Vapor compression systems including liquid refrigerant atomizers and methods of operation and control thereof

Abstract

A vapor compression system includes a compressor including a compression stage for compressing a working fluid; a first heat exchanger located downstream of the compressor, the first heat exchanger receiving and cooling a working fluid; a second heat exchanger located downstream of the first heat exchanger and upstream of the compressor, the second heat exchanger receiving and heating the working fluid; and a reservoir positioned between the second heat exchanger and the compression stage. The reservoir defines an internal volume for containing a vapor phase and a liquid phase of the working fluid, and the reservoir includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the reservoir and flow toward the compression stage. The reservoir atomizes a liquid phase of the working fluid into droplets and introduces the droplets into a vapor phase of the working fluid exiting the reservoir.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 493,878, filed April 3, 2023, the entire disclosure of which is incorporated by reference herein. TECHNICAL FIELD

[0003] The field is vapor compression systems, and more specifically, the field is vapor compression systems including an atomizer for introducing a liquid phase working fluid into a low pressure vapor phase working fluid stream in a controlled manner. BACKGROUND

[0004] Vapor compression systems are widely used in climate control applications to provide heat pump, refrigeration, and / or air conditioning functions. A typical vapor compression system includes a fluid circuit having a first heat exchanger (e.g., a condenser that changes the phase of refrigerant from a gas / vapor phase to a liquid), a second heat exchanger (e.g., an evaporator that changes the phase of refrigerant from a liquid to a gas / vapor phase), an expansion device disposed between the first and second heat exchangers, and a compressor operating to circulate and pressurize a gas / vapor phase working fluid (and optionally a lubricating oil) between the first and second heat exchangers (e.g., the condenser and evaporator). The compressor is typically a mechanical compressor that pressurizes the working fluid, which can then be condensed and evaporated as it circulates within the system to transfer heat into or out of the system.

[0005] The working fluid in many vapor compression systems is a refrigerant that is capable of undergoing the desired phase changes of a vapor compression cycle. A challenge of vapor compression technology is to reduce the environmental impact of the refrigerant. Recently, new low global warming potential (GWP) refrigerants have been introduced. The new low global warming potential refrigerants, particularly blends, can introduce various challenges to the system that can need to be mitigated. Some potential challenges include, for example: (1) newer refrigerants typically have higher discharge temperatures; (2) options with GWP less than 150 (e.g., R454C, R455A, R457A, R468A) have higher glide than R410A, and some blends have an excessive proportion of glide in the last 5-10% of the phase change region; (3) options with GWP less than 150 (e.g., R454C, R455A, R457A, R468A) have lower density than R410A, and R1234ze has lower density than R134a. With the use of new refrigerants, the evaporator portion required to perform the superheat function can increase as the new refrigerants drive lower evaporator performance; and the natural option CO2 has a higher discharge temperature as CO2 is supercritical at discharge.

[0006] Another challenge with vapor compression technology is that the vapor is compressed and passes through the compressor in only a few milliseconds. The gas has little time (or area) to exchange heat with the environment. Therefore, the compression process is assumed to be adiabatic. However, from a thermodynamic perspective, isothermal (constant temperature) compression can be up to about 30% more efficient than adiabatic compression.

[0007] There is a need for improvements to vapor compression technology that overcome the aforementioned technical challenges in an economically efficient manner and limit or even prevent negative environmental impacts, improve compression efficiency, reduce system complexity and part count, reduce overall footprint of the system, and other advantages.

[0008] This section provides an introduction to various aspects of the field that can be related to various aspects of the present disclosure described and / or claimed below. This discussion is provided for support in better understanding various aspects of the present disclosure. As such, these statements are to be read in that light, not as an admission of prior art. SUMMARY

[0009] One aspect is a vapor compression system that circulates a working fluid. The system includes a compressor that includes a compression stage to compress the working fluid, a first heat exchanger downstream of the compressor that receives and cools the working fluid, a second heat exchanger downstream of the first heat exchanger and upstream of the compressor that receives and heats the working fluid, and a reservoir positioned between the second heat exchanger and the compression stage. The reservoir defines an internal volume to contain a vapor phase and a liquid phase of the working fluid, and the reservoir includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the reservoir and flow toward the compression stage. The reservoir is operable to atomize the liquid phase of the working fluid into droplets and introduce the droplets into the vapor phase of the working fluid that exits the reservoir.

[0010] Another aspect is a method of operating a vapor compression system that includes a compressor, a first heat exchanger, a second heat exchanger, and a reservoir. The method includes compressing a working fluid at a compression stage of the compressor, cooling the working fluid at the first heat exchanger downstream of the compressor, heating the working fluid at the second heat exchanger downstream of the first heat exchanger, delivering the working fluid into an internal volume of the reservoir downstream of the second heat exchanger and upstream of the compression stage, where the working fluid in the internal volume includes a liquid phase and a vapor phase, delivering the vapor phase of the working fluid from the reservoir toward the compression stage, and atomizing the liquid phase of the working fluid into droplets and introducing the droplets into the vapor phase that is delivered toward the compression stage using the reservoir.

[0011] Another aspect is a vapor compression system that circulates a working fluid that includes a vapor phase and a liquid phase. The system includes a scroll compressor that includes a compression stage for compressing the working fluid, a first heat exchanger downstream of the compressor that receives and cools the working fluid, a second heat exchanger downstream of the first heat exchanger and upstream of the compressor that receives and heats the working fluid, an atomizer configured to generate liquid droplets of the liquid phase of the working fluid and positioned to introduce the liquid droplets into the vapor phase of the working fluid upstream of the compression stage, and a controller connected to the atomizer and configured to control an amount of the liquid droplets introduced into the vapor phase of the working fluid based on a volumetric ratio of the scroll compressor.

[0012] There are various improvements to the features noted above with respect to the aspects mentioned above. Other features can also be incorporated into the aspects described above. These improvements and additional features can exist alone or in any combination. For example, each of the features discussed below with respect to any of the illustrated embodiments can be incorporated into any of the aspects described above, alone or in any combination. BRIEF DESCRIPTION OF DRAWINGS

[0013] Features and aspects of embodiments are described below with reference to the accompanying drawings, in which elements are not necessarily drawn to scale.

[0014] Figure 1 is a schematic diagram of an example of a vapor compression system;

[0015] Figure 2 is a cross-section of a scroll compressor for use with the vapor compression system of Figure 1

[0016] Figure 3 is a schematic diagram of another example of a vapor compression system;

[0017] Figure 4 is a schematic cross-section of an example of an accumulator or vapor-liquid separation vessel that can be included in the vapor compression system of Figure 1 and Figure 3

[0018] Figure 5 is a schematic cross-section of another example of an accumulator or vapor-liquid separation vessel that can be included in the vapor compression system of Figure 1 and Figure 3

[0019] Figure 6 is an example of a method of operating a vapor compression system;

[0020] Figure 7 is a schematic diagram of an example of a vapor compression system; Figure 1 and Figure 3 ​​​a schematic block diagram of an example of a controller used in a vapor compression system; and

[0021] Figures 8 to 10 are control algorithms that can be implemented by the controller of Figure 7

[0022] Throughout the drawings, corresponding reference numerals indicate corresponding parts. DETAILED DESCRIPTION

[0023] Figure 1 is a schematic diagram of a vapor compression system 100. In some examples, the vapor compression system 100 is implemented as, or as part of, a heating, ventilation, and air conditioning (HVAC) system, a refrigeration system, and / or a heat pump. The system 100 includes a first heat exchanger 102, a second heat exchanger 104, a compressor 106, and an expansion device 108. The system 100 also includes a working fluid circuit 110 that circulates a working fluid, such as a refrigerant, between the first heat exchanger 102, the compressor 106, the second heat exchanger 104, and the expansion device 108. The system 100 can include additional or other components than those shown and described with reference to FIG. 1. Figure 1

[0024] ​​The working fluid includes at least one refrigerant suitable for use in a vapor compression cycle. Non-limiting examples of suitable refrigerants include natural refrigerants (e.g., carbon dioxide, water, ammonia, hydrocarbons, etc.), fluorocarbon-based refrigerants, and refrigerants with low global warming potential such as ASHRAE Class Al and A2L refrigerants. Non-limiting examples of Al refrigerants include: carbon dioxide (R-744); monochlorodifluoromethane (R-22); 1,1-difluoroethane (R152a); 1,1,1,2-tetrafluoroethane (R134A); and R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125)); and trifluoromonochloropropene (R-1233), which includes cis and trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd) isomers (HFO-1233zd(Z) and HFO-1233zd(E)); and hexafluorobutene (HFO-1336, including HFO-1336mzz(Z), 1336mzz(E)). Non-limiting examples of A2L refrigerants include difluoromethane (R-32) and hydrofluoroolefins (HFOs). Suitable HFO refrigerants are described, for example, in U.S. Patent No. 4,788,352 to Smutny and U.S. Patent No. 8,444,874 to Singh et al., the relevant portions of which are incorporated herein by reference. The HFOs can include 2,3,3,3-tetrafluoroprop-l-ene (HFO-1234yf) and trans- 1,3,3,3-tetrafluoroprop-l-ene (HFO-1234ze).Non-limiting suitable examples of specific HFO refrigerants include: 3,3,3,- trifluoropropene (HFO-1234zf); HFO-1234 refrigerants such as 2,3,3,3,- tetrafluoropropene (HFO-1234yf), 1,2,3,3,-tetrafluoropropene (HFO-1234ze), cis and trans-1,3,3,3,-tetrafluoropropene (HFO-1234ye); pentafluoropropene (HFO-1225) such as 1,1,3,3,3, pentafluoropropene (HFO-1225zc); hexafluorobutene (HFO-1336) such as cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z) and trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)); or those with hydrogen on the terminally unsaturated carbon such as 1,2,3,3,3, pentafluoropropene (HFO-1225yez); fluorochloropropenes such as trifluoromonochloropropene (HFO-1233) such as CF3CCl=CH2(HFO-1233xf) and CF3CH=CHCl (HFO-1233zd) (including the trans (E) and cis (Z) isomers (HFO-1233zd(E) and HFO-1233zd(Z)), (E)-1,2-difluoroethylene (R-1132(E)); and any combination thereof. In certain aspects, the HFO refrigerant can be selected from the group consisting of R-1234yf, R-1234ze, R1233zd(E), R1233zd(Z), R1336mzz(Z), R1336mzz(E), R-1132(E), and combinations thereof. In some examples, these refrigerants are used in combination with other Al or A2L refrigerants or yet other refrigerants such as A3 or Bl or B2 refrigerants, including natural or flammable refrigerants (e.g., dimethyl ether (R-E170) or propane (C3H8 or R-290).

[0025] In some examples, the vapor compression system 100 operates using a working fluid that includes a refrigerant blend of at least two refrigerants. Suitable refrigerant blends, as well as suitable climate control systems for use with such refrigerant blends, are described in U.S. Patent Application No. 17 / 507,403 to Welch et al., filed October 21, 2021, and published as U.S. Publication No. 2023 / 0130167 on April 27, 2023, the entire disclosure of which is incorporated herein by reference. Vapor compression systems 100, as well as Figure 3Features of the vapor compression system 300 shown and described below can be used in any combination with the systems described in U.S. Publication No. 2023 / 0130167. In certain examples, the refrigerant blend includes an Al refrigerant, such as carbon dioxide (R-744), mixed with at least one other refrigerant. Carbon dioxide refrigerants are desirable for use in subcritical system designs. One example of a suitable non-limiting refrigerant blend includes CO2 (R-744) as a higher volatility high pressure refrigerant mixed with an HFO refrigerant (such as R-1233zd(E)) as a lower volatility lower pressure fluid. The refrigerant blend can be a “high glide” refrigerant blend having a first refrigerant (e.g., CO2) having a relatively lower normal boiling point (at a pressure of 1 atmosphere (atm.)) and a second refrigerant having a relatively higher normal boiling point. The difference between the normal boiling point of the first refrigerant and the normal boiling point of the second refrigerant is greater than or equal to 25 °C. As a non-limiting example, when the refrigerant blend includes CO2 having a normal boiling point of about -78 °C at 1 atm and R-1233zd(E) having a normal boiling point of about 18 °C at 1 atm, the boiling point difference is about 96 °C.

[0026] Suitable working fluid refrigerant blends include a refrigerant selected from the group consisting of R-744, R-22, R134A, R410A, R-1234yf, R-1234ze, R1233zd(E), R1233zd(Z), R1336mzz(Z), R1336mzz(E), and combinations thereof. Alternatively, the first refrigerant and the second refrigerant included in the refrigerant blend are independently selected from the group consisting of R-744, R-22, R152a, R134A, R410A, R-E170, R-32, HFO, R-290, and combinations thereof. In some examples, the first refrigerant is selected from the group consisting of R-744, R-22, R134A, R410A, R-E170, R-32, HFO, and combinations thereof, and the second refrigerant is selected from the group consisting of 2,3,3,3-tetrafluoroprop-l-ene (R-1234yf), 1,3,3,3-tetrafluoroprop-l-ene (R-1234ze), 1-chloro-3,3,3-trifluoropropene (HFO-1233zd(E)), 1-chloro-3,3,3-trifluoropropene (HFO-1233zd(Z)), 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), and combinations thereof.

[0027] The working fluid can include one or more refrigerants in combination with a refrigeration lubricating oil, such as the refrigerants described above. For example, the working fluid can include a synthetic oil. In some examples, the lubricating oil can include a polyvinylether (PVE) oil, a polyalphaolefin (PAO), a polyalkylene glycol (PAG), an alkylbenzene, a mineral oil, or an ester-based oil such as a polyol ester (POE) oil. POE oils can be suitably used in the presence of carbon dioxide (R-744) in the working fluid (e.g., in a refrigerant blend). Suitable POE oils can include compounds formed from a carboxylic acid and a polyol. Such POE compounds can be formed from a carboxylic acid selected from the group including n-pentanoic acid, 2-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, 3,3,5-trimethylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid, n-nonanoic acid, and iso-nonoanoic acid, and combinations thereof, and a polyol selected from the group including pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylpropanol, and combinations thereof.

[0028] The first and second heat exchangers 102, 104 are each operable to transfer heat between the working fluid in the circuit 110 and another fluid (e.g., air surrounding the respective heat exchanger 102, 104). The heat exchangers 102, 104 each include a heat exchange coil 112, 114 through which the working fluid in the circuit 110 is routed, respectively. Alternatively, one or both of the heat exchangers 102, 104 can include concentric tubes (or shell and tube), finned tube, brazed plate, plate and frame, microchannel, or any other suitable heat exchanger design to enable the heat exchanger to function as described. The heat exchangers 102, 104 are equipped with or used in conjunction with one or more fans or blowers (not shown) that are operable to force fluid (e.g., air) streams 116, 118 through the coils 112, 114, respectively. One of the first and second heat exchangers 102, 104 is located indoors, and one of the heat exchangers 102, 104 is located outdoors. In this example, the first heat exchanger 102 is an indoor unit that operates to exchange heat between an indoor air stream 116 and the working fluid in the coil 112, and the second heat exchanger 104 is an outdoor unit that operates to exchange heat between an outdoor air stream 118 and the working fluid in the coil 114.

[0029] In operation of the vapor compression system 100, the first heat exchanger 102 operates as an evaporator, transferring heat from the first fluid (e.g., air) stream 116 flowing through the coil 112 to the working fluid. The second heat exchanger 104 operates as a condenser, transferring heat from the working fluid flowing through the coil 114 to the second fluid (e.g., air) stream 118. In some examples, the operational mode of the vapor compression system 100 is reversible, such that the first heat exchanger 102 operates as a condenser and the second heat exchanger 104 operates as an evaporator.

[0030] The expansion device 108 is positioned between the second heat exchanger 104 and the first heat exchanger 102 and operates to expand or depressurize the working fluid at this stage of the vapor compression system 100. The expansion device 108 is an expansion valve (e.g., a thermal expansion valve). Alternatively, the expansion valve 108 is any suitable expansion device, such as, for example, an orifice or a capillary tube.

[0031] The condition (e.g., temperature and pressure) of the working fluid is monitored at one or more stages of the circuit 110. For example, the condition of the working fluid is monitored upstream of the compressor 106 (or compression stage 120) using one or more sensors 130 and downstream of the compressor 106 (or compression stage 120) using one or more sensors 132. The sensors 130 and 132 include temperature sensors and pressure sensors. Each sensor 130, 132 can be used to monitor both temperature and pressure, or each of the sensors 130, 132 can include separate devices (e.g., separate sensors) for monitoring temperature and pressure. The sensors 130, 132 can additionally and / or alternatively include any suitable device for monitoring the condition of the working fluid, such as, for example, a flow meter. Figure 1 The location of the sensors 130, 132 in the vapor compression system 100 is not limiting. The sensors 130, 132 can be located at any suitable location on the circuit 110, such as positioned along conduits connecting the working components of the vapor compression system 100. In some examples, the vapor compression system 100 includes sensors (e.g., the sensors 130, 132) positioned to monitor the condition of the working fluid at two or more stages of the circuit 110. In various examples, the vapor compression system 100 includes sensors (e.g., the sensors 130, 132) positioned to monitor the condition of the working fluid upstream and downstream of one, some, or each working component of the vapor compression system 100 (e.g., the first heat exchanger 102, the second heat exchanger 104, the compressor 106, and / or the expansion device 108).

[0032] The vapor compression system 100 also includes a controller 134 communicatively connected to various components of the system 100, such as, for example, the compressor 106 and the sensors 130, 132, among other components of the system. While a single controller 134 is shown and described, in some examples the controller 134 includes multiple controllers 134. The multiple controllers 134 can be centralized or decentralized. The controller 134 controls various aspects and parameters of the vapor compression system 100 during operation. Some of the control functions of the controller 134 will be described below.

[0033] The controller 134 receives feedback information from one or more sensors, such as the sensors 130, 132, as well as monitored process information and other information for continuous, periodic, or intermittent monitoring of conditions within the vapor compression system 100, such as the temperature and / or pressure of the working fluid at one or more stages of the vapor compression cycle. The controller 134 includes a communication interface to communicatively couple the controller 134 to one or more components of the vapor compression system 100 via one or more connections 136. The one or more connections 136 communicatively couple the controller 134 to the compressor 106, the sensors 130, 132, and / or other components of the system 100. The communication interface includes, for example, a wireless data transceiver for use with a mobile telecommunications network and / or a wired or wireless network adapter. In this way, the one or more connections 136 communicatively couple the controller 134 to one or more components of the system 100 via wired and / or wireless connections.

[0034] The compressor 106 is positioned between the first heat exchanger 102 and the second heat exchanger 104 and includes one or more compression stages 120 that operate to compress or pressurize the working fluid at this stage of the vapor compression system 100. The compressor 106 can be any suitable compressor, including but not limited to a scroll compressor, a reciprocating compressor, a rotary compressor, a screw compressor, and a centrifugal compressor. In various examples, the compressor 106 is a scroll compressor. Scroll compressors are known and are commercially available, for example, from Copeland LP (Sidney, OH, US).

[0035] Referring to Figure 2FIG. 1 shows a simplified schematic diagram illustrating a non-limiting example of a scroll compressor 200. The scroll compressor 200 includes a compressor housing 202 forming a sealed cavity within which compression of a working fluid is accomplished. The compressor housing 202 includes a casing 204, an end cap 206 positioned at one end of the casing 204, and a base 210 positioned at an opposite end of the casing 204. The scroll compressor 200 has any suitable scroll compressor design, such as a floating orbit design, a floating non-orbit design, a co-rotating design, or another suitable scroll compressor design.

[0036] The compressor 200 includes a compression stage 212 at which compression of the working fluid is accomplished. The compression stage 212 includes a fixed scroll 214 and an orbiting scroll 216 operably engaged with a motor assembly 218. The compression stage is connected with a first chamber 208 and a second chamber 220 of the compressor housing 202. The first chamber 208 at a first pressure (e.g., suction pressure) is defined by the casing 204. The second chamber 220 at a second pressure (e.g., discharge pressure) is defined by the end cap 206. A partition 222 (e.g., a muffler plate) separates the first chamber 208 and the second chamber 220. In some examples, the partition 222 restricts or prevents the working fluid from prematurely flowing between the first chamber 208 and the second chamber 220 without first being compressed via the compression stage 212.

[0037] The motor assembly 218 includes a stator 224 and a rotor 226. The compressor 200 also includes a drive shaft 228 that can be press fit within the rotor 226. The rotor 226 transmits rotational power to the drive shaft 228. The motor assembly 218 is a variable speed motor for rotating the drive shaft 228 at any of a plurality of speeds. Alternatively, the motor assembly 218 is a fixed speed motor. In the example compressor 200, the motor assembly 218 is positioned within the casing 204. The compressor 200 is alternatively an open drive compressor driven by a motor assembly positioned outside of the compressor housing 202. The drive shaft 228 is rotatably supported in the compressor housing 202 by a bearing assembly (not shown), such as a rolling element bearing, a journal bearing, or another suitable bearing type.

[0038] The fixed scroll 214 and the orbiting scroll 216 include spiral wrap that engages (or meshes) with one another, thereby forming a series of moving fluid chambers. The fluid chambers defined by the scrolls 214, 216 decrease in volume as they move from a radially outer position (e.g., at suction pressure) to a radially inner position (e.g., at a higher discharge pressure than suction pressure) throughout a compression cycle. A discharge passage 230 extends through the fixed scroll 214 and the partition 222. The discharge passage 230 communicates with at least one of the fluid chambers at the radially inner position and allows the flow of compressed working fluid, such as refrigerant or a mixture of refrigerant and lubricant (at or near discharge pressure), through the discharge passage 230 and into the second chamber 220.

[0039] The orbiting scroll 216 also includes a cylindrical hub 232 that projects downwardly and interfaces with a main bearing housing 234. The cylindrical hub 232 includes or defines a drive bearing (not shown). The drive shaft 228 is drivingly engaged to the cylindrical hub 232, and the drive bearing transmits rotational motion from the drive shaft 228 to the orbiting scroll 216.

[0040] The main bearing housing 234 is positioned within the outer shell 204 and is fixed relative to the compressor housing 202 (e.g., by press-fitting within the outer shell 204 or by other suitable fixation means). The fixed scroll 214 is connected to the main bearing housing 234. Additionally or alternatively, the fixed scroll 214 is connected to the partition 222. The main bearing housing 234 receives a bearing assembly (not shown) and cooperates with the bearing assembly to support rotational motion of the drive shaft 228 relative to the main bearing housing 234. The main bearing housing 234 also receives the cylindrical hub 232 of the orbiting scroll 216. The main bearing housing 234 includes a thrust surface that supports the cylindrical hub 232 and, more particularly, provides axial support for whirling motion of the orbiting scroll 216 relative to the main bearing housing 234, with the drive bearing positioned interior to the cylindrical hub 232. A coupler (not shown), such as a Oldham's coupler, engages the orbiting scroll 216 and the fixed scroll 214 or the main bearing housing 234 to prevent relative rotation therebetween.

[0041] An inlet fitting 236 is positioned on the compressor housing 202 and defines an inlet 238 for drawing working fluid into a fluid chamber defined by the scroll members 214, 216, where the working fluid is compressed. In the example compressor 200, the inlet fitting 236 is positioned on the outer shell 204 and connects the inlet 238 to the first chamber 208. After the working fluid is compressed, the compressed working fluid exits the compression stage 212 through the discharge passage 230 and enters the second chamber 220 at a discharge pressure. The compressed working fluid exits the second chamber 220 through a discharge outlet 242 defined by a discharge fitting 240. The discharge fitting 240 is attached to the end cover 206 of the compressor housing 202. In some examples, a discharge valve assembly (not shown) is positioned within the discharge fitting 240 and prevents or guards against reverse flow conditions through the discharge fitting 240.

[0042] Referring again to Figure 1 In operation of the vapor compression system 100, working fluid in the circuit 110 is compressed at the compression stage 120 of the compressor 106, which increases the pressure of the working fluid. Upstream of the compressor 106, the working fluid flows toward the compressor 106 via the line 122. The working fluid in the line 122 is at a low pressure and is substantially in a vapor phase, having been heated by the first heat exchanger 102. Some of the working fluid entering the compression stage 120 is in a liquid phase, and more particularly in the form of atomized droplets of liquid phase working fluid, to limit or even prevent an increase in temperature superheat experienced across the compression stage 120 as described below. The pressurized working fluid exits the compressor 106 and is conveyed toward the second heat exchanger 104 via the line 124, where the working fluid is condensed to a high pressure, substantially liquid phase state. The working fluid exiting the second heat exchanger 104 is conveyed toward the expansion device 108 via the line 126, which reduces the pressure of the working fluid. The working fluid, which is a mixture of vapor and liquid phases, exiting the expansion device 108 is conveyed toward the first heat exchanger 102 via the line 128. The working fluid is heated and substantially vaporized to a vapor phase in the first heat exchanger 102. The working fluid is then conveyed back to the compressor 106 via the line 122, where the working fluid is again compressed, and the process is repeated. Circulation of the working fluid in the circuit 110 is driven by the compressor 106, and optionally by one or more additional fluid displacement devices (e.g., pumps). As Figure 1As shown, in some examples, the flow direction of the working fluid through the circuit 110 is reversible to switch the heat transfer function of the first and second heat exchangers 102, 104 and enable the vapor compression system 100 to operate in various modes of operation. To enable the working fluid to flow in reverse in the circuit 110, in some examples, the vapor compression system 100 includes one or more reversing valves or four-way valves.

[0043] As Figure 1 shown, the vapor compression system 100 also includes an atomizer 138 connected to a source 140 of liquid phase working fluid and operable to introduce atomized or micron-sized droplets of the liquid phase working fluid into the vapor phase working fluid being delivered to the compression stage 120 of the compressor 106. The atomized droplets transfer heat from the vapor phase of the working fluid across the compression stage 120 as the atomized droplets evaporate during compression, extracting heat through the heat of evaporation. As described below, the atomizer 138 and source 140 are operated and controlled to use the heat of evaporation of the droplets to reduce heat generation across the compression stage 120 and improve compressor efficiency, reduce opportunities for compressor surging, and reduce the load on the compressor and energy consumption. The atomizer 138 and source 140 are also operated and controlled such that the atomized liquid phase droplets also reduce compressor noise while limiting or preventing the risk of liquid slugging occurring at the compressor 106. Liquid slugging occurs when liquid phase working fluid accumulates at or near the inlet of the compression stage 120 (i.e., at the suction side of the compressor 106) and strains the compressor 106 and can cause compressor damage or failure.

[0044] The atomizer 138 is positioned for introducing the droplets upstream of the compression stage 120. As Figure 1 shown, the atomizer 138 is positioned for introducing the droplets into the line 122. Alternatively, the atomizer 138 is located anywhere in the vapor compression system 100 to enable the atomizer 138 to function as described. In some examples, the atomizer 138 is located in the first heat exchanger 102 or in the housing of the compressor 106 upstream of the compression stage 120. Referring to Figure 2 , the atomizer 138 is shown located within the first chamber 208 of the scroll compressor 200 and designated 244. The atomizer 138 / 244 at this location is operable to introduce atomized droplets of the liquid phase working fluid that have accumulated near the base 210 of the compressor housing 202.

[0045] A source 140 of liquid working fluid for use with atomizer 138 is part of loop 110 and is located at any suitable location on loop 110. In some examples, source 140 is a pool of liquid working fluid in one or both of heat exchanger 102 and heat exchanger 104. Additionally or alternatively, source 140 is a pool of liquid working fluid in a reservoir located on loop 110. Figure 3 An example reservoir 302 positioned between the first heat exchanger 102 and the compressor 106 and used as the source 140 is described. Additionally or alternatively, a reservoir (e.g., Figure 3 In some examples, the reservoir source 140 is a portion of the compressor 106 that is located upstream of the compression stage 120. For example, referring to Figure 2 In one embodiment, the reservoir source 140 is a region of the first chamber 208 of the scroll compressor housing 202 near the base 210 where the liquid-phase working fluid entering via the inlet 236 accumulates under the action of gravity upstream of the compression stage 212. In yet another example, the source 140 is a pool of liquid-phase working fluid that has settled in the pipeline 122 upstream of the compressor 106. Additionally or alternatively, the source 140 of liquid-phase working fluid is an external source separate from the circuit 110, such as an external source of liquid-phase working fluid for injecting the working fluid into the circuit 110.

[0046] The atomizer 138 includes any suitable mechanism for producing atomized droplets of the liquid-phase working fluid from the source 140. The atomized droplets are suitably micron-sized, for example, between about 1 micron (μm) and about 20 μm in size. The micron-sized droplets provide a relatively large heat and mass transfer surface area for transferring heat across the compression stage 120 via heat of evaporation. The relatively small size of the droplets also limits or even prevents liquid slugging that may be caused by the introduction of the liquid-phase working fluid in the vapor phase upstream from the compression stage 120. Larger-sized droplets, for example, droplets exceeding 100 μm, may tend to accumulate at the inlet of the compression stage 120, which may result in liquid slugging. Additionally or alternatively, the larger-sized droplets may not evaporate sufficiently during compression and / or may reduce the flow rate of the working fluid across the compression stage 120, which may negatively impact compressor efficiency.

[0047] The atomizer 138 includes one or more acoustic energy devices in direct contact with a volume of the liquid-phase working fluid. The acoustic energy devices operate to atomize droplets of the liquid-phase working fluid by generating acoustic energy (e.g., ultrasonic waves) and directly applying the acoustic energy on the volume of the liquid-phase working fluid. In some examples, the acoustic energy devices include ultrasonic transducers. Any number of acoustic energy devices (e.g., ultrasonic transducers) can be included in the atomizer 138, such as one, two, or more than two acoustic energy devices. The acoustic energy devices are positioned at any suitable location within the source 140 and in direct contact with the liquid-phase working fluid to enable the atomizer 138 to function as described. For example, the acoustic energy devices are positioned within a pool of the liquid-phase working fluid in the sump 302 in Figure 3 or within the first chamber 208 of the scroll compressor housing in Figure 2 Referring again to Figure 2 The atomizer 244 in this example is an ultrasonic transducer positioned near the base 210 of the compressor housing 202. The atomizer 244 applies ultrasonic waves to the liquid-phase working fluid accumulated in the first chamber 208 near the base 210, thereby creating atomized droplets of the liquid-phase working fluid and introducing the droplets into the vapor-phase working fluid entering the compression stage 212. In this example, the atomizer 244 provides the additional advantage of providing an economical and efficient method to separate the liquid-phase working fluid from oil or other lubricants accumulated in the first chamber 208 near the base 210 and reintroduce such working fluid into the vapor phase and the compression stage 212.

[0048] In alternative examples, the atomizer 138 includes a nozzle, such as a spray nozzle, a swirl nozzle, or an ultrasonic nozzle, that operates to create atomized droplets of the liquid-phase working fluid delivered from the source 140 to the nozzle. The atomizer 138 implemented as a nozzle is used in combination with the source 140 of the liquid-phase working fluid that is remote from the atomizer 138. For example, the source 140 is a pool of the liquid-phase working fluid within the first heat exchanger 102, the second heat exchanger 104, a remote sump, or an external source, and the nozzle / atomizer 138 is located on the line 122 or within the compressor 106 upstream of the compression stage 120. In these examples, a pump or other displacement device is used to deliver the liquid-phase working fluid from the source 140 to the atomizer 138.

[0049] In example operation of vapor compression system 100, atomizer 138 generates droplets of liquid-phase working fluid and introduces the droplets into vapor-phase working fluid upstream of compression stage 120 (e.g., into line 122 and / or into compressor 106 upstream of compression stage 120). The droplets are carried by the vapor-phase flow through compression stage 120 and vaporize during compression to facilitate heat transfer and reduce temperature superheat of the compressed working fluid. In some examples, the droplets facilitate a substantially isothermal compression process whereby the working fluid experiences a temperature change across compression stage 120 that is within + / - 5°C of the saturation vapor temperature, such as within + / - 1°C of the saturation vapor temperature.

[0050] Controller 134 controls atomizer 138 to adjust (e.g., increase or decrease) the amount of droplets introduced into the vapor phase based on one or more monitored conditions of the working fluid in circuit 110. The monitored conditions are provided as inputs to controller 134 from one or more sensors (e.g., sensors 130, 132) of vapor compression system 100. Example control algorithms implemented by controller 134 to control atomizer 138 are described in detail below. In various examples, controller 134 causes atomizer 138 to increase or decrease the amount of droplets introduced into the vapor phase to control the discharge temperature of the working fluid exiting compression stage 120, the volumetric ratio of compressor 106 (e.g., scroll compressor 200), and / or the concentration of the working fluid (e.g., in the case that the working fluid includes a mixture of two or more refrigerants having different boiling points).

[0051] In examples where atomizer 138 (e.g., an ultrasonic transducer) is in direct contact with the liquid-phase working fluid in source 140 (e.g., a reservoir), controller 134 controls the amount of droplets introduced into the vapor phase by adjusting the amount of energy (e.g., ultrasonic waves) applied by atomizer 138 on the liquid phase. For example, controller 134 adjusts the operating frequency of the ultrasonic transducer to generate more or fewer atomized droplets that are introduced into the vapor-phase working fluid.

[0052] In examples where source 140 of liquid-phase working fluid is remote from atomizer 138 (e.g., a nozzle), controller 134 controls the amount of droplets introduced into the vapor phase by adjusting the flow rate of the liquid phase supplied from source 140 to atomizer 138. For example, the amount of liquid-phase working fluid supplied from source 140 to atomizer 138, and thus the amount of droplets introduced into the vapor-phase working fluid that is delivered to compression stage 120, is controlled by adjusting the speed of a pump that supplies the liquid phase from source 140 to atomizer 138. Alternatively, in some examples, a flow metering valve or another flow control device is used to adjust the amount of liquid-phase working fluid supplied to atomizer 138.

[0053] Referring now toFigure 3 , shows another example vapor compression system 300. The vapor compression system 300 includes Figure 1 The vapor compression system 100 corresponds to the elements and components of the vapor compression system 100, and the elements and components are indicated using corresponding reference numerals. The vapor compression system 300 also includes a reservoir 302 (indicated by 320 in this example) provided on the working fluid circuit. The reservoir 302 operates as a source 140 of liquid working fluid and an atomizer 138 as described below. The reservoir 302 is positioned between the first heat exchanger 102 and the compressor 106 and contains two different phases of working fluid - a liquid phase 304 and a vapor phase 306. The reservoir 302 is a vapor-liquid separation vessel (e.g., a flash tank, a cyclone separator, a cold trap, etc.) that separates the liquid phase 304 and the vapor phase 306. The vapor compression system 300 in this example also includes a condensed working fluid receiver 312 and a liquid suction heat exchanger 314 located upstream of the receiver 312. The receiver 312 is a tank or container that stores or holds a certain volume of condensed working fluid upstream of the expansion device 108. In some examples, a control valve (not shown) is positioned upstream of the receiver 312 to limit or prevent backflow of the working fluid. A filter dryer (not shown) can be positioned downstream of the receiver 312 and operated to remove contaminants (e.g., corrosive materials) from the working fluid. The liquid suction heat exchanger 314 receives the high-pressure working fluid from the second heat exchanger 104 along the first flow direction, and receives the low-pressure working fluid from the first heat exchanger 102 along the second flow direction to transfer heat between the low-pressure working fluid and the high-pressure working fluid upstream of the reservoir 302 and the receiver 312. The liquid suction heat exchanger 314 includes any suitable heat exchanger design, including the designs described above for the first heat exchanger 102 and the second heat exchanger 104.

[0054] like Figure 3 As shown, the liquid phase 304 collects in the interior volume of the reservoir 302 near the bottom, and the vapor phase 306 within the interior volume is near the top of the reservoir 302, above the liquid phase 304. The vapor phase 306 is conveyed from the reservoir 302 toward the compression stage 120 via line 308. Some of the liquid phase 304 in the reservoir 302 is atomized into droplets using the reservoir 302, and the droplets are introduced into the vapor phase 306 exiting the reservoir 302. The droplets of liquid phase 304 are introduced into the vapor phase 306 to provide the advantages described above, such as, among other things, facilitating heat transfer during compression, reducing temperature superheat of the compressed working fluid, and improving compressor efficiency. Figure 4 and Figure 5 An example of atomizing the liquid phase 304 using the reservoir 302 is described.

[0055] In operation of the vapor compression system 300, working fluid is delivered from the reservoir 302 to the compressor 106 via the line 308 and includes both the vapor phase 306 and droplets of the liquid phase 304 introduced by the reservoir 302. The working fluid is compressed at the compression stage 120 of the compressor 106, which increases the pressure of the working fluid. Atomized droplets of the liquid phase 306 suitably limit or even prevent an increase in the temperature of the working fluid from superheat to improve compressor efficiency. The pressurized working fluid exits the compressor 106 and is delivered via the line 316 toward the second heat exchanger 104, where the working fluid is condensed to a high pressure, substantially liquid phase state. The working fluid exiting the second heat exchanger 104 is delivered via the line 318 toward the liquid suction heat exchanger 314, where the high pressure working fluid transfers heat with the low pressure working fluid from the first heat exchanger 102. The high pressure working fluid and the low pressure working fluid exit the liquid suction heat exchanger 314 via the lines 322, 324, respectively. The high pressure working fluid exiting the liquid suction heat exchanger 314 is delivered via the line 322 toward the receiver 312, and the low pressure working fluid is delivered via the line 324 toward the reservoir 302. The flow of the liquid phase 304 and the vapor phase 306 of the working fluid in the line 324 separate in the reservoir 302, which also operates to atomize some of the liquid phase 304 into droplets and introduce the droplets into the vapor phase 306, which is drawn through the line 308 toward the compression stage 120. The high pressure working fluid is temporarily housed in the receiver 312 before being delivered via the line 326 toward the expansion device 108.

[0056] The liquid-suction heat exchanger 314 operates to transfer heat between the relatively higher temperature liquid working fluid exiting the second heat exchanger 104 and the relatively lower temperature two-phase working fluid exiting the first heat exchanger 102. For example, by allowing for incomplete evaporation at the first heat exchanger 102 and / or incomplete condensation at the second heat exchanger 104, such intermediate cooling reduces power consumption and / or otherwise improves performance of the first heat exchanger 102 and / or the second heat exchanger 104. For example, the relatively higher temperature liquid working fluid in the line 318 increases the temperature and vapor quality of the working fluid from the first heat exchanger 102 in the line 330, while providing a higher subcooling level or lower temperature and lower vapor quality of the liquid working fluid in the line 318. Thus, the liquid-suction heat exchanger 314 provides certain advantages in the vapor compression system 300, including further cooling of the liquid working fluid before it enters the expansion device 108, which can improve system efficiency, can reduce flashing that can occur in the liquid line, and enable the expansion device 108 to operate with greater stability. In this way, the partially evaporated working fluid is further evaporated by heat transfer with slightly warmer, partially condensed (or supercooled) working fluid from the same cycle. In some examples, the liquid-suction heat exchanger 314 also enables the first heat exchanger 102 to evaporate working fluid without over-heating, which can improve performance of the compressor 106.

[0057] The working fluid exiting the expansion device 108 is conveyed via the line 328 toward the first heat exchanger 102, where the working fluid is heated in the first heat exchanger and then conveyed via the line 330 to the liquid-suction heat exchanger 314. As described above with respect to the system 100, in some examples, the flow direction of the working fluid through the circuit 320 is reversible to switch the heat transfer functions of the first heat exchanger 102 and the second heat exchanger 104 and enable the vapor compression system 300 to operate in various modes of operation.

[0058] The vapor compression system 300 can operate using a "high glide" refrigerant blend as a working fluid. A high glide refrigerant blend includes a first refrigerant and a second refrigerant, where the difference between the boiling point of the first refrigerant and the boiling point of the second refrigerant is greater than or equal to 25 °C. In certain examples, the vapor compression system 300 can operate using a high glide refrigerant blend, where the first refrigerant and the second refrigerant are independently selected from the group consisting of carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1,1,2-tetrafluoroethane (R134A), R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125)), 1,1-difluoroethane (R152a), dimethyl ether (R-E170), propane (R-290), 2,3,3,3-tetrafluoroprop-l-ene (R-1234yf), cis and trans- 1,3,3,3-tetrafluoropropene (HFO-1234ye), cis and trans- 1,3,3,3-tetrafluoroprop-l-ene (R-1234ze), 3,3,3-trifluoropropene (HFO-1234zf), trifluoromonochloropropene (HFO-1233), trans- 1-chloro-3,3,3-trifluoropropene (HFO-1233zd(E)), cis- 1-chloro-3,3,3-trifluoropropene (HFO-1233zd(Z)), 2-chloro-3,3,3-trifluoropropene (HFO-1233xf), trans- 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(Z)), cis- 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(E)), pentafluoropropene (HFO-1225), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,2,3,3,3-pentafluoropropene (HFO-1225yez), hexafluorobutene (HFO-1336), cis- 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(Z)), trans- 1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)), trans- 1,2-difluoroethylene (R-1132(E)), and any isomers or combinations thereof. Although the refrigerant blend can be described herein as including a first refrigerant blend and a second refrigerant blend, the refrigerant blend includes more than two refrigerants in some examples.

[0059] One or more components of vapor compression system 300 (e.g., liquid suction heat exchanger 314 and accumulator 302) enable the use of a high glide refrigerant blend by allowing the refrigerant blend to undergo partial phase changes at the evaporation stage (e.g., first heat exchanger 102) and condensation stage (e.g., second heat exchanger 104) of vapor compression system 300 and change the relative proportion of the first and second refrigerants in the working fluid blend at different points in system 300. For example, a substantial proportion of the liquid phase 304 in accumulator 302 is the one of the first and second refrigerants that has a higher boiling point, while a substantial proportion of the vapor phase 306 in accumulator 302 is the one of the first and second refrigerants that has a lower boiling point. Accumulator 302 operates to change the proportion of the first and second refrigerants in the blend by introducing droplets of the liquid phase 304 into the vapor phase 306 without negatively impacting the performance and efficiency of compressor 106. In some examples, additional components are included and implemented to enable the use of such a high glide refrigerant blend, such as those described in Welch et al. U.S. Pub. No. 2023 / 0130167, the entire disclosure of which is incorporated by reference herein. For example, in system 300, one or more additional accumulators (e.g., receiver 312) are included at any suitable location on circuit 320. In this way, the final density of the compressor suction (upstream of compression stage 120) is altered by preferentially storing and introducing a concentrated amount of the first or second refrigerant in one or more selected regions of the system. In some such examples, one or more of the additional accumulators function as described for accumulator 302 by preferentially introducing liquid phase droplets of the first or second refrigerant to change the concentration of the working fluid blend at the respective location.

[0060] Referring now to Figure 4 An example of accumulator 302 used in system 300 is schematically illustrated and indicated with 400. In some examples, accumulator 400 is included in vapor compression system 100 Figure 1), such as included in line 122 upstream of compression stage 120. Accumulator 400 operates as a flash tank or other vapor-liquid separation vessel and includes a body 402 defining an interior volume 404 in which a liquid phase 406 of the working fluid is separated from a vapor phase 408 of the working fluid. In this example, body 402 is cylindrical in shape, but may have any suitable shape to enable accumulator 400 to function as described. In some examples, as described above, the working fluid is a refrigerant blend including a first refrigerant and a second refrigerant, wherein the difference between the boiling point of the first refrigerant and the boiling point of the second refrigerant is greater than or equal to 25°C. In these examples, a substantial proportion of liquid phase 406 is the one with the higher boiling point of the first refrigerant and the second refrigerant, while a substantial proportion of vapor phase 408 is the one with the lower boiling point of the first refrigerant and the second refrigerant. Alternatively, the working fluid includes a single refrigerant in a two-phase state, and the two phases separate into liquid phase 406 and vapor phase 408. The two-phase state is a result of partial or incomplete evaporation at the first heat exchanger 102 and / or the introduction of a liquid phase 406 into the working fluid at or upstream of the reservoir 400 for economization of the vapor compression system 100 / 300. In some examples, the liquid phase 406 also includes lubricating oil present in the working fluid. In some such examples, the collection of the liquid phase 406 in the reservoir limits or even prevents the compression stage 120 ( Figure 1 and Figure 3 ). Additional non-limiting advantages of the accumulator 400 include, for example, storing an additional charge of working fluid to compensate for operational variations of the vapor compression system 100 / 300 (e.g., variations in field piping length and / or variations in operating mode), and controlling oil return to the compressor 106.

[0061] The working fluid enters the interior volume 404 via an inlet 412 defined by an inlet fitting 414 positioned on the body 402. The inlet fitting 414 is located on the sidewall 416 of the body 402 near the top 424 of the body 402, but may be located elsewhere on the body 402. Figure 5In the example shown and described below, the inlet fitting 414 is positioned proximate to the bottom 426 of the body 402. The liquid phase 406 is deposited proximate to the bottom 426 of the body 402, forming a pool 410 in the interior volume 404. The vapor phase 408 is located above the surface 418 of the pool 410 in the interior volume 404 and is transported to the outlet 422 of the body 402 through an internal conduit 420. The outlet 422 is defined by an outlet fitting 436 positioned on the sidewall 416 of the body 402 proximate to the top 424 and diametrically opposed to the inlet fitting 414. In other examples, the outlet fitting 436 is positioned at other locations on the body 402. In this example, the internal conduit 420 is U-shaped, defining a conduit inlet 428 located above the surface 418 of the pool 410. The internal conduit 420 can have any suitable shape to function as described. The conduit inlet 428 is positioned to receive the vapor phase 408 without receiving a volume of the liquid phase 406 in the pool 410. As Figure 4 shown, the conduit 420 initially extends downward from the conduit inlet 428 into the pool 410 and turns to extend upward and ultimately connects to the outlet 422 of the body 402. The conduit 420 operates to control the phase proportion of the working fluid that is transported to the compressor 106. In some examples, the conduit 420 is omitted.

[0062] The reservoir 400 also includes an atomizer 430 (labeled 430a-430e in Figure 4 FIG. 4B) positioned and operable to atomize the liquid phase 406 into atomized or micron-sized droplets 432 and introduce the droplets 432 into the vapor phase 408. The droplets 432 are sized (e.g., between about 1 pm and about 20 pm in size) such that the vapor phase 408 carries the droplets 432 to the internal conduit 420 and toward the compressor 106, where the droplets 432 operate to transfer heat across the compression stage 120 as described above. Larger-sized droplets 434 (e.g., greater than about 100 pm in size) are not suitable for being carried by the vapor phase 408 and instead fall into the pool 410 due to their terminal velocity. Thus, the larger-sized droplets 434 are prevented from flowing toward the compressor 106, which is advantageous because these larger-sized droplets 434 can not fully vaporize across the compression stage 120 and / or can cause liquid slugging.

[0063] In the example reservoir 400, the atomizer 430 is an ultrasonic transducer that directly contacts the liquid phase 406 of the working fluid. The ultrasonic transducer 430 operates by generating ultrasonic waves and applying ultrasonic energy directly on the liquid phase 406, thereby creating atomized droplets 432. The reservoir 400 can include any number of ultrasonic transducers 430, such as one, two, or more than two ultrasonic transducers (e.g., three, four, five, six, seven, eight, nine, ten, or more than ten ultrasonic transducers). The position of the ultrasonic transducer 430 in this example is described below. In other examples, the ultrasonic transducer is in any suitable position to function as described. In some examples, one or more ultrasonic transducers 430 are positioned on a line upstream of the reservoir 400 (e.g., line 326 in Figure 3 and / or on a line downstream of the reservoir (e.g., line 308 in Figure 3 ). In the vapor compression system 100 of Figure 1 , the reservoir 400 can be on line 122, and one or more ultrasonic transducers 430 can be positioned on line 122 upstream and / or downstream of the reservoir 400.

[0064] As shown in Figure 4 , in this example, five ultrasonic transducers 430 are included in the reservoir 400 (labeled 430a-430e). The first ultrasonic transducer 430a is positioned within the inlet fitting 414 in a manner proximate to the inlet 412. The second ultrasonic transducer 430b is positioned on the inner surface of the sidewall 416 in a manner proximate to the surface 418 of the pool 410. The remaining three ultrasonic transducers 430c-430e are positioned within the internal conduit 420. In particular, the third ultrasonic transducer 430c is positioned along the downwardly extending portion of the conduit 420, the fourth ultrasonic transducer 430d is positioned proximate to the bottom turn of the conduit 420, and the fifth ultrasonic transducer 430e is positioned along the upwardly extending portion of the conduit 420. In some examples, the ultrasonic transducers 430 are additionally or alternatively positioned within the outlet fitting 436.

[0065] In operation of the reservoir 400, the working fluid enters the internal volume 404 via the inlet 412 as indicated by flow line 440. The working fluid 440 at this stage is a two-phase mixture of the vapor phase 408 and the liquid phase 406. The working fluid 440 is received from the first heat exchanger 102 (e.g., an evaporator) of Figure 1 and / or Figure 3 and / or from the second heat exchanger 104 (e.g., a condenser) of Figure 3The first ultrasonic transducer 430a positioned in the inlet fitting 414 operates to generate droplets 432 before the working fluid 440 enters the internal volume 404. As the working fluid 440 enters the internal volume 404, the non-atomized liquid phase 406 and larger sized droplets 434 collect in the pool 410, and the atomized droplets 432 remain within the vapor phase 408 and are carried to the conduit inlet 428 of the internal conduit 420. The second ultrasonic transducer 430b operates to generate atomized droplets 432 from the pool 410 proximate the surface 418, and these droplets 432 are also carried by the vapor phase 408 toward the conduit inlet 428. The vapor phase 408 and atomized droplets 432 are transported through the internal conduit 420 toward the outlet 422. The ultrasonic transducers 430c-430e in the conduit 420 operate to generate droplets 432 within the conduit 420 and / or to maintain the atomized size of the droplets 432 passing through the conduit 420 to prevent the liquid phase 406 from collecting and depositing in the conduit. The vapor phase 408 and atomized droplets 432 are then transported out of the reservoir 400 via the outlet 422 and toward the compression stage 120 of the compressor 106 as indicated by the flow arrow 442. Again, in some examples, ultrasonic transducers are also positioned in the outlet fitting 436 and operate to generate droplets 432 proximate the outlet 422 and / or to prevent the liquid phase 406 from collecting and depositing in the outlet.

[0066] Figure 5 is another example of a reservoir 302 used in the system 300, which is shown schematically and indicated at 500. The reservoir 500 is similar to the reservoir 400 described above with reference to FIGS. 4-6 and corresponding reference numerals are used to indicate corresponding elements and components. As with the reservoir 400, the reservoir 500 can also be used in the vapor compression system 100 and operate as a flash tank or other vapor-liquid separation vessel. Unless otherwise explicitly stated or otherwise clearly indicated by context, the above description of the reservoir 400 applies equally to the reservoir 500. From the reservoir 500, the working fluid 440 is supplied to the liquid-suction heat exchanger 314 of the compressor 106. The first ultrasonic transducer 430a positioned in the inlet fitting 414 operates to generate droplets 432 before the working fluid 440 enters the internal volume 404. As the working fluid 440 enters the internal volume 404, the non-atomized liquid phase 406 and larger sized droplets 434 collect in the pool 410, and the atomized droplets 432 remain within the vapor phase 408 and are carried to the conduit inlet 428 of the internal conduit 420. The second ultrasonic transducer 430b operates to generate atomized droplets 432 from the pool 410 proximate the surface 418, and these droplets 432 are also carried by the vapor phase 408 toward the conduit inlet 428. The vapor phase 408 and atomized droplets 432 are transported through the internal conduit 420 toward the outlet 422. The ultrasonic transducers 430c-430e in the conduit 420 operate to generate droplets 432 within the conduit 420 and / or to maintain the atomized size of the droplets 432 passing through the conduit 420 to prevent the liquid phase 406 from collecting and depositing in the conduit. The vapor phase 408 and atomized droplets 432 are then transported out of the reservoir 500 via the outlet 422 and toward the compression stage 120 of the compressor 106 as indicated by the flow arrow 442. Again, in some examples, ultrasonic transducers are also positioned in the outlet fitting 436 and operate to generate droplets 432 proximate the outlet 422 and / or to prevent the liquid phase 406 from collecting and depositing in the outlet. Figure 4 Figure 1 Figure 5 The atomizer 430 is omitted from the reservoir 500, but the reservoir 500 can also include the atomizer 430 and the above description of the atomizer 430 applies equally to the reservoir 500.

[0067] In the example reservoir 500, the inlet fitting 414 is positioned proximate the bottom 426 of the body 402, and the outlet fitting 436 is positioned proximate the top 424 and diametrically opposite the inlet fitting 414. The relative positioning of the inlet fitting 414 and the outlet fitting 436 results in the vapor phase 408 flowing generally upward in the internal volume 404 between the inlet 412 and the outlet 422. The inlet fitting 414 is also positioned such that the inlet 412 is at least partially below the surface 418 of the pool 410 of the liquid phase 406.​​

[0068] In an example operation of the reservoir 500, a working fluid 440 enters the interior volume 404 via the inlet 412. The working fluid 440 flows through the reservoir 410, and the vapor phase 408 generally flows upward across the surface 418 toward the conduit inlet 428, while the liquid phase 406 is at least partially collected in the reservoir 410. The velocity of the working fluid 442 drives some of the liquid phase 406 out of the reservoir 410 along with the vapor phase 408, thereby producing atomized droplets 432 and larger droplets 434 above the surface 418. Due to the difference in terminal velocities of the atomized (smaller) droplets 432 and the larger droplets 434, the droplets 432, 434 separate, with the atomized droplets 432 being carried by the vapor phase 408 to the conduit inlet 428 and the larger droplets 434 falling or depositing back into the reservoir 410. The conduit inlet 428 is located at an appropriate height H1 above the surface 418 of the pool 410 to allow the droplets 432, 434 to separate by their terminal velocity. The vapor phase 408 and the atomized droplets 432 are conveyed through the internal conduit 420 toward the outlet 422. The vapor phase 408 and the atomized droplets 432 are then conveyed out of the reservoir 400 via the outlet 422 and toward the compression stage 120 of the compressor 106, as indicated by the flow line 442. Here again, in some examples, one or more ultrasonic transducers (e.g., ultrasonic transducers 430a to 430e) are included in the reservoir 500 and positioned as described above with reference to Figure 4 The reservoir 400 operates as described.

[0069] Figure 6 It is a steam compression system, such as Figure 1 The vapor compression system 100 and / or Figure 3 An example of a method 600 for operating the vapor compression system 300 is provided. The method 600 includes compressing 602 a working fluid at a compression stage of a compressor (e.g., compression stage 120 of compressor 106). The method 600 also includes cooling 604 the working fluid at a condenser downstream of the compressor (e.g., second heat exchanger 104) and heating 606 the working fluid at an evaporator downstream of the condenser (e.g., first heat exchanger 102). In some examples of the method 600, an expansion device (e.g., expansion device 108) is used to expand or decompress the working fluid between the condenser and the evaporator.

[0070] The method 600 also includes conveying 608 the vapor phase of the working fluid from the evaporator toward the compressor. In some examples, the vapor phase is separated from the liquid phase of the working fluid within an internal volume of a reservoir (e.g., reservoirs 302, 400, 500) downstream of the evaporator and upstream of the compression stage. Alternatively, the working fluid is substantially entirely in the vapor phase exiting the evaporator, and the liquid phase may originate from another source (e.g., as described above with reference to FIG. Figure 1 The liquid phase is partially atomized 610 (e.g., using atomizers 138, 430 and / or reservoirs 400, 500) and droplets of the atomized liquid phase are introduced into the vapor phase being transported toward the compression stage. In some examples of method 600, atomizing 610 the liquid phase of the working fluid into droplets includes contacting the liquid phase with an ultrasonic transducer (e.g., ultrasonic transducer 430) positioned in the interior volume of the reservoir. Alternatively, the ultrasonic transducer may be positioned along a line upstream of the compression stage (e.g., Figure 1 Line 122 or Figure 3 In some examples of method 600, atomizing 610 the liquid phase into droplets includes flowing the vapor phase of the working fluid generally upward within the interior volume of the reservoir, such that the vapor phase carries relatively small liquid phase droplets, while relatively larger liquid phase droplets separate from the vapor phase and accumulate within the interior volume. As the atomized droplets introduced into the vapor phase are conveyed toward the compression stage, method 600 also includes transferring heat during compression via heat of vaporization of the droplets of the liquid phase introduced into the vapor phase.

[0071] Method 600 also includes controlling 612 the amount of liquid phase droplets introduced into the vapor phase based on one or more characteristics of a working fluid in the vapor compression system. The one or more characteristics of the working fluid indicate the operating performance and / or efficiency of the vapor compression system. For example, the one or more characteristics of the working fluid include the temperature superheat of the working fluid exiting the compressor, the volume ratio of the compressor, the relative concentration or ratio of the working fluid at different stages of the vapor compression system (e.g., when the working fluid includes a high-glide refrigerant blend), and any one or more of other characteristics. The characteristics of the working fluid are determined using a controller (e.g., controller 134) by monitoring conditions (e.g., temperature and / or pressure) at one or more stages of the vapor compression system. For example, the vapor compression system includes sensors (e.g., sensors 130, 132) positioned to monitor conditions (e.g., temperature and / or pressure) of the working fluid upstream and downstream of one, some, or each working component of the vapor compression system (e.g., evaporator, condenser, compressor, expansion device, accumulator, and other components). In some examples of the method, the controller receives information related to monitored conditions of the vapor compression system at two or more stages, determines one or more characteristics of the working fluid at each stage based on the monitored information, compares the characteristics at different stages, and controls the amount of liquid phase droplets introduced into the vapor phase based on the comparison 612. Figures 7 to 10 An example control scheme that may be implemented in method 600 is described.

[0072] Controlling 612 the amount of liquid phase droplets introduced into the vapor phase includes increasing or decreasing the amount of droplets introduced. The manner in which the amount of liquid phase droplets introduced into the vapor phase is controlled 612 varies depending on the manner in which the droplets are atomized 610 and introduced into the vapor phase. For example, the amount of droplets introduced into the vapor phase may be controlled 612 by controlling the flow rate of the liquid phase supplied to the atomizer from a remote liquid refrigerant source (e.g., as described with reference to FIG. 1 ). Figure 1 Alternatively, the amount of liquid droplets introduced into the vapor phase at 612 is controlled by adjusting the amount of energy (e.g., ultrasonic waves) applied to the liquid phase by an atomizer in direct contact with the liquid phase (e.g., by adjusting the operating frequency of an ultrasonic transducer used to atomize the liquid phase). Depending on the specific configuration of the vapor compression system and atomizer used, any suitable means may be used to control the amount of liquid droplets introduced into the vapor phase at 612.

[0073] Figure 7 In the vapor compression system (e.g. Figure 1 The vapor compression system 100 and / or Figure 3An example block diagram of a controller 134 used in a vapor compression system 300) is shown in FIG. 8. The controller 134 is a computer system that includes at least one processor 706 and at least one memory device 708. The memory device 708 includes a non-transitory computer readable medium and a program that is accessed by the processor 706 and is executable to implement the functionality described for the controller 134. The controller 134 receives inputs 702 that include monitored conditions of the vapor compression system. For example, the inputs 702 include monitored temperature and pressure information from one or more stages of the vapor compression. In some examples, the inputs 702 include monitored conditions (e.g., temperature and / or pressure) received from two or more stages of the vapor compression system. The monitored conditions are measured or detected using appropriately positioned sensors (e.g., sensors 130, 132 in FIGS. 1 Figure 1 and Figure 3 The controller 134 is operable to process the inputs 702 using one or more control algorithms and generate outputs 704 for controlling the amount of liquid phase droplets introduced into the vapor phase delivered to the compressor 106 as described above. The outputs 704 are generated continuously, periodically, or intermittently. The controller 134 executes one or more control algorithms (e.g., stored in the memory device 708) to determine one or more properties of the working fluid based on the inputs 702 and generate the outputs 704 based on the one or more properties of the working fluid determined using the inputs 702. The properties of the working fluid are determined based on the inputs 702 related to the monitored conditions of a single stage or multiple stages of the vapor compression system. Depending on the control algorithm employed, the controller 134 controls the amount of liquid phase droplets introduced into the vapor phase based on the properties of the working fluid determined at a single stage or multiple stages.

[0074] Figure 8 is one example of a control algorithm 800 implemented by the controller 134. In this example, the control algorithm 800 is implemented to control the amount of liquid phase droplets introduced into the vapor phase delivered toward the compression stage based on a monitored temperature at the discharge of the compression stage 120 or a compressor discharge temperature (i.e., the temperature of the compressed working fluid at the outlet of the compressor). A sensor (e.g., sensor 130 in FIG. 1) positioned downstream of the compression stage 120 is used to measure the compressor discharge temperature. The compressor discharge temperature is monitored and used by the controller 134 to determine the amount of liquid phase droplets to introduce into the vapor phase delivered toward the compression stage 120. Figure 1 and Figure 3Sensor 132 in the compressor 134 monitors the compressor discharge temperature. At operation 802, the compressor discharge temperature is received as input 702 by controller 134, and at operation 804, controller 134 determines the temperature superheat of the compressed working fluid based on input 702. In this example, the compressor discharge temperature is the monitored condition, while the temperature superheat is the determined characteristic of the working fluid. At operation 806, controller 134 also compares the temperature superheat to a compressor protection limit, which is determined empirically or based on simulated operating cycles of the vapor compression system. If the temperature superheat is above the compressor protection limit, this indicates that more atomizing liquid should be introduced to increase heat transfer across the compression stages, thereby reducing the temperature superheat of the compressed working fluid. In response to this determination at operation 806, controller 134 generates output 704 at operation 808, causing more liquid-phase working fluid to be atomized and introduced into the vapor phase. If the temperature superheat is below the compressor protection limit, this indicates that less atomizing liquid should be introduced, as the reduction in temperature superheat is more than sufficient to meet system requirements. In response to this determination at operation 806 , at operation 810 , the controller 134 generates an output 704 causing less of the liquid-phase working fluid to be atomized and introduced into the vapor phase.

[0075] Figure 9 is another example of a control algorithm 900 implemented by the controller 134. In this example, the control algorithm 900 is implemented to control the amount of liquid phase droplets introduced into the vapor phase being transported toward the compression stage based on the monitored temperatures and pressures at the discharge and suction of the compression stage 120, i.e., based on the compressor discharge temperature and pressure and the compressor suction temperature and pressure. Using one or more sensors located downstream of the compression stage 120 (e.g., Figure 1 and Figure 3 The compressor discharge temperature and pressure are monitored using one or more sensors located upstream of the compression stage 120 (e.g., sensor 132 in FIG. Figure 1 and Figure 3 The sensor 130 in the compressor monitors the compressor suction temperature and pressure. At operation 902, these temperatures and pressures are received as input 702 by the controller 134, and at operation 904, the controller 134 determines the density of the working fluid at each stage (i.e., the density at the compressor suction port p 吸入 and the density at the compressor discharge ρ 排放). In this example, the compressor discharge temperature and pressure and the suction temperature and pressure are the monitored conditions, and the working fluid density is the characteristic of the working fluid determined. The density of the working fluid at the compressor suction port and the compressor discharge port is used to measure the operating volume ratio of the compressor to the expected or required volume ratio. The volume ratio is a performance characteristic of certain types of compressors, such as scroll compressors and / or screw compressors. Therefore, in some examples of implementing the control algorithm 900, the compressor 106 is a scroll compressor 200 ( Figure 2 ).

[0076] To measure the volumetric performance of the compressor, the controller 134 compares the compressor suction density ρ at operation 906. 吸入 and compressor discharge density ρ 排放 , to determine the ratio ρ 排放 / ρ 吸入 Then, at operations 906 and 910, the ratio is compared to a predetermined range of values ​​indicative of an ideal volume ratio performance. 排放 / ρ 吸入 If the determined ratio ρ exceeds the predetermined upper limit, then at operation 908, the controller 134 generates output 704 to cause more liquid working fluid to be atomized and introduced into the vapor phase. 排放 / ρ 吸入 If the ratio is below the predetermined lower limit, then at operation 912, the controller 134 generates output 704 to cause less liquid working fluid to be atomized and introduced into the vapor phase. 排放 / ρ 吸入 Within the predetermined range, the controller 134 maintains the amount of liquid-phase working fluid currently being atomized and introduced into the vapor phase.

[0077] Figure 10 is another example of a control algorithm 1000 implemented by the controller 134. In this example, the control algorithm 1000 is implemented based on the monitored temperature (T c ) and the monitored temperature at the evaporator inlet (T e ) to control the amount of liquid phase droplets introduced into the vapor phase delivered to the compression stage. The control algorithm 1000 is suitable for examples where the working fluid is a high glide refrigerant blend and a partial phase change and separation occurs between the condenser and the evaporator (e.g., as described above with reference to Figure 3 Based on experience or simulation data, the function f(T c , T e) to estimate the relative proportion of refrigerant in the working fluid at each of the two stages (i.e., leaving the condenser and entering the evaporator). The controller 134 uses this equation to determine whether additional liquid-phase refrigerant should be added to the vapor phase to adjust the relative proportion of refrigerant in the working fluid entering the compression stage. The following Equation 1 is an example of a general equation that can be used in this control algorithm 1000 as a function f(T c , T e ) where the coefficients A, B, C, D, and E and the constant F are determined using empirical or simulated data for the vapor compression system:

[0078]

[0079] The temperatures T c and T e are monitored using one or more sensors located downstream of the condenser (e.g., the second heat exchanger 104) and upstream of the evaporator (e.g., the first heat exchanger 102), respectively. At operation 1002, these temperatures are received by the controller 134 as inputs 702, and at operation 1004, the controller 134 determines an output value using the function f(T c , T e ). The output value indicates the concentration or relative proportion of refrigerant in the working fluid blend, and at operations 1006, 1010, the output value is compared to a predetermined range of values that indicate the ideal proportion in the blend at the two stages being monitored. In this example, the temperatures T c , T e are the monitored conditions, and the output value determined using the function f(T c , T e ) is a determined characteristic of the working fluid. If the output value exceeds a predetermined upper value, then at operation 1008, the controller 134 generates an output 704 that causes more of the liquid-phase working fluid to be atomized and introduced into the vapor phase. If the output value is below a predetermined lower value, then at operation 1012, the controller 134 generates an output 704 that causes less of the liquid-phase working fluid to be atomized and introduced into the vapor phase. If the output value is within the predetermined range, as determined at operations 1006 and 1010, then the controller 134 maintains the amount of liquid-phase working fluid that is currently being atomized and introduced into the vapor phase.

[0080] The various examples of vapor compression systems and methods of operating and controlling these systems are described above. The advantages of the above-described systems and methods will be appreciated and understood by reading the entire disclosure. Non-limiting advantages and technical effects of the above-described systems and methods include: i) reducing lift of the vapor compression system; ii) providing for inter-cooling of the compressor to improve evaporator and / or condenser performance and reduce overall energy consumption; iii) reducing compressor noise without sacrificing compressor efficiency and / or increasing the propensity for compressor damage or failure (e.g., by liquid slugging); iv) enabling the use of high glide refrigerant blends while allowing for phase separation and reintroduction between the two refrigerants in the blend to control the refrigerant ratio; v) reducing the temperature superheat of the compressed working fluid exiting the compressor; vi) reducing the opportunity for damage to lubricants and / or mechanical components due to temperature superheat; vii) facilitating easier, faster, and more reliable liquid refrigerant injection mass flow into the compression stage; vii) allowing for efficient and reliable removal of refrigerant from the oil accumulation in the vapor compression system; viii) enabling the evaporator to operate in a flooded or near flooded condition to improve system capacity and efficiency; ix) providing a flash tank economizer that is capable of efficiently and reliably performing wet injection of liquid refrigerant without causing damage to the compressor or negatively impacting compressor efficiency; x) preventing liquid backflow in the compressor; xi) increasing the flow rate of the working fluid through the compression stage, thereby increasing the capacity of the compressor; xii) reducing the overall energy consumption of the vapor compression system; xiii) enabling the use of low global warming potential refrigerants; xiv) reducing the size of components (e.g., heat exchangers) and the overall footprint of the vapor compression system; and xv) enabling the above-described advantages i) through xiv) while reducing the complexity of the system.

[0081] Example implementations of the vapor compression system and method are described above. The system and method can be implemented in any application suitable for use with a vapor compression system. For example, the vapor compression system and method can be used in a climate control system (e.g., an HVAC system), a refrigeration system, and / or a heat pump. The system and method are not limited to the specific implementations described herein. Components of the system and method can be used independently and separately from other components described herein. For example, the atomizer and accumulator described herein can be used in any suitable vapor compression system.

[0082] When introducing elements of the present application or the embodiments thereof, the articles "a," "an," "the," and "said” are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there can be additional elements other than the listed elements.

[0083] Unless otherwise stated, approximate language such as "substantially", "substantially" and "approximately" as used herein indicates that the term so modified may apply only to an approximate degree, as will be appreciated by those of ordinary skill in the art, rather than to an absolute or perfect degree. Therefore, the value modified by one or more terms such as "about", "approximately" and "substantially" is not limited to the precise value specified. In at least some cases, approximate language may correspond to the precision of the instrument used to measure the value. Additionally, unless otherwise stated, the terms "first", "second" and the like are used herein only as labels and are not intended to impose order, position or graded requirements on the items to which these terms are related. In addition, for example, a reference to a "second" item does not require or exclude the existence of, for example, a "first" or lower numbered item or a "third" or higher numbered item.

[0084] As used herein, the terms "processor" and "computer," and related terms such as "processing device," "computing device," and "controller" are not limited to those integrated circuits known in the art as computers, but refer generally to microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits, and / or other programmable circuits, and these terms are used interchangeably herein. In the embodiments described herein, memory may include, but is not limited to, computer-readable media such as random access memory (RAM), and computer-readable non-volatile media such as flash memory. Alternatively, floppy disks, compact disk read-only memory (CD-ROMs), magneto-optical disks (MODs), and / or digital versatile disks (DVDs) may be used. Furthermore, in the embodiments described herein, additional input channels may include, but are not limited to, computer peripherals associated with an operator interface, such as a mouse and keyboard. Alternatively, other computer peripherals, such as, but not limited to, scanners, may be used. Furthermore, in the embodiments described herein, additional output channels may include, but are not limited to, an operator interface display.

[0085] As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A vapor compression system circulating a working fluid, the system comprising: a compressor including a compression stage for compressing the working fluid; a first heat exchanger downstream of the compressor, the first heat exchanger receiving and cooling the working fluid; a second heat exchanger downstream of the first heat exchanger and upstream of the compressor, the second heat exchanger receiving and heating the working fluid; and a reservoir positioned between the second heat exchanger and the compression stage, wherein the reservoir defines an internal volume for containing a vapor phase and a liquid phase of the working fluid, wherein the reservoir includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the reservoir and flow toward the compression stage, and wherein the reservoir is operable to atomize the liquid phase of the working fluid into droplets and introduce the droplets into the vapor phase of the working fluid exiting the reservoir. the reservoir includes an ultrasonic transducer positioned in the internal volume to contact the liquid phase of the working fluid and operable to atomize the liquid phase of the working fluid.

2. The vapor compression system of claim 1, wherein, the reservoir includes two or more ultrasonic transducers.

3. The vapor compression system of claim 2, wherein, the inlet is positioned proximate a bottom of the reservoir and the outlet is positioned proximate a top of the reservoir such that the vapor phase of the working fluid flows generally upward within the internal volume toward the outlet and carries relatively small droplets of the liquid phase, and relatively large droplets of the liquid phase separate from the vapor phase and collect within the internal volume.

4. The vapor compression system of claim 1, wherein, the droplets of the liquid phase of the working fluid introduced into the vapor phase transfer heat during compression via heat of vaporization of the droplets.

5. The vapor compression system of claim 1, wherein, 6. The vapor compression system of claim 5, further comprising a controller connected to the reservoir for controlling an amount of the droplets introduced into the vapor phase of the working fluid. the controller is configured to:

7. The vapor compression system of claim 6, further comprising a temperature sensor and a pressure sensor connected to the controller and positioned for monitoring a temperature and a pressure of the working fluid, wherein, determine one or more properties of the working fluid at two or more stages of the vapor compression system based on the monitored temperatures and pressures, and control the amount of the droplets introduced into the vapor phase of the working fluid based on the determined one or more properties. the compressor is a scroll compressor, and wherein the one or more properties include a density of the working fluid.

8. The vapor compression system of claim 7, wherein, the working fluid is a refrigerant blend including a first refrigerant and a second refrigerant, wherein a difference between a boiling point of the first refrigerant and a boiling point of the second refrigerant is greater than or equal to 25°C, and wherein the one or more properties are indicative of concentrations of the first refrigerant and the second refrigerant in the working fluid.

9. The vapor compression system of claim 7, wherein, ​ 10. The vapor compression system of claim 9, wherein, The first and second refrigerants are independently selected from the group consisting of carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1,1,2-tetrafluoroethane (R134A), R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125)), 1,1-difluoroethane (R152a), dimethyl ether (R-E170), propane (R-290), 2,3,3,3-tetrafluoroprop-1-ene (R-1234yf), cis and trans-1,3,3,3-tetrafluoropropene (HFO-1234ye), cis and trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234ze), 3,3,3-trifluoropropene (HFO-1234zf), trifluoro-monochloropropene (HFO-1233), trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd(E)), cis-1-chloro-3,3,3-trifluoropropene (HFO-1233zd(Z)), 2-chloro-3,3,3-trifluoropropene (HFO-1233xf), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(Z)), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(E)), pentafluoropropene (HFO-1225), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,2,3,3,3-pentafluoropropene (HFO-1225yez), hexafluorobutene (HFO-1336), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(Z)), trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)), trans-1,2-difluoroethylene (R-1132(E)), and any isomers or combinations thereof.

11. A method of operating a vapor compression system, the vapor compression system comprising a compressor, a first heat exchanger, a second heat exchanger, and an accumulator, the method comprising: compressing a working fluid at a compression stage of the compressor; cooling the working fluid at the first heat exchanger downstream of the compressor; heating the working fluid at the second heat exchanger downstream of the first heat exchanger; delivering the working fluid into an internal volume of the accumulator downstream of the second heat exchanger and upstream of the compression stage, wherein the working fluid in the internal volume comprises a liquid phase and a vapor phase; delivering the vapor phase of the working fluid from the accumulator toward the compression stage; and atomizing the liquid phase of the working fluid into droplets using the accumulator and introducing the droplets into the vapor phase being delivered toward the compression stage.

12. The method of claim 11, wherein, Atomizing the liquid phase of the working fluid into droplets comprises contacting the liquid phase with an ultrasonic transducer in the internal volume.

13. The method of claim 11, further comprising flowing the vapor phase of the working fluid generally upward within the interior volume from an inlet of the reservoir toward an outlet such that the vapor phase carries relatively smaller droplets of the liquid phase and relatively larger droplets of the liquid phase separate from the vapor phase and collect within the interior volume.

14. The method of claim 11, further comprising transferring heat during compression via evaporation heat of the droplets of the liquid phase introduced into the vapor phase.

15. The method of claim 14, further comprising: monitoring a temperature and a pressure of the working fluid at two or more stages of the vapor compression system; determining one or more properties of the working fluid based on the monitored temperature and pressure, and controlling an amount of the droplets introduced into the vapor phase of the working fluid based on the determined one or more properties.

16. The method of claim 15, wherein, the compressor is a scroll compressor, and wherein the one or more properties include a density of the working fluid.

17. The method of claim 15, wherein, the working fluid is a refrigerant blend including a first refrigerant and a second refrigerant, wherein a difference between a boiling point of the first refrigerant and a boiling point of the second refrigerant is greater than or equal to 25 °C, and wherein the one or more properties are indicative of concentrations of the first refrigerant and the second refrigerant in the working fluid.

18. A vapor compression system that circulates a working fluid including a vapor phase and a liquid phase, the system comprising: a scroll compressor including a compression stage for compressing the working fluid; a first heat exchanger downstream of the compressor that receives and cools the working fluid; a second heat exchanger downstream of the first heat exchanger and upstream of the compressor that receives and heats the working fluid; an atomizer configured to generate droplets of the liquid phase of the working fluid and positioned to introduce the droplets into the vapor phase of the working fluid upstream of the compression stage; and a controller connected to the atomizer and configured to control an amount of the droplets introduced into the vapor phase of the working fluid based on a volumetric ratio of the scroll compressor. the controller is configured to:

19. The vapor compression system of claim 18, further comprising one or more sensors connected to the controller and positioned for monitoring one or more conditions of the working fluid at a first stage upstream of the compression stage and a second stage downstream of the compression stage, and wherein, determine a density of the working fluid at each of the first stage and the second stage based on a monitored condition of the working fluid; compare a ratio of the density to a target volumetric ratio of the scroll compressor; and control the amount of the droplets introduced into the vapor phase of the working fluid based on the comparison. the one or more sensors include temperature sensors and pressure sensors positioned at each of the first stage and the second stage.

20. The vapor compression system of claim 19, wherein, the atomizer is positioned within a housing of the scroll compressor.

21. The vapor compression system of claim 18, wherein, ​

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