KR20070022585A - Compressor with vapor injection system - Google Patents

Abstract

The 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 first and second heat exchanger and scroll compressor. And a flash tank in fluid communication with each. The flash tank includes an inlet fluidly coupled to the first and second heat exchangers and receives liquid refrigerant from the first and second heat exchangers. The flash tank is also fluidly coupled to the first outlet and scroll compressor fluidly coupled to the first and second heat exchangers to supply cooling liquid refrigerant to the second heat exchanger to feed steam refrigerant to the scroll compressor in the heating mode. It includes a second outlet.

Heat pump, heat exchanger, scroll compressor, flash tank, steam refrigerant

Description

COMPRESSOR WITH VAPOR INJECTION SYSTEM}

1 is a schematic diagram of a heat pump system in accordance with the principles of the present invention.

FIG. 2 is a schematic diagram of the heat pump system shown in FIG. 1, illustrating a cooling mode.

3 is a schematic diagram of the heat pump system shown in FIG. 1, illustrating a heating mode.

The present invention relates to steam injection, and more particularly to a heating system having an improved steam injection system.

Heating and / or cooling systems, including air conditioning, chiller, refrigeration and heat pump systems, may include flash tanks disposed between the heat exchanger and the compressor for use in improving system capacity and efficiency. . The flash tank receives liquid refrigerant from the heat exchanger and converts some of the liquid refrigerant into steam for use in the compressor. The flash tank is maintained at a lower pressure than the liquid refrigerant inlet, so that some of the liquid refrigerant vaporizes, and the remaining liquid refrigerant in the flash tank loses heat and is sub-cooled. Steam generated inside the flash tank may be at increased pressure and injected into the compressor to increase the heating and / or cooling capacity of the system.

Vapor refrigerant from the flash tank is distributed to the compressor input at medium pressure. This vapor refrigerant is generally at a higher pressure than the vapor refrigerant leaving the evaporator, but at a lower pressure than the discharge of the refrigerant leaving the compressor, so that the pressurized refrigerant from the flash tank passes through only a portion of the compressor and the compressor is at its normal output pressure. This allows the pressurized refrigerant to be compressed.

Differential cooling refrigerant disposed in the flash tank likewise increases the capacity and efficiency of the heat exchanger. The differential cooling liquid is discharged from the flash tank and sent to one of the heat exchangers depending on the desired mode (ie heating mode or cooling mode). Since this liquid is in a cold 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 pressurized refrigerant flow from the flash tank to the compressor is adjusted to ensure that vapor refrigerant is received by the compressor. Similarly, the flow of differentially cooled liquid refrigerant from the flash tank to the heat exchanger is adjusted to prevent the flow of steam refrigerant from the flash tank to the heat exchanger. The two conditions described above may be controlled by adjusting the flow of the liquid refrigerant into the flash tank. On the other hand, by regulating the flow of the liquid refrigerant flowing into the flash tank, the amount of the steam refrigerant and the differential cooling liquid refrigerant can be controlled, whereby the flow of the vapor refrigerant of the compressor and the differential cooling liquid refrigerant of the heat exchanger can be controlled. .

It is an object of the present invention to improve the capacity and efficiency of the system in both the cooling mode and the heating mode by using a steam injection system in one of the cooling mode and the heating mode and bypassing in the other mode.

The 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 first and second heat exchanger and scroll compressor. And a flash tank in fluid communication with each. The flash tank includes an inlet fluidly coupled to the first and second heat exchangers and receives liquid refrigerant from the first and second heat exchangers. The flash tank is also fluidly coupled to the first outlet and scroll compressor fluidly coupled to the first and second heat exchangers to supply cooling liquid refrigerant to the second heat exchanger to feed steam refrigerant to the scroll compressor in the heating mode. It includes a second outlet.

The field of application of the present invention will become apparent from the detailed description provided hereinafter. It is to be understood that the detailed description and specific examples are given for purposes of illustration only and are not intended to limit the scope of the invention.

The invention will be better understood from the following detailed description and the accompanying drawings.

The following description is merely illustrative in nature and is not intended to limit the invention, its application or use.

Steam injection can be used in air conditioning, chiller, refrigeration and heat pump systems to improve system capacity and efficiency. The steam injection system may include a flash tank for vaporizing the refrigerant supplied to the compressor and cooling the secondary refrigerant supplied to the heat exchanger. Steam injection can be used in heat pump systems that can provide both heating and cooling to commercial and residential buildings to improve one or both of the capacity and efficiency of heating and cooling.

For the same reason, flash tanks can be used in chiller units to provide cooling effects in water, used in refrigeration systems to cool the interior space of display cases or freezers, and used in air conditioning systems to control room and building temperatures. have. Heat pump systems may include cooling cycles and heating cycles, while chiller, refrigeration and air conditioning systems usually include only cooling cycles. However, heat pump chillers that provide heating and cooling cycles are common in some parts of the world. Each system uses a refrigerant that generates the desired cooling or heating efficiency through a cooling cycle.

In the case of air conditioning, refrigeration cycles are used to lower the temperature of the new space to be cooled, typically the room or building. In this case, a fan or blower is used to quickly contact the ambient air with the evaporator to increase heat transfer and cool the surroundings.

In the case of a chiller, the refrigeration cycle cools the water stream. The heat pump chiller uses a refrigeration cycle to heat the water stream when operating in the heating mode. Instead of using a fan or blower, coolant remains on one side of the heat exchanger while circulating water or brine provides a heat source for vaporization. Heat pump chillers usually use ambient air as a heat source for vaporization during the heating mode, but may also use other heat sources, such as heat exchangers or groundwater, which absorb heat from the ground. Thus, the heat exchanger cools or heats the water passing through the heat exchanger as heat is transferred from the water to the refrigerant in the cooling mode and heat is transferred from the refrigerant to the water in the heating mode.

In refrigeration systems such as freezers or frozen display cases, the heat exchanger cools the interior space of the device and releases the heat absorbed by the condenser. Usually a fan or blower is used to contact air in the device's internal space more quickly with the evaporator to increase heat transfer to cool the device's internal space.

In heat pump systems, refrigeration cycles are used for both heating and cooling. The heat pump system may include an indoor unit and an outdoor unit, where the indoor unit performs both cooling and heating of the interior space or room of a commercial or residential building. The heat pump may also consist of a monoblock locator with "outdoor" and "indoor" parts joined in one frame.

As mentioned above, refrigeration cycles can be applied to air conditioning, chillers, heat pump chillers, refrigeration and heat pump systems. Each system has unique features, but steam injection can be used to improve the capacity and efficiency of the system. That is, in each system, steam refrigerant from a flash tank that receives liquid refrigerant from a heat exchanger and converts a portion of the liquid refrigerant into steam can be supplied to a compressor input of medium pressure. This vapor refrigerant is at a higher pressure than the vapor refrigerant leaving the evaporator, but at a lower pressure than the outlet of the refrigerant leaving the compressor. Thus, the compressed refrigerant from the flash tank allows the compressor to compress this compressed refrigerant to its normal output pressure while passing through only part of the compressor. In addition, the differentially cooled refrigerant in the flash tank is useful for increasing the capacity and efficiency of the heat exchanger.

Since the liquid exiting the flash tank is differentially cooled, when supplied to the heat exchanger, more heat can be absorbed from the surroundings, increasing the overall performance of the heating or cooling cycle. Although more specific examples will be provided next with reference to the drawings, those skilled in the art will recognize that the examples described in the present application are made with air conditioning and heaters, but the invention is applicable to other systems and the schedules described in relation to particular types of systems. It should be noted that the feature may be equally applicable to other types of systems.

1 to 3, the operation of the heat pump system 10 will be described in detail. The heat pump system 10 will be described as including a heating mode and a cooling mode with a steam injection system 20 that provides medium pressure steam and differential cooling liquid refrigerant during the heating mode and is bypassed in the cooling mode. Although the steam injection system 20 is described below and shown in the figures as being bypassed in the cooling mode, the steam injection system 20 can optionally be bypassed by the heating mode by simply reversing the arrangement of the system 10. Should know

Referring to FIG. 1, a heat pump system 10 is provided that includes an outdoor unit 12, an indoor unit 14, a scroll compressor 16, an accumulator tank 18, and a steam injection system 20. The indoor and outdoor units 12, 14 are in fluid communication with the scroll compressor 16, the accumulator tank 18, and the vapor injection system 20 so that refrigerant may circulate therebetween. The refrigerant cycles through the system 10 under pressure from the scroll compressor 16 to circulate between the outdoor and indoor units 12, 14 to release and absorb heat. As will be appreciated, whether the outdoor unit or indoor unit 12, 14 will dissipate or receive heat will depend on whether the heat pump system 10 is set to cooling mode or heating mode, Will be discussed. The system may also be a single heating or single cooling system with one single mode of operation.

The outdoor unit 12 includes an outdoor coil or heat exchanger 22 and an outdoor fan 24 driven by a motor 26. The outdoor unit 12 includes a protective housing that houses the outdoor coil 22 and the outdoor fan 24 such that the fan 24 introduces ambient outdoor air to traverse the outdoor coil 22 to improve heat transfer. Let's do it. The outdoor unit 12 also generally houses a scroll compressor 16 and an accumulator tank 18. Although the outdoor unit 12 has been described as including a fan 24 to introduce ambient air to traverse the coil 22, a method of embedding the coil 22 below ground or a water stream around the coil 22. It should be appreciated that any method of transferring heat from coil 22, such as a method of passing, may be considered within the scope of the present invention.

The indoor unit 14 comprises an indoor coil or heat exchanger 28 and an indoor fan 30 driven by a motor 32, which may be a single speed, two speed or variable speed motor. . The indoor fan 30 and the coil 28 are housed in a cabinet so that the fan 30 traverses the internal coil 28 by pressing ambient indoor air at a rate determined by the speed of the variable speed motor 32. As can be appreciated, this air flow across the coil 28 causes heat transfer in the surrounding indoor space and the indoor coil 28. In this regard, the indoor coil 28 in conjunction with the indoor fan 30 selectively raises or lowers the temperature around the room. In addition, although the fan 30 has been disclosed, it should be appreciated that in the chiller, heat is transferred directly from the water stream to the refrigerant, whereby the fan 30 may not be necessary.

The heat pump system 10 includes a four-way reversible valve 34 to provide both cooling and heating by simply inverting the functions of the indoor coil 28 and the outdoor coil 22 as shown. The system may optionally be a single heating or single cooling system with a single mode of operation, in which case the four-way reversible valve 34 may be unnecessary. For systems providing both heating and cooling, when the 4-way valve 34 is set to the cooling mode, the indoor coil 28 functions as an evaporator coil and the outdoor coil 22 functions as a condenser coil. In contrast, when the 4-way valve 34 is switched to the heating mode (replacement position), the functions of the coils 22 and 28 are reversed. That is, the indoor coil 28 functions as a condenser and the outdoor coil 22 functions as an evaporator.

When the indoor coil 28 operates as an evaporator, heat from the surrounding room surroundings is absorbed by the liquid refrigerant moving through the indoor coil 28. This heat transfer between the indoor coil 28 and the liquid refrigerant cools the surrounding indoor air. In contrast, when the indoor coil 28 operates as a condenser, heat from the vapor refrigerant is released by the indoor coil 28 to heat the surrounding indoor air.

A scroll compressor 16 may be housed inside the outdoor unit 12 and pressurizes the heat pump system 10 so that refrigerant is circulated throughout the system 10. The scroll compressor 16 includes a suction port 36, an exhaust port 38, and a steam injection port 40. Discharge port 38 is fluidly coupled to four-way valve 34 by conduit 42 such that compressed refrigerant can be distributed to outdoor and indoor units 12, 14 via four-way valve 34. have. Suction port 36 is fluidly coupled to accumulator tank 18 via conduit 44 such that scroll compressor 16 draws refrigerant from accumulator tank 18 for compression.

Scroll compressor 16 receives refrigerant from intake port 36 from accumulator tank 18, and accumulator tank 18 is fluidly coupled to four-way valve 34 via conduit 46. The accumulator tank 18 also receives refrigerant from the outdoor and indoor units 12, 14 for compression by the scroll compressor 16. The accumulator tank 18 stores the low pressure refrigerant received from the outdoor and indoor units 12, 14 and prevents the compressor 16 from receiving the liquid refrigerant.

Steam injection port 40 is fluidly coupled to steam injection system 20 via conduit 58 and receives compressed refrigerant from steam injection system 20. A check valve 60 may be provided on the conduit 58 between the steam injection port 40 and the steam injection system 20 to allow refrigerant to flow from the steam injection port 40 to the steam injection system 20. Prevent.

The steam injection system 20 produces pressurized steam at a pressure level higher than the pressure supplied by the accumulator tank 18, but at a pressure lower than the pressure produced by the scroll compressor 16. After the pressurized steam reaches the high pressure level, the steam injection system 20 may feed the pressurized refrigerant to the scroll compressor 16 through the steam injection port 40. By feeding the pressurized steam refrigerant to the scroll compressor 16, the capacity and efficiency of the system can be improved. This increase in efficiency may be more pronounced than when the difference between the outdoor temperature and the predetermined room temperature is relatively large (ie during hot or cold weather).

Referring to FIG. 1, the injection vapor system 20 is shown including a flash tank 62, an inlet expansion device 64, an outlet expansion device 66, and a cooling expansion device 68. Each expansion device 64, 66, 68 will be described by a capillary tube and shown in the figures, although the expansion device 64, 66, 68 may optionally be a solenoid valve, a thermal expansion valve or an electronic expansion valve. You should know

The flash tank 62 includes an inlet port 70, a vapor outlet 72, and a differential cooling liquid outlet 74, each fluidly coupled to an internal volume 76. Inlet port 70 is fluidly coupled to outdoor and indoor units 12, 14 via conduits 78, 80. The steam outlet 72 is fluidly coupled to the steam injection port 40 of the scroll compressor 16 via conduits 58, while the differential cooling liquid outlet 74 is connected to the outdoor unit and through the conduits 82, 80. It is fluidly coupled to the indoor units 12, 14.

When the heat pump system 10 is set to the cooling mode (FIG. 2), the steam injection system 20 is bypassed so that no steam is injected into the steam injection port 40 of the compressor 16 and the differential cooling liquid refrigerant is provided. Is not supplied to the indoor heat exchanger 28.

In the cooling mode, the scroll compressor 16 applies a suction force on the accumulator tank 18 to introduce steam refrigerant into the scroll compressor 16. When the vapor is sufficiently pressurized, the high pressure refrigerant is discharged from the scroll compressor 16 through the discharge port 38 and the conduit 42. Four-way valve 34 guides the pressurized refrigerant through conduit 84 to outdoor unit 12. Upon reaching the outdoor coil 22, the refrigerant releases accumulated heat due to the interaction between the outside air, the coil 22, and the pressure exerted by the scroll compressor 16. After the coolant has released a sufficient amount of heat, the coolant phase changes from a gaseous vapor state to a liquid state.

After the refrigerant phase changes from gas to liquid, the refrigerant moves from the outdoor coil 22 through the conduit 80 to the indoor coil 28. A check valve 86 is positioned along the conduit 82 to prevent liquid refrigerant from entering the flash tank 62 at the outlet 74. Since the liquid refrigerant from the outdoor coil 22 is at a higher pressure than the differential cooling liquid refrigerant from the flash tank 62, the differential cooling liquid refrigerant from the flash tank 62 is not mixed with the liquid refrigerant from the outdoor coil 22. Do not.

The capillary tube 68 is disposed approximately between the outdoor unit and the indoor unit 12, 14 along the conduit 80. Capillary tube 68 lowers the pressure of the liquid refrigerant due to the interaction between the moving liquid refrigerant and the inner wall of capillary tube 68. The low pressure of the liquid refrigerant expands the refrigerant before it reaches the indoor unit 14, and the liquid refrigerant begins to transition back to the gaseous state.

Some of the low pressure refrigerant exiting capillary 68 when system 10 is initially started enters inlet 70 of flash tank 62 through conduit 78. The low pressure refrigerant continues to fill the flash tank 62 until the pressure inside the flash tank 62 is equal to the outlet pressure of the capillary 68. Since the pressure of the refrigerant of the steam injection port 40 is higher than the outlet pressure of the capillary tube 68, the low pressure refrigerant does not flow into the steam injection port 40 of the compressor 16. Therefore, during the cooling mode, the internal volume 76 of the flash tank 62 serves as a storage vessel. Since the flow of steam from the flash tank 62 to the steam injection port 40 of the compressor 16 has no continuous flow, no differential cooling liquid refrigerant is generated inside the flash tank 62. As described above, the low pressure refrigerant (ie, the cooling liquid refrigerant) stored during the differential cooling mode does not mix with the refrigerant flowing in the conduit 80 through the outlet 74 of the flash tank 62.

When the indoor unit 14 is reached, the liquid refrigerant enters the indoor coil 28 to complete the transition from the liquid state to the gas state. The liquid refrigerant enters the indoor coil 28 in a low pressure state (due to the interaction of the capillary 68, as described above) and absorbs heat from the environment. As the fan 30 passes air through the coil 28, the refrigerant absorbs heat and completes the phase change to cool the air passing through the indoor coil 28, thus cooling the surroundings. When the coolant reaches the end of the indoor coil 28, the coolant is in a low pressure gas state. At this point, suction from scroll compressor 16 causes the refrigerant to return to accumulator tank 18 via conduit 88 and four-way valve 34.

When the heat pump system 10 is set to the heating mode (FIG. 3), the steam injection system 20 provides medium pressure steam to the steam injection port 40 of the scroll compressor 16 and the cooling liquid refrigerant to the outdoor. To the heat exchanger (22).

In the heating mode, the scroll compressor 16 applies a suction force on the accumulator tank 18 to introduce the vapor refrigerant into the scroll compressor 16. When the vapor is sufficiently pressurized, the high pressure refrigerant is discharged from the scroll compressor 16 through the discharge port 38 and the conduit 42. Four-way valve 34 guides the pressurized refrigerant through conduit 88 to indoor unit 14. Upon reaching the indoor coil 28, the refrigerant releases the accumulated heat due to the interaction between the internal air, the coil 28, and the pressure exerted by the scroll compressor 16, thereby heating the surrounding area. When the coolant releases a sufficient amount of heat, the coolant phase changes from gas, i.e., vapor, to liquid.

As the refrigerant phase changes from gas to liquid, the refrigerant moves from the indoor coil 28 through the conduits 80, 78 to the outdoor coil 22. The liquid refrigerant first moves along conduit 80 until it reaches check valve 90. The check valve 90 limits the subsequent movement of the liquid refrigerant along the conduit 80 from the indoor coil 28 to the outdoor coil 22. As such, the check valve 90 causes the liquid refrigerant to flow into the conduit 78 and meet the capillary tube 64.

Before the refrigerant enters the flash tank 62 at the inlet 70, the capillary tube 68 expands the refrigerant from the indoor coil 28. Expansion of the refrigerant causes the refrigerant to initiate the transition from the liquid state to the gaseous state. As the liquid refrigerant flows through the inlet 70, the internal volume 76 of the flash tank 62 begins to fill. The incoming liquid refrigerant as the volume of the flash tank 62 is filled causes the predetermined internal volume 76 to be pressurized.

When the liquid refrigerant reaches the flash tank 62, the liquid refrigerant releases heat, causing some of the liquid refrigerant to vaporize and some to become a cooling liquid state. At this point, the flash tank 62 has a mixture of both vapor refrigerant and differentially cooled liquid refrigerant. This steam refrigerant is at a higher pressure than the pressure of the steam refrigerant leaving the coils 22, 28 but at a lower pressure than the steam refrigerant leaving the discharge port 38 of the scroll compressor 16.

Steam refrigerant exits the flash tank 62 through the steam outlet 72 and is transferred into the steam injection port 40 of the scroll compressor 16. Pressurized vapor refrigerant causes scroll compressor 16 to feed the outlet refrigerant stream with the desired outlet pressure, thereby improving the overall efficiency of system 10.

The differential cooling liquid refrigerant exits the flash tank 62 through the outlet 74 and reaches the outdoor unit 12 through the conduits 82 and 80. The differential cooling liquid refrigerant leaves the outlet 74 and meets the capillary tube 66. The capillary tube 66 expands the liquid refrigerant before reaching the outdoor coil 22 to improve the performance of the refrigerant extracting heat from the outside. . When the coolant absorbs heat from the outside through the outdoor coil 22, the coolant returns to the gas state once again and returns to the accumulator tank 18 through the conduit 84 and the 4-way valve 34 to resume the cycle. To start.

As mentioned above, the heat pump system 10 provides a steam injection system 20 for use during the heating mode. The steam injection system 20 is bypassed during the cooling mode of the system 10 such that during cooling the differential cooling liquid refrigerant is not received by the indoor unit. However, the heat pump system 10 may optionally include a steam injection system 20 that is used during the differential cooling mode, in which case the steam injection system 20 may be bypassed in the heating mode by simply reversing the arrangement of the system. Can be passed.

The description of the invention is merely exemplary in nature, and therefore, modifications may be made within the scope of the invention without departing from the spirit of the invention. Such changes should be considered as not departing from the spirit and principles of the present invention.

According to the present invention, the steam injection system can be used in one of the cooling mode and the heating mode and bypassed in the other mode, thereby improving the capacity and efficiency of the system in both the cooling mode and the heating mode.

Claims (37)

In heat pump systems: A first heat exchanger operable to pass the refrigerant in the first flow direction and the second flow direction; A second heat exchanger in fluid communication with the first heat exchanger and operable to pass a refrigerant in the first flow direction and the second flow direction; A scroll compressor in fluid communication with each of the first and second heat exchangers and operable to compress the refrigerant in the first flow direction and the second flow direction; And A bypass tube having a suction tube and a first outlet tube in fluid communication with the first and second heat exchangers and a flash tank, for feeding differential cooling liquid refrigerant to the second heat exchanger in the first flow direction. Wherein the bypass tube is disposed between the suction tube and the first outlet tube and creates a pressure difference between the bypass tube and the flash tank such that a cooling liquid refrigerant in the second flow direction is generated. And a fluid circuit operable to prevent flow to the heat exchanger. 2. The heat pump system of claim 1, further comprising an expansion device disposed in the bypass tube and operable to reduce the pressure of the refrigerant in the second flow direction. The heat pump system of claim 1 wherein the expansion device is one of a capillary tube, a thermal expansion valve, and an electrical expansion valve. 10. The heat pump system of claim 1, wherein the scroll compressor comprises a steam injection port in fluid communication with the flash tank and operable to receive steam refrigerant in the first flow direction. 5. The heat pump system of claim 4, further comprising a check valve disposed between said steam injection port and said flash tank to prevent refrigerant flow from said steam injection port to said flash tank. 4. The apparatus of claim 1, wherein the heat pump is disposed at an outlet of the scroll compressor and operable to guide refrigerant in the first flow direction and the second flow direction to selectively change the heat pump between heating and cooling functions. A heat pump system further comprising a way valve. 2. The heat pump system of claim 1, wherein the first flow direction is one of a heating mode and a cooling mode. 8. The heat pump system of claim 7, wherein said second flow direction is the other of said heating mode and said cooling mode. The heat pump system of claim 1, further comprising an expansion device disposed between the first heat exchanger and the flash tank. 10. The heat pump system of claim 9, wherein the expansion device is one of a capillary tube, a solenoid valve, a thermal expansion valve, and an electrical expansion valve. The heat pump system of claim 1, wherein the first heat exchanger is one of a condenser and an evaporator. 12. The heat pump system of claim 11, wherein the second heat exchanger is the other of the condenser and the evaporator. The heat pump system according to claim 1, further comprising an expansion device disposed adjacent said outlet pipe of said flash tank. 14. The heat pump system of claim 13, wherein the expansion device is one of a capillary tube, a solenoid valve, a thermal expansion valve, and an electrical expansion valve. 2. The heat pump system of claim 1, wherein the flash tank comprises a steam injection tube fluidly coupled to the scroll compressor and operable to feed steam refrigerant to the scroll compressor in the first flow direction. A steam injection system in a heat pump system of the type comprising a scroll compressor recirculated through a fluid circuit between a first heat exchanger and a second heat exchanger and coupled to the fluid circuit: A flash tank having a suction tube and a first outlet tube in fluid communication with the first and second heat exchangers and operable to feed the differentially cooled liquid refrigerant to the second heat exchanger in a first flow direction; And A bypass pipe disposed between the suction pipe and the first outlet pipe, wherein a differential pressure is formed between the bypass pipe and the flash tank so that the differential cooling liquid refrigerant flows to the first heat exchanger in a second flow direction. And a bypass tube, the bypass pipe being operable to prevent it from being prevented. 17. The vapor injection system of claim 16, further comprising an expansion device disposed in the bypass tube and operable to reduce the pressure of the refrigerant in the second flow direction. 17. The steam injection system according to claim 16, wherein the expansion device is one of a capillary tube, a thermal expansion valve, and an electric solenoid valve. 17. The vapor injection system of claim 16, wherein the scroll compressor comprises a vapor injection port in fluid communication with the flash tank and operable to receive vapor refrigerant in the first flow direction. 20. The steam injection system of claim 19, further comprising a check valve disposed between the steam injection port and the flash tank to prevent refrigerant flow from the steam injection port to the flash tank. 18. The apparatus of claim 16, wherein the scroll compressor is arranged at an outlet of the scroll compressor and is operable to guide refrigerant in the first flow direction and the second flow direction to selectively change steam injection between heating and cooling functions. Steam injection system further comprises a way valve. 17. The steam injection system according to claim 16, wherein the first flow direction is one of a heating mode and a cooling mode. 23. The steam injection system according to claim 22, wherein said second flow direction is the other of said heating mode and said cooling mode. 17. The vapor injection system of claim 16 further comprising an expansion device disposed between the first heat exchanger and the flash tank. 25. The vapor injection system of claim 24 wherein the expansion device is one of a capillary tube, a solenoid valve, a thermal expansion valve, and an electrical expansion valve. 17. The steam injection system of claim 16 wherein the first heat exchanger is one of a condenser and an evaporator. 27. The vapor injection system of claim 26, wherein the second heat exchanger is the other of the condenser and the evaporator. 17. The steam injection system according to claim 16, further comprising an expansion device disposed adjacent said outlet pipe of said flash tank. 29. The vapor injection system of claim 28 wherein the expansion device is one of a capillary tube, a solenoid valve, a thermal expansion valve, and an electrical expansion valve. 17. The vapor injection system of claim 16, wherein the flash tank includes a vapor injection tube fluidly coupled to the scroll compressor and operable to feed vapor refrigerant to the scroll compressor in the first flow direction. In a heat pump system operable between heating and cooling modes: 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; An inlet fluidly coupled to each of the first and second heat exchangers and the scroll compressor, the inlet fluidly coupled to the first and second heat exchangers, the first fluidly coupled to the first and second heat exchangers. A flash tank comprising a first outlet and a second outlet fluidly coupled to the scroll compressor and operable to feed steam refrigerant to the scroll compressor in a first mode; And An expansion device disposed between the second heat exchanger and the first heat exchanger and operable to reduce the refrigerant to the flash tank to prevent the flash tank from supplying steam refrigerant to the scroll compressor in a second mode Heat pump system comprising a. 32. The heat pump system of claim 31, wherein the expansion device is one of a capillary tube, a solenoid valve, a thermal expansion valve, and an electrical expansion valve. 32. The heat pump system of claim 31, further comprising a check valve disposed adjacent said first outlet of said flash tank to prevent refrigerant from flowing into said first outlet. 32. The heat pump system of claim 31, further comprising an expansion device disposed adjacent said first outlet. 35. The heat pump system of claim 34, wherein the expansion device is one of a capillary tube, a solenoid valve, a thermal expansion valve, and an electrical expansion valve. 32. The heat pump system of claim 31, wherein the first mode is one of a cooling mode and a heating mode. 37. The heat pump system of claim 36, wherein the second mode is the other of the cooling mode and the heating mode.

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