Compressor with vapor injection system

A heat pump system includes a first heat exchanger, a second heat exchanger in fluid communication with the first heat exchanger, a scroll compressor in fluid communication with each of the first and second heat exchangers, and a flash tank in fluid communication with each of the first and second heat exchangers and the scroll compressor. A first capillary tube is disposed between the first heat exchanger and an inlet of the flash tank and a first valve is disposed between the first heat exchanger and the first capillary tube to control refrigerant to the first capillary tube.

FIELD

The present teachings relate to vapor injection and, more particularly, to a heat pump system having an improved vapor injection system.

BACKGROUND

Heating and/or cooling systems including air-conditioning, chiller, refrigeration, and heat pump systems may include a flash tank disposed between a heat exchanger and the compressor for use in improving system capacity and efficiency. The flash tank receives liquid refrigerant from a heat exchanger and converts a portion of the liquid refrigerant into vapor for use by the compressor. Because the flash tank is held at a lower pressure relative to the inlet liquid refrigerant, some of the liquid refrigerant vaporizes, causing the remaining liquid refrigerant in the flash tank to lose heat and become sub-cooled. The resulting vapor within the flash tank is at an increased pressure and may be injected into the compressor to increase the heating and/or cooling capacity of the system.

The vaporized refrigerant from the flash tank is distributed to a medium or intermediate pressure input of the compressor. Because the vaporized refrigerant is at a substantially higher pressure than vaporized refrigerant leaving the evaporator, but at a lower pressure than an exit stream of refrigerant leaving the compressor, the pressurized refrigerant from the flash tank allows the compressor to compress this pressurized refrigerant to its normal output pressure while passing it through only a portion of the compressor.

The sub-cooled refrigerant disposed in the flash tank similarly increases the capacity and efficiency of the heat exchanger. The sub-cooled liquid is discharged from the flash tank and is sent to one of the heat exchangers depending on the desired mode (i.e., heating or cooling). Because the liquid is in a sub-cooled state, more heat can be absorbed from the surroundings by the heat exchanger, thereby improving the overall performance of the heating or cooling cycle.

The flow of pressurized refrigerant from the flash tank to the compressor is regulated to ensure that only vaporized refrigerant is received by the compressor. Similarly, flow of sub-cooled-liquid refrigerant from the flash tank to the heat exchanger is regulated to inhibit flow of vaporized refrigerant from the flash tank to the heat exchanger. Both of the foregoing situations may be controlled by regulating the flow of liquid refrigerant into the flash tank. In other words, by regulating the flow of liquid refrigerant into the flash tank, the amount of vaporized refrigerant and sub-cooled-liquid refrigerant may be controlled, thereby controlling flow of vaporized refrigerant to the compressor and sub-cooled-liquid refrigerant to the heat exchanger.

SUMMARY

A heat pump system includes a first heat exchanger, a second heat exchanger in fluid communication with the first heat exchanger, a scroll compressor in fluid communication with each of the first and second heat exchangers, and a flash tank in fluid communication with each of the first and second heat exchangers and the scroll compressor. A first capillary tube is disposed between the first heat exchanger and an inlet of the flash tank and a first valve is disposed between the first heat exchanger and the first capillary tube to control refrigerant to the first capillary tube.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no way intended to limit the teachings, application, or uses.

Vapor injection may be used in air-conditioning, chiller, refrigeration and heat pump systems to improve system capacity and efficiency. Vapor injection systems may include a flash tank for vaporizing refrigerant supplied to a compressor and sub-cooling refrigerant supplied to a heat exchanger. Vapor injection may be used in heat pump systems, which are capable of providing both heating and cooling to commercial and residential buildings, to improve one or both of heating and cooling capacity and efficiency.

For the same reasons, flash tanks may be used in chiller applications to provide a cooling effect for water, in refrigeration systems to cool an interior space of a display case or refrigerator, and in air-conditioning systems to affect the temperature of a room or building. While heat pump systems may include a cooling cycle and a heating cycle, chiller, refrigeration and air-conditioning systems often only include a cooling cycle. However, heat pump chillers, which provide a heating and cooling cycle, are the norm in some parts of the world. Each system uses a refrigerant to generate the desired cooling or heating effect through a refrigeration cycle.

For air-conditioning applications, the refrigeration cycle is used to lower the temperature of the new space to be cooled, typically a room or building. For this application, a fan or blower is typically used to force the ambient air into more rapid contact with the evaporator to increase heat transfer and cool the surroundings.

For chiller applications, the refrigeration cycle cools or chills a stream of water. Heat pump chillers use the refrigeration cycle to heat a stream of water when operating on HEAT mode. Rather than using a fan or blower, the refrigerant remains on one side of the heat exchanger while circulating water or brine provides the heat source for evaporation. Heat pump chillers often use ambient air as the heat source for evaporation during HEAT mode but may also use other sources such as ground water or a heat exchanger that absorbs heat from the earth. Thus, the heat exchanger cools or heats the water passing therethrough as heat is transferred from the water into the refrigerant on COOL mode and from the refrigerant into the water on HEAT mode.

In a refrigeration system, such as a refrigerator or refrigerated display case, the heat exchanger cools an interior space of the device and a condenser rejects the absorbed heat. A fan or blower is often used to force the air in the interior space of the device into more rapid contact with the evaporator to increase heat transfer and cool the interior space.

In a heat pump system, the refrigeration cycle is used to both heat and cool. A heat pump system may include a second heat exchanger and a first heat exchanger, the second heat exchanger both heats and cools a room or an interior space of a commercial or residential building. The heat pump may also be of a monobloc construction with the “outdoor” and “indoor” parts combined in one frame.

As described previously, the refrigeration cycle is applicable to air conditioning, chiller, heat pump chiller, refrigeration, and heat pump systems. While each system has unique features, vapor injection may be used to improve system capacity and efficiency. That is, in each system, a flash tank receiving liquid refrigerant from a heat exchanger and converting a portion of the liquid refrigerant into vapor, may be supplied to a medium or intermediate pressure input of the compressor. The vaporized refrigerant is at a higher pressure than vaporized refrigerant leaving the evaporator, but at a lower pressure than an exit stream of refrigerant leaving the compressor. The pressurized refrigerant from the flash tank, therefore, allows the compressor to compress this pressurized refrigerant to its normal output pressure while passing it through only a portion of the compressor. Further, the sub-cooled refrigerant in the flash tank is useful to increase the capacity and efficiency of the heat exchanger.

Because the liquid discharged from the flash tank is sub-cooled, when supplied to the heat exchanger, more heat can be absorbed from the surroundings, increasing overall performance of the heating or cooling cycle. More specific examples will be provided next with reference to the drawings, but one of skill in the art should recognize that while the examples described in this application include air conditioning and heating, the teachings are applicable to other systems and certain features described with respect to a particular type of system may be equally applicable to other types of systems.

With reference toFIG. 1, a heat pump system10is provided and includes a first heat exchanger12, a second heat exchanger14, a scroll compressor16, an accumulator tank18, and a vapor injection system20. The first and second heat exchangers12,14are in fluid communication with the scroll compressor16, accumulator tank18, and vapor injection system20such that a refrigerant may circulate therebetween. The refrigerant cycles through the system10under pressure from the scroll compressor16and circulates between the first and second heat exchangers12,14to reject and absorb heat. As can be appreciated, whether the first heat exchanger12or the second heat exchanger14rejects or accepts heat will depend on whether the heat pump system10is set to a COOL mode or a HEAT mode, as will be discussed further below.

The first heat exchanger12includes a first coil or heat exchanger22and first fan24driven by a motor26, which may be a single-speed, two-speed, or variable-speed motor. The first heat exchanger12includes a protective housing that encases the coil22and fan24so that the fan24will draw ambient air across the coil22to improve heat transfer. In addition, the first heat exchanger12usually houses the scroll compressor16and accumulator tank18. While a fan24is disclosed, it should be understood that in a chiller application, heat is transferred from a stream of water directly to the refrigerant and, as such, may obviate the need for the fan24. While first heat exchanger12has been described as including a fan24to draw ambient air across the coil22, it should be understood that any method of transferring heat from the coil22, such as burying the coil22below ground or passing a stream of water around the coil22, is considered within the scope of the present teachings.

The second heat exchanger14includes a second coil or heat exchanger28and a second fan30driven by a motor32, which may be a single-speed, two-speed, or variable-speed motor. The second fan30and coil28are enclosed in a cabinet so that the fan30forces ambient indoor air across the second coil28at a rate determined by the speed of the variable speed motor32. Air flow across the coil28causes heat transfer between the ambient surroundings and the coil28. In this regard, the coil28, in conjunction with the second fan30, selectively raises or lowers the temperature of the surroundings.

Again, while a fan30is disclosed, it should be understood that in a chiller application, heat is transferred from a stream of water directly to the refrigerant and, as such, may obviate the need for the fan30. Furthermore, while the second heat exchanger14has been described as including a fan30to draw ambient air across the coil28, it should be understood that any method of transferring heat from the coil28, such as burying the coil28below ground or passing a stream of water around the coil28, is considered within the scope of the present teachings.

Whether the fans24,30are required for use with the first and second heat exchangers12,14is largely dependent on the application of the first and second heat exchangers12,14. For example, if the first heat exchanger functions in a refrigeration system as a condenser, it may be advantageous to bury the coil22below ground rather than use a fan24. However, in such a system burying the second heat exchanger14, rather than using a fan30, would not be advantageous as the second heat exchanger14functions as an evaporator and would therefore likely use a fan30to circulate air though coil28to cool an interior space of a refrigerator or refrigerated case (neither shown).

The heat pump system10is designated for both cooling and heating by simply reversing the function of the second coil28and the first coil22via a four-way reversing valve34. Specifically, when the four-way valve34is set to the COOL mode, the second coil28functions as an evaporator coil and the first coil22functions as a condenser coil. Conversely, when the four-way valve34is switched to the HEAT mode (the alternate position), the function of the coils22,28is reversed, i.e., the second coil28functions as the condenser and the first coil22functions as the evaporator.

When the second coil28acts as an evaporator, heat from the ambient-indoor surroundings is absorbed by the liquid refrigerant moving through the second coil28. Such heat transfer between the second coil28and the liquid refrigerant cools the surrounding indoor air. Conversely, when the second coil28acts as a condenser, heat from the vaporized refrigerant is rejected by the second coil28, thereby heating the surrounding indoor air.

The scroll compressor16may be housed within the first heat exchanger12and pressurizes the heat pump system10such that refrigerant is circulated throughout the system10. The scroll compressor16includes a suction port36, a discharge port38, and a vapor injection port40. The discharge port38is fluidly connected to the four-way valve34by a conduit42such that pressurized refrigerant may be distributed to the first and second heat exchangers12,14via four-way valve34. The suction port36is fluidly coupled to the accumulator tank18via conduit44such that the scroll compressor16draws refrigerant from the accumulator tank18for compression.

The scroll compressor16receives refrigerant at the suction port36from the accumulator tank18, which is fluidly connected to the four-way valve34via conduit46. In addition, the accumulator tank18receives refrigerant from the first and second heat exchangers12,14for compression by the scroll compressor16. The accumulator tank18stores low-pressure refrigerant received from the first and second coils22,28and protects the compressor16from receiving refrigerant in the liquid state.

The vapor injection port40is fluidly coupled to the vapor injection system20via conduit58and receives pressurized refrigerant from the vapor injection system20. A check valve60may be provided on conduit58generally between the vapor injection port40and the vapor injection system20to prevent refrigerant from flowing from the vapor injection port40to the vapor injection system20.

The vapor injection system20produces pressurized vapor at a higher-pressure level than that supplied by the accumulator tank18, but at a lower pressure than produced by the scroll compressor16. After the pressurized vapor reaches a heightened pressure level, the vapor injection system20may deliver the pressurized refrigerant to the scroll compressor16via vapor injection port40. By delivering pressurized-vapor refrigerant to the scroll compressor16, system capacity and efficiency may be improved. Such an increase in efficiency may be even more pronounced when the difference between the outdoor temperature and the desired indoor temperature is relatively large (i.e., during hot or cold weather).

With reference toFIG. 1, the vapor injection system20is shown to include a flash tank62, a pair of inlet expansion devices64,65, a pair of outlet expansion devices66,67, and a cooling expansion device68. It should be noted that while each of the expansion devices64,65,66,67,68will be described as, and are shown as, capillary tubes, that the expansion devices64,65,66,67,68may alternatively be a thermal expansion valve or an electronic expansion valve. In addition, the vapor injection system20includes a first control valve69adjacent one of the inlet expansion devices64,65and a second control valve71adjacent one of the outlet expansion devices66,67. While the control valves69,71will be described hereinafter as solenoid valves, it should be understood that any control valve that is capable of selectively restricting refrigerant from capillary tubes64,66is considered within the scope of the present teachings.

The flash tank62includes an inlet port70, a vapor outlet72, and a sub-cooled-liquid outlet74, each fluidly coupled to an interior volume76. The inlet port70is fluidly coupled to the first and second heat exchangers12,14via conduits78,79,80. The vapor outlet72is fluidly coupled to the vapor injection port40of the scroll compressor16via conduit58while the sub-cooled-liquid outlet74is fluidly coupled to the outdoor and second heat exchangers12,14via conduits82,83,80.

With particular reference toFIGS. 1-3, operation of the heat pump system10will be described in detail. The heat pump system10will be described as including a COOL mode and a HEAT mode with the vapor injection system20providing intermediate-pressure vapor and sub-cooled liquid refrigerant during the HEAT mode and bypassed in the COOL mode. It should be understood that while the vapor injection system20will be described hereinafter, and shown in the drawings, as being bypassed in the COOL mode, that the vapor injection system20could alternatively be bypassed in the HEAT mode by simply reversing the function of the first and second heat exchangers12,14, and thus the flow of refrigerant through the system10.

When the heat pump system10is set to the COOL mode (FIG. 3), the vapor injection system20is bypassed such that vapor is not injected at the vapor injection port40of the compressor16and sub-cooled liquid refrigerant is not supplied to the second heat exchanger28.

In the COOL mode, the scroll compressor16imparts a suction force on the accumulator tank18to draw vaporized refrigerant into the scroll compressor16. Once the vapor is sufficiently pressurized, the high-pressure refrigerant is discharged from the scroll compressor16via discharge port38and conduit42. The four-way valve34directs the pressurized refrigerant to the first heat exchanger12via conduit84. Upon reaching the first coil22, the refrigerant releases stored heat due to the interaction between the outside air, the coil22, and the pressure imparted by the scroll compressor16. After the refrigerant has released a sufficient amount of heat, the refrigerant changes phase from a gaseous or vaporized phase to a liquid phase.

After the refrigerant has changed phase from gas to liquid, the refrigerant moves from the first coil22to the second coil28via conduit80. A check valve86is positioned along conduit82to prevent the liquid refrigerant from entering the flash tank62at outlet74. Sub-cooled liquid refrigerant from the flash tank62does not mix with the liquid refrigerant from the first coil22as the liquid refrigerant from the first coil22is at a higher pressure than the sub-cooled liquid refrigerant.

Capillary tube68is disposed generally between the first heat exchanger12and the second heat exchanger14along conduit80. The capillary tube68lowers the pressure of the liquid refrigerant due to interaction between the moving liquid refrigerant and the inner walls of the capillary tube68. The lower pressure of the liquid refrigerant expands the refrigerant prior to reaching the second heat exchanger14and begins to transition back to the gaseous phase.

The lower-pressure refrigerant does not enter the flash tank62as the flash tank62is at a higher pressure than the refrigerant exiting the capillary tube68. Therefore, when the system10is set to the COOL mode, refrigerant bypasses the flash tank62and vapor is not injected into the scroll compressor16at vapor injection port40. Because refrigerant does not enter the flash tank62during the COOL mode, sub-cooled liquid refrigerant is not accumulated within the flash tank62. Therefore, the second heat exchanger14does not receive sub-cooled liquid refrigerant during the COOL mode.

Upon reaching the second heat exchanger14, the liquid refrigerant enters the second coil28to complete the transition from the liquid phase to the gaseous phase. The liquid refrigerant enters the second coil28at a low pressure (due to the interaction of the capillary tube68, as previously discussed) and absorbs heat from the surroundings. As the fan30passes air through the second coil28, the refrigerant absorbs heat and completes the phase change, thereby cooling the air passing through the second coil28and, thus, cooling the surroundings. Once the refrigerant reaches the end of the second coil28, the refrigerant is in a low-pressure gaseous state. At this point, the suction from the scroll compressor16causes the refrigerant to return to the accumulator tank18via conduit88and four-way valve34.

When the heat pump system10is set to the HEAT mode (FIG. 2), the vapor injection system20provides vapor at intermediate pressure to the vapor injection port40of the scroll compressor16and sub-cooled liquid refrigerant to the first heat exchanger22.

In the HEAT mode, the scroll compressor16imparts a suction force on the accumulator tank18to draw vaporized refrigerant into the scroll compressor16. Once the vapor is sufficiently pressurized, the high-pressure refrigerant is discharged from the scroll compressor16via discharge port38and conduit42. The four-way valve34directs the pressurized refrigerant to the second heat exchanger14via conduit88. Upon reaching the second coil28, the refrigerant releases stored heat due to the interaction between the inside air, the coil28, and the pressure imparted by the scroll compressor16and, as such, heats the surrounding area. Once the refrigerant has released a sufficient amount of heat, the refrigerant changes phase from the gaseous or vaporized phase to a liquid phase.

Once the refrigerant has changed phase from gas to liquid, the refrigerant moves from the second coil28to the first coil22via conduits80,78, and79. The liquid refrigerant first travels along conduit80until reaching a check valve90. The check valve90restricts further movement of the liquid refrigerant along conduit80from the second coil28to the first coil22. In so doing, the check valve90causes the liquid refrigerant to flow into conduits78,79and encounter solenoid valve69and capillary tube65. The refrigerant further encounters capillary tube64if the solenoid valve69is in an open state.

The solenoid valve69is toggled into the open state to allow refrigerant to encounter capillary tube64when outdoor ambient conditions are high (i.e., when less heat is required indoor). When outdoor ambient conditions are high, more refrigerant enters the flash tank62, as refrigerant is permitted to flow through both capillary tubes64,65. Allowing flow through both capillary tubes64,65decreases resistance to flow and therefore increases the pressure of the refrigerant. Increasing the pressure of the refrigerant decreases the ability of the system10to heat and also prevents low evaporator temperature conditions as well as frost build-up on the first heat exchanger22.

When outdoor ambient conditions are low, solenoid valve69is closed, directing all refrigerant through capillary tube65and bypassing capillary tube64. Bypassing capillary tube64increases resistance to flow and therefore lowers the pressure of the refrigerant. Lowering the refrigerant pressure increases the ability of the system10to heat and is therefore useful during low outside ambient conditions.

It should be noted that in a system using the vapor injection system20during the COOL mode and bypassing the vapor injection system during the HEAT mode, that the solenoid valve69would be open when outdoor ambient conditions are low (i.e., when less cooling effect is required indoor). Conversely, in such a system, solenoid valve69would be closed when outdoor ambient conditions are high (i.e., when a greater cooling effect is required indoor).

The capillary tubes64,65expand the refrigerant from the second coil28prior to the refrigerant entering the flash tank62at inlet70. Expansion of the refrigerant causes the refrigerant to begin to transition from the liquid phase to the gaseous phase. As the liquid refrigerant flows through the inlet70, the interior volume76of the flash tank62begins to fill. The entering liquid refrigerant causes the fixed interior volume76to become pressurized as the volume of the flash tank62is filled.

Once the liquid refrigerant reaches the flash tank62, the liquid releases heat causing some of the liquid refrigerant to vaporize and some of the liquid to enter a sub-cooled-liquid state. At this point, the flash tank62has a mixture of both vaporized refrigerant and sub-cooled-liquid refrigerant. The vaporized refrigerant is at a higher pressure than that of the vaporized refrigerant leaving the first and second coils22,28but at a higher pressure than the vaporized refrigerant leaving the discharge port38of the scroll compressor16.

The vaporized refrigerant exits the flash tank62via the vapor outlet72and is fed into the vapor injection port40of the scroll compressor16. The pressurized vapor-refrigerant allows the scroll compressor16to deliver an outlet refrigerant stream with a desired output pressure, thereby improving the overall efficiency of the system10.

The sub-cooled-liquid refrigerant exits the flash tank62via outlet74and reaches the first heat exchanger12via conduits82,83,80. The sub-cooled-liquid refrigerant leaves outlet74and encounters solenoid valve71and capillary tube67. Capillary tube67expands the liquid refrigerant prior to reaching the first coil22to improve the ability of the refrigerant to extract heat from the outside. The refrigerant further encounters capillary tube66if the solenoid valve71is in an open state.

The solenoid valve71is toggled into the open state to allow refrigerant to encounter capillary tube66when outdoor ambient conditions are high (i.e., when less heat is required indoor). When outdoor ambient conditions are high, more refrigerant exits the flash tank62, as refrigerant is permitted to flow through both capillary tubes66,67. Allowing flow through both capillary tubes66,67decreases resistance to flow and therefore increases the pressure of the refrigerant. Increasing the pressure of the refrigerant decreases the ability of the system10to heat and also prevents low evaporator temperature conditions as well as frost build-up on the first heat exchanger22.

When outdoor ambient conditions are low, solenoid valve71is closed, directing all refrigerant through capillary tube67and bypassing capillary tube66. Bypassing capillary tube66increases resistance to flow and therefore lowers the pressure of the refrigerant. Lowering the refrigerant pressure increases the ability of the system10to heat and is therefore useful during low outside ambient conditions.

It should be noted that in a system using the vapor injection system20during the COOL mode and bypassing the vapor injection system during the HEAT mode, that the solenoid valve71would be open when outdoor ambient conditions are low (i.e., when less cooling effect is required indoor). Conversely, in such a system, solenoid valve71would be closed when outdoor ambient conditions are high (i.e., when a greater cooling effect is required indoor).

The solenoid valves69,71may be used to provide the heat pump system with four configurations to tailor the capacity of the heat pump system10with the ambient conditions. For example, the solenoid valve69could be in a closed state with the solenoid valve71in the open state, solenoid valve69could be in the open state with the solenoid valve71in the closed state, both valves69,71could be in the open state, and both valves69,71could be in the closed state. The above-four valve combinations provide the heat pump system10with the ability to optimize capillary restriction based on outdoor ambient conditions.

As described, the heat pump system10includes a pair of solenoid valves69,71. However, it should be understood that the heat pump system10could alternatively include a single solenoid valve (i.e., either solenoid valve69or71) to minimize the complexity of the system. Such a heat pump system10with a single solenoid valve disposed at either the inlet of the flash tank62(i.e., the position of solenoid valve69) or a solenoid valve disposed at the outlet of the flash tank62(i.e., the position of solenoid valve71) provides the heat pump system with two configurations to tailor the capacity of the heat pump system10with the ambient conditions.

Once the refrigerant absorbs heat from the outside via first coil22, the refrigerant once again returns to the gaseous stage and return to the accumulator tank18via conduit84and four-way valve34to begin the cycle again.

With reference toFIG. 4, a vapor injection system20ais provided and may be used in place of the vapor injection system20shown inFIGS. 1-3. In view of the substantial similarity in structure and function of the components associated with the vapor injection system20with respect to the vapor injection system20a, like reference numerals are used hereinafter and in the drawings to identify like components while like reference numerals containing letter extensions are used to identify those components that have been modified.

The vapor injection system20aincludes capillary tube65disposed proximate to inlet70of the flash tank62and capillary tube67disposed proximate to inlet74of the flash tank62. Capillary tube65expands refrigerant prior to the refrigerant entering the flash tank62to facilitate vaporization while capillary tube67expands the sub-cooled liquid refrigerant to improve the ability of the refrigerant to absorb heat at the first heat exchanger22.

The vapor injection system20aalso includes a solenoid valve69aand an expansion device64adisposed along a conduit78aextending generally between conduit80and an inlet of the first heat exchanger22. When the solenoid valve69ais in an open state, the solenoid valve69aallows refrigerant to encounter capillary tube64asuch that a portion of the refrigerant bypasses the flash tank62. The solenoid valve69ais toggled into the open state when outdoor ambient conditions are high (i.e., when less heat is required indoor).

When outdoor ambient conditions are high, refrigerant is directed through capillary tube65and into the flash tank62and also through capillary tube64a. The refrigerant exiting capillary tube65is expanded by the capillary tube65prior to entering the flash tank62. Once in the flash tank62, the refrigerant is separated into a sub-cooled liquid refrigerant and an intermediate-pressure vapor and is used to increase the capacity of the system, as previously discussed.

The refrigerant exiting capillary tube64ais similarly expanded and is piped directly into an inlet of the first heat exchanger22. The refrigerant bypasses the flash tank62and is directly piped to the first heat exchanger22. Allowing the refrigerant to flow through both capillary tubes64a,65decreases the volume of refrigerant received by the flash tank62and increases the pressure of the refrigerant, thereby reducing the ability of the system to heat. Reducing the ability of the system to heat reduces the likelihood of liquid flood back and frost buildup on the first coil22when ambient conditions are high (i.e., when additional capacity is not required).

When outdoor ambient conditions are low, the solenoid valve69ais closed such that all refrigerant is directed through capillary tube65and into the flash tank62. Directing all refrigerant into the flash tank62increases the volume of refrigerant that reaches the flash tank62and decreases the pressure of the refrigerant, thereby increasing the overall ability of the system to heat as more intermediate-vapor reaches the compressor16and more sub-cooled liquid refrigerant reaches the first coil22.

It should be noted that in a system using the vapor injection system20aduring the COOL mode and bypassing the vapor injection system during the HEAT mode, that the solenoid valve69awould be open when outdoor ambient conditions are low (i.e., when less cooling effect is required indoor) to decrease the ability of the heat pump system to cool. Conversely, in such a system, solenoid valve69awould be closed when outdoor ambient conditions are high (i.e., when more cooling effect is required indoor) to increase the ability of the heat pump system to cool.

With reference toFIG. 5, a vapor injection system20bis provided and may be used in place of the vapor injection system20shown inFIGS. 1-3. In view of the substantial similarity in structure and function of the components associated with the vapor injection system20with respect to the vapor injection system20b, like reference numerals are used hereinafter and in the drawings to identify like components while like reference numerals containing letter extensions are used to identify those components that have been modified.

Vapor injection system20bincludes solenoid valve71and capillary tubes66,67disposed proximate to outlet74of the flash tank62. In addition, capillary tube65disposed proximate to inlet70of the flash tank62. Refrigerant passing through capillary tube65is expanded prior to entering the flash tank62to help facilitate vaporization while refrigerant passing through capillary tubes66,67is expanded to begin the transition from liquid to vapor to aid in the ability of the refrigerant to absorb heat at the first heat exchanger22.

The vapor injection system20bprovides two modes of operation. First, when outdoor ambient conditions are high (i.e., when less heat is required indoor), solenoid valve71may be toggled into the open state to allow refrigerant to encounter capillary tube66. When refrigerant is permitted to encounter capillary tube66, refrigerant flows through conduits82,83and into conduit80prior to reaching the first heat exchanger22. By allowing refrigerant to flow through both capillary tubes66,67, the pressure of the refrigerant is increased and a greater volume of refrigerant reaches the first heat exchanger22. The increased pressure of the refrigerant reduces the ability of the system to heat.

Second, when outdoor ambient conditions are low (i.e., when more heat is required indoor), solenoid valve71may be toggled into the closed state to restrict refrigerant from reaching capillary tube66. By restricting refrigerant from flowing through capillary tube66, the pressure of the refrigerant is reduced and the ability of the system to heat is increased. Therefore, controlling the solenoid valve71between the open and closed states provides the vapor injection system20bwith the ability to adjust to fluctuating outdoor ambient conditions.

Again, it should be noted that in a system using the vapor injection system20bduring the COOL mode and bypassing the vapor injection system20bduring the HEAT mode, that the solenoid valve71would be open when outdoor ambient conditions are low (i.e., when less cooling effect is required indoor) to decrease the ability of the heat pump system to cool. Conversely, in such a system, the solenoid valve71would be closed when outdoor ambient conditions are high (i.e., when a greater cooling effect is required indoor) to increase the ability of the heat pump system to cool.

With reference toFIG. 6, a vapor injection system20cis provided and may be used in place of the vapor injection system20shown inFIGS. 1-3. In view of the substantial similarity in structure and function of the components associated with the vapor injection system20with respect to the vapor injection system20c, like reference numerals are used hereinafter and in the drawings to identify like components while like reference numerals containing letter extensions are used to identify those components that have been modified.

Vapor injection system20cincludes capillary tube65disposed proximate to inlet70of the flash tank62. Refrigerant passing through capillary tube65is expanded prior to entering the flash tank62to help facilitate vaporization. In addition, vapor injection system20calso includes a solenoid valve such as an electronic expansion valve71cdisposed proximate to outlet74of the flash tank62. The expansion valve71cregulates flow out of the flash tank62by controlling an opening between zero and one-hundred percent. While an electronic expansion valve71cis disclosed, it should be understood that any valve capable of regulating flow, such as a thermal expansion valve, could alternatively be used.

The electronic expansion valve71cmay control vapor injection into the compressor16by controlling a volume of sub-cooled liquid refrigerant exiting the flash tank at outlet74. When the electronic expansion valve71cis fully closed (i.e., zero percent open), sub-cooled liquid refrigerant is not permitted to exit the flash tank62and, thus, the flash tank62cannot accept an influx of refrigerant at inlet70. Under such conditions, refrigerant is not expanded within the flash tank62and is therefore not available for use by the compressor16.

When the electronic expansion valve71cis in a fully-open state (i.e., one-hundred percent open), sub-cooled liquid refrigerant is permitted to exit the flash tank62at outlet74and flow to the first heat exchanger22. When sub-cooled liquid refrigerant is permitted to exit the flash tank62, refrigerant is permitted to enter the flash tank62at inlet70and may therefore be expanded into a vapor for use by the compressor16. Therefore, the vapor injection system20cmay be used to control the ability of the system to heat by controlling the state of electronic expansion valve71c.

When ambient outdoor conditions are low, such that additional heating is required, the electronic expansion valve71cis actuated into a position to reduce refrigerant flow (i.e., creates a smaller opening between outlet74and conduit80). Reducing refrigerant flow through outlet74decreases the pressure of the refrigerant and therefore increases the ability of the system to heat. Conversely, when outdoor conditions are high, such that additional heating is not required, the electronic expansion valve71cis opened to allow more refrigerant to flow through outlet74and to increase the pressure of the refrigerant. Increasing the pressure of the refrigerant decreases the ability of the system to heat.

It should be noted that in a system using the vapor injection system20cduring the COOL mode and bypassing the vapor injection system20cduring the HEAT mode, that the electronic expansion valve71cwould be open when outdoor ambient conditions are low (i.e., when less cooling effect is required indoor) to decrease the ability of the heat pump system to cool. Similarly, in such a system, the electronic expansion valve71cwould be partially closed when outdoor ambient conditions are high (i.e., when a greater cooling effect is required indoor) to increase the ability of the heat pump system to cool.

Each of the vapor injection systems20,20a,20b,20cmay be used to regulate refrigerant flowing through the flash tank62to tailor the ability of the heat pump system10to heat based on outdoor ambient conditions. Similarly, each of the vapor injection systems20,20a,20b,20cmay be used to regulate refrigerant flowing through the flash tank62to tailor the ability of the heat pump system10to cool based on outdoor ambient conditions when the flash tank62is bypassed during a HEAT mode.

The description of the teachings is merely exemplary in nature and, thus, variations that do not depart from the gist of the teachings are intended to be within the scope of the teachings. Such variations are not to be regarded as a departure from the spirit and scope of the teachings.