In this particular embodiment, compressor B 315 discharges 60 kg / h of oil with the high pressure refrigerant. The second oil separator 335 collects 54 kg / h of oil and discharges 6 kg / h of oil with the high pressure refrigerant. The 54 kg / h of oil captured is sent to the second oil return line 344. The first branch 346 of the second oil return line carries 18 kg / h of oil to the first side 223 of the suction line 220 via the first capillary tube 352. The second branch 348 of the second oil return line carries 36 kg / h of oil to the second side 325 of the suction line 320 via the third capillary tube 356. A total of 8 kg / h of oil is discharged from the two oil separators, which circulate together with the high pressure refrigerant until the oil entrained in the high pressure refrigerant is finally returned to each compressor through the suction line 320. It will be seen that the large capacity compressor B draws in a larger amount of the 8 kg / h of oil supplied through the suction line than the small capacity compressor A. This proportion is approximately equal to the proportion 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 a first side 323 of the suction line 320 and 6 kg / h of oil flows to a 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. That is, 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 to compressor A 310 from the second oil separator 335. 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, the 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 configuration of the present disclosure provides a balanced 18 kg / h of oil to compressor A 310. It should be understood that during start-up and / or shutdown of compressor B 315, the oil flow may be temporarily interrupted until the system rebalances.

[0035] 4 is a schematic diagram showing an embodiment according to the present disclosure. As shown in FIG. 4, in some embodiments, compressor A 410 may be a variable speed inverter compressor, while compressor B 415 is a fixed speed compressor. By sizing compressor A 410 and compressor B 415 in a particular way, it is possible 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 fixed speed compressors combined, by combining one variable speed compressor with a similarly sized fixed speed compressor.

[0036] FIG. 5 is a schematic diagram illustrating an embodiment in which compressor B has multiple constant-speed compressors 515, 517, 519. In some embodiments, each constant-speed compressor can be turned on and off to generate a desired refrigerant flow throughout the system. In some embodiments, each constant-speed compressor 515, 517, 519 discharges high-pressure refrigerant and any associated oil to a second oil separator 535. That is, in some embodiments, the HVAC has at least two constant-speed compressors in fluid communication with a single second oil separator 535. Each constant-speed compressor 515, 517, 519 may further be connected to a second side of the suction line 525. Thus, the principles of operation that result in balanced oil carryover described herein can be equally applied to embodiments using a single constant-speed compressor and to 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 compressor and the inverter compressor, a wide range of flow rates can be produced using such a configuration, ranging from a minimum flow rate produced by the inverter compressor alone to a maximum flow rate produced by the inverter compressor in combination with all 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 drain 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 line; 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 of 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 pipe 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 of claim 4.

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

7. The third capillary tube is configured to pass a greater amount of oil flow therethrough compared to 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 a single second oil discharge pipe. The compression mechanism of claim 2.

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

10. further comprising a compressor oil selected from the group consisting of polyalkylene glycols (PAGs), polyol esters (POEs), mineral oils, alkyl benzenes (ABs), and polyvinyl ethers (PVEs); The compression mechanism of claim 1 .

11. A compression mechanism according to claim 1 ; the refrigerant suction line having the first branch and the second branch; a first oil drain 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 drain 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; The HVAC system includes:

12. and further comprising a chiller system configured to provide chilled water to the building.

12. The HVAC system of claim 11.

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