VEHICLE HVAC SYSTEM

A vehicle HVAC system includes a compressor, an interior condenser disposed on the downstream side of the compressor, a water-cooled heat exchanger disposed on the downstream side of the interior condenser, and configured to transfer heat between a refrigerant and a coolant circulating in a coolant system, an exterior heat exchanger disposed on the downstream side of the water-cooled heat exchanger, and configured to transfer heat between the refrigerant and ambient air; a refrigerant heat exchanger configured to transfer heat between the refrigerant discharged from the water-cooled heat exchanger and the refrigerant discharged from the interior condenser, and a first control valve located between the water-cooled heat exchanger and the interior condenser, and configured to allow the refrigerant discharged from the interior condenser to be directed to at least one of the water-cooled heat exchanger, the refrigerant heat exchanger, and the exterior heat exchanger.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority to Korean Patent Application No. 10-2023-0088445, filed on Jul. 7, 2023, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to a vehicle heating, ventilation, and air conditioning (HVAC) system, and more particularly, to a vehicle HVAC system designed to improve heating performance and/or dehumidification performance using a refrigerant, thereby increasing electric efficiency of an electric vehicle.

BACKGROUND

With a growing interest in energy efficiency and environmental issues, there is a demand for development of eco-friendly vehicles that can replace internal combustion engine vehicles. Such eco-friendly vehicles are classified into electric vehicles which are driven using fuel cells or electricity as a power source and hybrid vehicles which are driven using an engine and a battery.

Electric vehicles or hybrid vehicles may include a heating, ventilation, and air conditioning (HVAC) system for air conditioning in a passenger compartment. The HVAC system may be configured to heat and cool the air in the passenger compartment for passenger comfort.

In order to ensure driving safety, electric vehicles or hybrid vehicles include a power electronics cooling system designed to maintain power electronic components of a power electronics system at appropriate temperatures, and a battery cooling system designed to maintain a battery at an appropriate temperature. The power electronics cooling system may cool the power electronic components such as an electric motor, an inverter, an on-board charger (OBC), and a low DC-DC converter (LDC), thereby keeping the power electronic components at their respective appropriate temperatures. The battery cooling system may cool the battery, thereby keeping the battery at its appropriate temperature.

A refrigerant circulating in the HVAC system of the electric vehicle may absorb heat from a power electronics coolant circulating in the power electronics cooling system through a water-cooled heat exchanger, and be evaporated.

However, in a condition in which the temperature of ambient air is relatively low (for example, −20° C.-−5° C.), the temperature of the power electronics coolant may be relatively lowered, and accordingly the refrigerant may fail to sufficiently absorb heat from the power electronics coolant. As a result, the evaporation of the refrigerant may be reduced, and a suction pressure of a compressor may be lowered below a threshold pressure. When the suction pressure of the compressor is lower than the threshold pressure, efficiency of the compressor may be reduced, and accordingly RPM of the compressor may be lowered below threshold RPM or the compressor may stop. As a result, the coefficient of performance (COP) of the HVAC system may be degraded. As the heating of the passenger compartment with the use of the refrigerant is not performed, but the passenger compartment is only heated by an electric heater of the HVAC system, electric efficiency of the electric vehicle may be reduced.

In the HVAC system according to the related art, as the heat absorption of the refrigerant is reduced in a condition in which the ambient temperature is relatively low, the amount of evaporation of the refrigerant may be insufficient. Accordingly, the heating of the passenger compartment with the use of the refrigerant may not be smoothly performed due to the RPM reduction or stop of the compressor, and the passenger compartment may be heated by the electric heater so that the electric efficiency of the electric vehicle may be reduced.

While the HVAC system is operating in a heating and dehumidification mode to perform the heating of the passenger compartment and the dehumidification of the passenger compartment at the same time, the HVAC system may automatically control the temperature of the passenger compartment to reach a target temperature. When the temperature of the passenger compartment reaches the target temperature, RPM of a blower may be relatively reduced so that the rate of air blown into the passenger compartment may be relatively reduced. As the rate of air blown into the passenger compartment is reduced, an interior condenser of the HVAC system may fail to sufficiently release heat to the air, and accordingly condensation of the refrigerant in the interior condenser may be insufficient. When the condensation of the refrigerant is insufficient, the dehumidification of the passenger compartment may not be smoothly performed so that fogging may occur on glasses (windows, windshield) of the vehicle, and the suction pressure of the compressor may be increased to the threshold pressure or higher so that the compressor may be forcibly stopped to protect the compressor. When the compressor is forcibly stopped, the electric heater may operate to heat the passenger compartment so that the electric efficiency of the electric vehicle may be reduced.

The above information described in this background section is provided to assist in understanding the background of the inventive concept, and may include any technical concept which is not considered as the prior art that is already known to those skilled in the art.

SUMMARY

An aspect of the present disclosure provides a vehicle heating, ventilation, and air conditioning (HVAC) system designed to improve heating performance and/or dehumidification performance with the use of a refrigerant, thereby increasing electric efficiency of an electric vehicle.

According to an aspect of the present disclosure, a vehicle HVAC system may include a compressor, an interior condenser positioned on a downstream side of the compressor, a water-cooled heat exchanger positioned on a downstream side of the interior condenser, the water-cooled heat exchanger being configured to transfer heat between a refrigerant and a coolant circulating in a coolant system, an exterior heat exchanger positioned on a downstream side of the water-cooled heat exchanger, the exterior heat exchanger being configured to transfer heat between the refrigerant and ambient air, a refrigerant heat exchanger configured to transfer heat between the refrigerant discharged from the water-cooled heat exchanger and the refrigerant discharged from the interior condenser, and a first control valve located between the water-cooled heat exchanger and the interior condenser, the first control valve being configured to allow the refrigerant discharged from the interior condenser to be directed to at least one of the water-cooled heat exchanger, the refrigerant heat exchanger, and the exterior heat exchanger.

The refrigerant heat exchanger may include a first passage through which the refrigerant discharged from the water-cooled heat exchanger passes, and a second passage through which the refrigerant discharged from at least one of the interior condenser and the exterior heat exchanger passes.

The vehicle HVAC system may further include a first bypass line configured to allow at least a portion of the refrigerant discharged from the interior condenser to be directed from an upstream point of the water-cooled heat exchanger to a downstream point of the exterior heat exchanger. The first bypass line may be fluidly connected to the second passage of the refrigerant heat exchanger.

The vehicle HVAC system may further include a second bypass line configured to allow at least a portion of the refrigerant discharged from the interior condenser to be directed from the upstream point of the water-cooled heat exchanger to an upstream point of the exterior heat exchanger. The second bypass line may be fluidly connected to an inlet of the exterior heat exchanger.

The first control valve may include an inlet port communicating with the interior condenser, a first outlet port communicating with the water-cooled heat exchanger, a second outlet port communicating with the first bypass line, and a third outlet port communicating with the second bypass line.

The opening degree of the first outlet port may be adjusted based on a discharge pressure and a discharge temperature of the compressor.

The vehicle HVAC system may further include a third bypass line configured to allow at least a portion of the refrigerant discharged from the water-cooled heat exchanger to be directed from an upstream point of the exterior heat exchanger to an upstream point of the compressor. The third bypass line may be fluidly connected to an inlet of the first passage of the refrigerant heat exchanger.

The vehicle HVAC system may further include a second control valve configured to allow the refrigerant discharged from the water-cooled heat exchanger to be directed to at least one of the exterior heat exchanger and the first passage of the refrigerant heat exchanger.

The second control valve may include: an inlet port communicating with the water-cooled heat exchanger; a first outlet port communicating with the exterior heat exchanger; and a second outlet port communicating with the third bypass line.

The vehicle HVAC system may further include a check valve positioned between the exterior heat exchanger and the second passage of the refrigerant heat exchanger. The check valve may be configured to allow the refrigerant to flow from the exterior heat exchanger to the second passage of the refrigerant heat exchanger, and to prevent the refrigerant from flowing backward from the second passage of the refrigerant heat exchanger to the exterior heat exchanger.

The vehicle HVAC system may further include a cooling-side expansion valve positioned on a downstream side of the second passage of the refrigerant heat exchanger, an evaporator positioned on a downstream side of the cooling-side expansion valve, a distribution line configured to allow at least a portion of the refrigerant discharged from the second passage of the refrigerant heat exchanger to be directed from an upstream point of the cooling-side expansion valve to a downstream point of the evaporator, and a battery chiller fluidly connected to the distribution line, and thermally connected to a battery cooling system.

The vehicle HVAC system may further include a third control valve configured to allow the refrigerant discharged from the second passage of the refrigerant heat exchanger to be directed to at least one of the cooling-side expansion valve and the battery chiller.

The third control valve may include an inlet port communicating with the second passage of the refrigerant heat exchanger, a first outlet port communicating with the cooling-side expansion valve, and a second outlet port communicating with the distribution line.

The opening degree of the first outlet port may be adjusted based on a discharge pressure of the compressor.

The opening degree of the second outlet port may be adjusted based on a suction pressure of the compressor.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals will be used throughout to designate the same or equivalent elements. In addition, a detailed description of well-known techniques associated with the present disclosure will be ruled out in order not to unnecessarily obscure the gist of the present disclosure.

Referring toFIG.1, a vehicle heating, ventilation, and air conditioning (HVAC) system according to an exemplary embodiment of the present disclosure may be configured to heat and cool air in a passenger compartment of the vehicle through a phase change of a circulating refrigerant. The HVAC system may include a refrigerant circulation path30through which the refrigerant is allowed to circulate, and an HVAC case60. The refrigerant circulation path30may be fluidly connected to a compressor11, an interior condenser12, a water-cooled heat exchanger24, an exterior heat exchanger13, a cooling-side expansion valve14, and an evaporator15. The refrigerant circulation path30may allow the flow of the refrigerant to vary depending on various operating modes of a vehicle thermal management system.

The compressor11may compress the refrigerant and allow the refrigerant to circulate. In particular, the compressor11may be configured to compress the refrigerant received from the evaporator15and/or a battery chiller25. The compressor11may include a compressor motor and a compression section operated by the compressor motor. The refrigerant circulation path30may be fluidly connected to the compression section of the compressor11.

The HVAC system may include an accumulator16disposed on the upstream side of the compressor11. The accumulator16may be located between the evaporator15and the compressor11, and the accumulator16may separate a liquid refrigerant from the refrigerant which is received from the evaporator15, thereby preventing the liquid refrigerant from flowing into the compressor11.

The interior condenser12may be configured to condense the refrigerant received from the compressor11, and accordingly the air passing by the interior condenser12may be heated by the interior condenser12. As the air heated by the interior condenser12is directed into the passenger compartment, the passenger compartment may be heated.

The water-cooled heat exchanger24may be disposed on the downstream side of the interior condenser12. The water-cooled heat exchanger24may be thermally connected to a coolant system50. The water-cooled heat exchanger24may be configured to transfer heat between a coolant circulating in the coolant system50and the refrigerant circulating in the refrigerant circulation path30.

According to an exemplary embodiment, the coolant system50may be a power electronics cooling system configured to cool a power electronic component52. The coolant system50may include a coolant circulation path51through which the coolant circulates, the power electronic component52fluidly connected to the coolant circulation path51, a power electronic radiator53fluidly connected to the coolant circulation path51, and a pump54. The power electronic component may be an electric motor, an inverter, and a power conversion component. The power electronic radiator53may be disposed adjacent to a front grille of the vehicle, and the coolant passing through the power electronic radiator53may be cooled by the ambient air forcibly blown by a cooling fan. The power electronic component may have a coolant passage provided inside or outside thereof, and the coolant may pass through the coolant passage. The coolant passage of the power electronic component may be fluidly connected to the coolant circulation path51.

The water-cooled heat exchanger24may include a first passage24afluidly connected to the refrigerant circulation path30, and a second passage24bfluidly connected to the coolant circulation path51. When the temperature of the power electronic component increases, the coolant may absorb heat from the power electronic component so that the temperature of the coolant may relatively increase. The refrigerant passing through the first passage24amay absorb heat from the coolant passing through the second passage24b, and accordingly the refrigerant may be evaporated in the water-cooled heat exchanger24.

The HVAC system according to an exemplary embodiment of the present disclosure may further include a receiver dryer19disposed on the downstream side of the water-cooled heat exchanger24. The receiver dryer19may absorb moisture contained in the refrigerant discharged from the water-cooled heat exchanger24, and store it to smoothly supply the refrigerant. The receiver dryer19may be adjacent to an outlet of the first passage24aof the water-cooled heat exchanger24.

The exterior heat exchanger13may be disposed on the downstream side of the first passage24aof the water-cooled heat exchanger24. The exterior heat exchanger13may have a refrigerant passage provided therein, and the refrigerant may pass through the coolant passage. The exterior heat exchanger13may be disposed adjacent to the front grille of the vehicle, and the exterior heat exchanger13may be exposed to the outside. The exterior heat exchanger13may be configured to transfer heat between the refrigerant and the ambient air. During a cooling operation of the HVAC system, the exterior heat exchanger13may be configured to condense the refrigerant received from the interior condenser12. That is, the exterior heat exchanger13may serve as an exterior condenser that condenses the refrigerant by allowing the refrigerant to release heat to the ambient air during the cooling operation of the HVAC system. During a heating operation of the HVAC system, the exterior heat exchanger13may be configured to evaporate the refrigerant received from the water-cooled heat exchanger24. That is, the exterior heat exchanger13may serve as an exterior evaporator that evaporates the refrigerant by allowing the refrigerant to absorb heat from the ambient air during the heating operation of the HVAC system. In particular, the exterior heat exchanger13may exchange heat with the ambient air forcibly blown by the cooling fan so that a heat transfer rate between the refrigerant and the ambient air may be further increased.

The HVAC system according to an exemplary embodiment of the present disclosure may include a refrigerant heat exchanger26disposed on the upstream side of the compressor11. The refrigerant heat exchanger26may be configured to transfer heat between the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24and/or the evaporator15and the refrigerant discharged from the exterior heat exchanger13and/or the interior condenser12. The refrigerant heat exchanger26may include a first passage26athrough which the refrigerant discharged from the evaporator15and/or the first passage24aof the water-cooled heat exchanger24passes, and a second passage26bthrough which the refrigerant discharged from the exterior heat exchanger13and/or the interior condenser12passes. The first passage26aand the second passage26bmay be fluidly separated from each other.

An inlet of the first passage26amay be located on the downstream side of the first passage24aof the water-cooled heat exchanger24and an outlet of the evaporator15, and accordingly the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24and the outlet of the evaporator15may be directed to the inlet of the first passage26a.

An outlet of the first passage26amay be located on the upstream side of the compressor11, and accordingly the refrigerant discharged from the outlet of the first passage26amay be directed to an inlet of the compressor11.

An inlet of the second passage26bmay be located on the downstream side of an outlet of the exterior heat exchanger13and a first bypass line41, and accordingly the refrigerant discharged from the exterior heat exchanger13and/or the interior condenser12may be directed to the inlet of the second passage26b.

An outlet of the second passage26bmay be located on the upstream side of the cooling-side expansion valve14, and accordingly the refrigerant discharged from the outlet of the second passage26bmay be directed to an inlet of the cooling-side expansion valve14.

The refrigerant heat exchanger26may be configured to transfer heat between the refrigerant passing through the first passage26aand the refrigerant passing through the second passage26b. A temperature of the high-pressure refrigerant discharged from the interior condenser12may be higher than a temperature of the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24. Accordingly, the refrigerant passing through the first passage26amay absorb heat from the refrigerant passing through the second passage26b.

The HVAC system according to an exemplary embodiment of the present disclosure may further include a distribution line45configured to allow at least a portion of the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26to be directed from an upstream point of the cooling-side expansion valve14to a downstream point38aof the evaporator15.

The distribution line45may connect a point between the outlet of the exterior heat exchanger13and the inlet of the cooling-side expansion valve14to the point38abetween an outlet of the evaporator15and the inlet of the compressor11. Specifically, an inlet of the distribution line45may be connected to the refrigerant circulation path30between the second passage26bof the refrigerant heat exchanger26and the inlet of the cooling-side expansion valve14, and an outlet of the distribution line45may be connected to the refrigerant circulation path30between the outlet of the evaporator15and the first passage26aof the refrigerant heat exchanger26. At least a portion of the refrigerant discharged from the exterior heat exchanger13may bypass the cooling-side expansion valve14and the evaporator15through the distribution line45, and be directed to the compressor11. That is, the distribution line45may be configured to allow at least a portion of the refrigerant discharged from the exterior heat exchanger13to bypass the cooling-side expansion valve14and the evaporator15.

The battery chiller25may be fluidly connected to the distribution line45, and the battery chiller25may be configured to transfer heat between the distribution line45and a battery cooling system (not shown). The battery cooling system may be configured to allow a coolant exchanging heat with a battery to circulate. The battery chiller25may be configured to transfer heat between the refrigerant passing through the distribution line45and the coolant circulating in the battery cooling system. That is, the battery chiller25may be thermally connected to the battery cooling system and the distribution line45.

The battery chiller25may include a first passage fluidly connected to the distribution line45, and a second passage fluidly connected to a battery coolant circulation path of the battery cooling system. According to an exemplary embodiment, the battery chiller25may be configured to transfer heat between the refrigerant passing through the first passage of the battery chiller25and the battery coolant passing through the second passage of the battery chiller25. The refrigerant may absorb heat from the battery coolant so that it may be evaporated, and the battery coolant may release heat to the refrigerant so that it may be cooled.

The cooling-side expansion valve14may be disposed on the downstream side of the exterior heat exchanger13and the second passage26bof the refrigerant heat exchanger26, and the cooling-side expansion valve14may be disposed between the second passage26bof the refrigerant heat exchanger26and the evaporator15in the refrigerant circulation path30. The cooling-side expansion valve14may be disposed on the upstream side of the evaporator15, and adjust the flow of the refrigerant and/or the flow rate of the refrigerant into the evaporator15. During the cooling operation of the HVAC system, the cooling-side expansion valve14may be configured to expand the refrigerant received from the exterior heat exchanger13. According to an exemplary embodiment, the cooling-side expansion valve14may be a thermal expansion valve (TXV) which senses the temperature and/or pressure of the refrigerant and adjusts the opening degree of the cooling-side expansion valve14.

The evaporator15may be disposed on the downstream side of the cooling-side expansion valve14, and receive the refrigerant expanded by the cooling-side expansion valve14. The evaporator15may be configured to cool the air using the refrigerant received from the cooling-side expansion valve14. That is, the refrigerant expanded by the cooling-side expansion valve14may absorb heat from the air and be evaporated in the evaporator15. During the cooling operation of the HVAC system, the evaporator15may be configured to cool the air using the refrigerant cooled by the exterior heat exchanger13and expanded by the cooling-side expansion valve14and the air cooled by the refrigerant may be directed into the passenger compartment.

The HVAC system according to an exemplary embodiment of the present disclosure may include a low-pressure refrigerant sensor17disposed on the upstream side of the compressor11and adjacent to the inlet of the compressor11, and a high-pressure refrigerant sensor18disposed on the downstream side of the compressor11and adjacent to an outlet of the compressor11.

The low-pressure refrigerant sensor17may sense the pressure and temperature of the low-pressure refrigerant flowing into the inlet of the compressor11. That is, the low-pressure refrigerant sensor17may sense a suction pressure and suction temperature of the compressor11. In addition, the degree of superheat of the refrigerant may be determined based on the pressure and temperature of the low-pressure refrigerant sensed by the low-pressure refrigerant sensor17. For example, the low-pressure refrigerant sensor17may be located between the inlet of the compressor11and the accumulator16.

The high-pressure refrigerant sensor18may sense the pressure and temperature of the high-pressure refrigerant discharged from the outlet of the compressor11. That is, the high-pressure refrigerant sensor18may sense a discharge pressure and discharge temperature of the compressor11. For example, the high-pressure refrigerant sensor18may be located between the outlet of the compressor11and the interior condenser12.

The HVAC case60may have an inlet and an outlet, and the HVAC case60may be configured to allow the air to be directed toward the passenger compartment of the vehicle. The evaporator15and the interior condenser12may be located inside the HVAC case60. An air mixing door61may be disposed between the evaporator15and the interior condenser12, and an electric heater62such as a positive temperature coefficient (PTC) heater may be disposed on the downstream side of the interior condenser12in an air flow direction.

The HVAC system according to an exemplary embodiment of the present disclosure may further include the first bypass line41configured to allow at least a portion of the refrigerant discharged from the interior condenser12to be directed from an upstream point of the first passage24aof the water-cooled heat exchanger24to a downstream point36aof the exterior heat exchanger13. The first bypass line41may be fluidly connected to the inlet of the second passage26bof the refrigerant heat exchanger26. The first bypass line41may connect a point between an outlet of the interior condenser12and an inlet of the water-cooled heat exchanger24to the point36abetween the outlet of the exterior heat exchanger13and the inlet of the cooling-side expansion valve14. Accordingly, the refrigerant passing through the first bypass line41may bypass the water-cooled heat exchanger24and the exterior heat exchanger13, and be directed to the cooling-side expansion valve14. That is, the first bypass line41may be configured to allow at least a portion of the refrigerant discharged from the interior condenser12to bypass the water-cooled heat exchanger24and the exterior heat exchanger13.

The HVAC system according to an exemplary embodiment of the present disclosure may further include a second bypass line42configured to allow at least a portion of the refrigerant discharged from the interior condenser12to be directed from the upstream point of the first passage24aof the water-cooled heat exchanger24to an upstream point34aof the exterior heat exchanger13. The second bypass line42may be fluidly connected to an inlet of the exterior heat exchanger13. The second bypass line42may connect a point between the outlet of the interior condenser12and the first passage24aof the water-cooled heat exchanger24to a point between the inlet of the exterior heat exchanger13and the first passage24aof the water-cooled heat exchanger24. The refrigerant passing through the second bypass line42may bypass the first passage24aof the water-cooled heat exchanger24, and be directed to the exterior heat exchanger13. That is, the second bypass line42may be configured to allow at least a portion of the refrigerant discharged from the interior condenser12to bypass the water-cooled heat exchanger24.

The HVAC system according to an exemplary embodiment of the present disclosure may include a first control valve21located between the water-cooled heat exchanger24, the interior condenser12, the first bypass line41, and the second bypass line42. The first control valve21may be configured to control the flow of the refrigerant (the direction of the refrigerant, the flow rate of the refrigerant, etc.) between the interior condenser12, the first passage24aof the water-cooled heat exchanger24, the second passage26bof the refrigerant heat exchanger26, and the exterior heat exchanger13. Specifically, the first control valve21may be configured to control the flow of the refrigerant in a manner that allows the refrigerant discharged from the interior condenser12to be directed toward at least one of the first passage24aof the water-cooled heat exchanger24, the second passage26bof the refrigerant heat exchanger26, and the exterior heat exchanger13.

The first control valve21may include an inlet port21acommunicating with the interior condenser12, a first outlet port21bcommunicating with the first passage24aof the water-cooled heat exchanger24, a second outlet port21ccommunicating with the first bypass line41, and a third outlet port21dcommunicating with the second bypass line42.

The inlet port21amay receive the refrigerant discharged from the interior condenser12.

The opening degree of the first outlet port21bmay be adjusted by a controller100so that the refrigerant may be expanded through the first outlet port21band the flow rate of the refrigerant into the water-cooled heat exchanger24may be adjusted. When the opening degree of the first outlet port21bis adjusted, the refrigerant may be expanded at the first outlet port21b, and the expanded refrigerant may be directed to the water-cooled heat exchanger24.

According to an exemplary embodiment, the opening degree of the first outlet port21bmay be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18. As the opening degree of the first outlet port21bis adjusted to a predetermined degree, the refrigerant discharged from the first outlet port21bmay be expanded, and the pressure and temperature of the refrigerant discharged from the first outlet port21bmay be reduced. In particular, when the HVAC system operates in a heating mode, the opening degree of the first outlet port21bmay be adjusted based on the discharge pressure and discharge temperature of the compressor11so that the first outlet port21bmay serve as a heating-side expansion valve that expands the refrigerant directed to the water-cooled heat exchanger24.

According to another exemplary embodiment, the opening degree of the first outlet port21bmay be adjusted based on the degree of superheat of the refrigerant, and the controller100may determine the degree of superheat of the refrigerant based on the pressure and temperature of the refrigerant sensed by the low-pressure refrigerant sensor17. Specifically, when the opening degree of the first outlet port21bis adjusted based on the pressure (the suction pressure of the compressor11) and temperature (the suction temperature of the compressor11) of the low-pressure refrigerant sensed by the low-pressure refrigerant sensor17, the refrigerant discharged from the first outlet port21bmay be expanded, and the pressure and temperature of the refrigerant discharged from the first outlet port21bmay be reduced. In particular, when the HVAC system operates in the heating mode, the opening degree of the first outlet port21bmay be adjusted so that the first outlet port21bmay serve as a heating-side expansion valve that expands the refrigerant directed to the water-cooled heat exchanger24.

In addition, the first outlet port21bmay be fully opened or be fully closed. When the first outlet port21bis fully opened, the refrigerant may be directed to the water-cooled heat exchanger24without expanding.

The opening degree of the second outlet port21cmay be adjusted by the controller100, and an inlet of the first bypass line41may be directly connected to the second outlet port21c. The second outlet port21cmay be opened or closed by the controller100based on whether the HVAC system operates in a heating boost mode or heating enhanced mode. When the HVAC system operates in the heating boost mode or heating enhanced mode, the second outlet port21cmay be opened so that at least a portion of the refrigerant discharged from the interior condenser12may be directed to the first bypass line41.

An inlet of the second bypass line42may be directly connected to the third outlet port21d, and the third outlet port21dmay be opened or closed by the controller100based on whether the HVAC system operates in a dehumidification boost mode or dehumidification enhanced mode. When the HVAC system operates in the dehumidification boost mode or dehumidification enhanced mode, the third outlet port21dmay be opened so that at least a portion of the refrigerant discharged from the interior condenser12may be directed to the second bypass line42.

The HVAC system according to an exemplary embodiment of the present disclosure may further include a third bypass line43configured to allow at least a portion of the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24to be directed from an upstream point of the exterior heat exchanger13to an upstream point of the compressor11.

The third bypass line43may be fluidly connected to the first passage26aof the refrigerant heat exchanger26. The third bypass line43may connect a point between the outlet of the first passage24aof the water-cooled heat exchanger24and the inlet of the exterior heat exchanger13to an upstream point39aof the compressor11. At least a portion of the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may bypass the exterior heat exchanger13through the third bypass line43.

The HVAC system according to an exemplary embodiment of the present disclosure may include a second control valve22located between the water-cooled heat exchanger24, the exterior heat exchanger13, and the third bypass line43. The second control valve22may be configured to control the flow of the refrigerant (the direction of the refrigerant, the flow rate of the refrigerant, etc.) between the first passage24aof the water-cooled heat exchanger24, the exterior heat exchanger13, and the first passage26aof the refrigerant heat exchanger26. Specifically, the second control valve22may be configured to control the flow of the refrigerant in a manner that allows the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24to be directed to at least one of the exterior heat exchanger13and the first passage26aof the refrigerant heat exchanger26.

The second control valve22may include an inlet port22acommunicating with the water-cooled heat exchanger24, a first outlet port22bcommunicating with the exterior heat exchanger13, and a second outlet port22ccommunicating with the third bypass line43. The second outlet port22cmay communicate with the first passage26aof the refrigerant heat exchanger26through the third bypass line43.

The second control valve22may be switched to allow the inlet port22ato communicate with at least one of the first outlet port22band the second outlet port22c. For example, when the second control valve22is switched to allow the inlet port22ato communicate with the second outlet port22c, the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be directed to the first passage26aof the refrigerant heat exchanger26and the compressor11through the third bypass line43. That is, the refrigerant may bypass the exterior heat exchanger13and circulate through the third bypass line43. When the second control valve22is switched to allow the inlet port22ato communicate with the first outlet port22b, the refrigerant discharged from the water-cooled heat exchanger24may be directed to the exterior heat exchanger13without passing through the third bypass line43.

The HVAC system may include a third control valve23located between the second passage26bof the refrigerant heat exchanger26, the cooling-side expansion valve14, and the distribution line45. The third control valve23may be configured to control the flow of the refrigerant (the direction of the refrigerant, the flow rate of the refrigerant, etc.) between the second passage26bof the refrigerant heat exchanger26, the cooling-side expansion valve14, and the battery chiller25. Specifically, the third control valve23may control the flow of the refrigerant in a manner that allows the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26to be directed to at least one of the cooling-side expansion valve14and the battery chiller25.

The third control valve23may include an inlet port23acommunicating with the second passage26bof the refrigerant heat exchanger26, a first outlet port23bcommunicating with the cooling-side expansion valve14, and a second outlet port23ccommunicating with the distribution line45.

The inlet port23amay receive the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26.

The opening degree of the first outlet port23bmay be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18. As the opening degree of the first outlet port23bis adjusted, the flow rate of the refrigerant into the cooling-side expansion valve14may be adjusted. In addition, the first outlet port23bmay be fully opened or be fully closed so that the first outlet port23bmay serve as a shut-off valve located on the upstream side of the cooling-side expansion valve14.

When the first outlet port23bis fully closed, the refrigerant may only be directed to the battery chiller25without being directed to the cooling-side expansion valve14and the evaporator15. That is, when the first outlet port23bis fully closed, the cooling operation of the HVAC system may not be performed, and only the battery chiller25may be cooled or the heating operation of the HVAC system may be performed. When the first outlet port23bis fully opened, the refrigerant may be directed to the cooling-side expansion valve14and the evaporator15. That is, when the first outlet port23bis opened to a predetermined degree, the heating or dehumidification of the passenger compartment may be performed.

The inlet of the distribution line45may be directly connected to the second outlet port23c. The opening degree of the second outlet port23cmay be adjusted according to the state (pressure, temperature, etc.) of the refrigerant, the temperature of the battery, and the like.

The opening degree of the second outlet port23cmay be adjusted based on the pressure (the suction pressure of the compressor11) and temperature (the suction temperature of the compressor11) of the low-pressure refrigerant sensed by the low-pressure refrigerant sensor17. That is, the opening degree of the second outlet port23cmay be adjusted to correspond to the suction pressure and suction temperature of the compressor11so that the refrigerant discharged from the second outlet port23cmay be expanded, and the pressure and temperature of the refrigerant discharged from the second outlet port23cmay be reduced to be substantially equal to the pressure and temperature of the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24. Referring toFIGS.3to5, when the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24and the refrigerant discharged from the second outlet port23cof the third control valve23are joined at a junction39alocated on the upstream side of the first passage26aof the refrigerant heat exchanger26, the opening degree of the second outlet port23cmay be adjusted to correspond to the pressure and temperature of the low-pressure refrigerant sensed by the low-pressure refrigerant sensor17so that the pressure and temperature of the refrigerant discharged from the second outlet port23cmay be similar or equal to the pressure and temperature of the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24.

In addition, when the HVAC system operates in a battery cooling mode for cooling the battery, the opening degree of the second outlet port23cmay be adjusted based on the temperature of the battery so that the second outlet port23cmay serve as a chiller-side expansion valve that expands the refrigerant passing through the battery chiller25. When the opening degree of the second outlet port23cis adjusted, the refrigerant may be expanded at the second outlet port23c, and the expanded refrigerant may be directed to the battery chiller25. As the opening degree of the second outlet port23cis adjusted, the refrigerant discharged from the second outlet port23cmay be expanded, and accordingly the pressure and temperature of the refrigerant discharged from the second outlet port23cmay be reduced. In addition, the second outlet port23cmay be fully opened or be fully closed. When the second outlet port23cis fully opened, the refrigerant may be directed to the battery chiller25without expanding.

Referring toFIG.1, the inlet of the first passage26aof the refrigerant heat exchanger26may be located on the downstream side of the third bypass line43and the downstream side of the evaporator15, and the outlet of the first passage26aof the refrigerant heat exchanger26may be located on the upstream side of the compressor11. The inlet of the second passage26bof the refrigerant heat exchanger26may be located on the downstream side of the exterior heat exchanger13and the downstream side of the first bypass line41, and the outlet of the second passage26bof the refrigerant heat exchanger26may be located on the upstream side of the cooling-side expansion valve14.

Referring toFIG.1, the refrigerant circulation path30may include a first line31extending from the outlet of the compressor11to the interior condenser12, a second line32extending from the interior condenser12to the first control valve21, a third line33extending from the first outlet port21bof the first control valve21to the inlet port22aof the second control valve22, a fourth line34extending from the first outlet port22bof the second control valve22to the inlet of the exterior heat exchanger13, a fifth line35connected to the outlet of the exterior heat exchanger13, a sixth line36extending from the fifth line35to the inlet of the cooling-side expansion valve14, a seventh line37extending from an outlet of the cooling-side expansion valve14to an inlet of the evaporator15, an eighth line38connected to the outlet of the evaporator15, and a ninth line39extending from the eighth line38to the inlet of the compressor11.

The first bypass line41and the fifth line35may be connected to a junction36aof the sixth line36, and the first bypass line41may extend from the second outlet port21cof the first control valve21to the junction36aof the sixth line36located on the upstream side of the refrigerant heat exchanger26. The junction36aof the sixth line36may be located on the upstream side of the second passage26bof the refrigerant heat exchanger26. Accordingly, the first bypass line41may be fluidly connected to the second passage26bof the refrigerant heat exchanger26through the sixth line36.

The second bypass line42may be connected to the fourth line34, and the second bypass line42may extend from the third outlet port21dof the first control valve21to a junction34aof the fourth line34located on the downstream side of the first outlet port22bof the second control valve22. The junction34aof the fourth line34may be located between the first outlet port22bof the second control valve22and the inlet of the exterior heat exchanger13. Accordingly, the second bypass line42may be fluidly connected to the exterior heat exchanger13through the fourth line34.

The third bypass line43and the eighth line38may be connected to a junction39aof the ninth line39, and the third bypass line43may extend from the second outlet port22cof the second control valve22to the junction39aof the ninth line39. The junction39aof the ninth line39may be located on the upstream side of the first passage26aof the refrigerant heat exchanger26. Accordingly, the third bypass line43may be fluidly connected to the first passage26aof the refrigerant heat exchanger26through the ninth line39.

The distribution line45may extend from the second outlet port23cof the third control valve23to a junction38aof the eighth line38. The junction38aof the eighth line38may be located between the junction39aof the ninth line39and the outlet of the evaporator15.

The HVAC system may further include a check valve28disposed between the outlet of the exterior heat exchanger13and the second passage26bof the refrigerant heat exchanger26. The check valve28may be located on the upstream side of the junction36aof the sixth line36. The check valve28may be configured to allow the refrigerant to flow from the exterior heat exchanger13to the second passage26bof the refrigerant heat exchanger26, and prevent the refrigerant from flowing backward from the second passage26bof the refrigerant heat exchanger26to the exterior heat exchanger13.

The controller100may be configured to control respective operations of the compressor11, the first control valve21, the second control valve22, and the third control valve23, and thus the overall operation of the HVAC system may be controlled by the controller100.

FIG.2illustrates the flow of the refrigerant when the HVAC system according to an exemplary embodiment of the present disclosure operates in a heating mode. Referring toFIG.2, as the compressor11operates at predetermined RPM, the compressor11may compress the refrigerant, and the refrigerant discharged from the outlet of the compressor11may be in high temperature and high pressure state. The RPM of the compressor11may be controlled based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18, a duty cycle (or RPM) of the air blower, a vehicle speed, and the like.

The refrigerant compressed by the compressor11may be directed to the interior condenser12, and the interior condenser12may be cooled by the air passing through the HVAC case60so that the refrigerant passing through the interior condenser12may be condensed by the air, and the air may be heated.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18so that the refrigerant discharged from the first outlet port21bmay be expanded. The refrigerant discharged from the first outlet port21bof the first control valve21may be directed to the first passage24aof the water-cooled heat exchanger24, and the refrigerant passing through the first passage24aof the water-cooled heat exchanger24may absorb heat from the coolant passing through the second passage24bof the water-cooled heat exchanger24, and accordingly the refrigerant may be evaporated in the water-cooled heat exchanger24.

The first outlet port22bof the second control valve22may be closed, and the second outlet port22cof the second control valve22may be opened so that the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be directed to the first passage26aof the refrigerant heat exchanger26through the third bypass line43.

When the ambient temperature is relatively low, and the temperature of the coolant is relatively low, the evaporation of the refrigerant in the water-cooled heat exchanger24may be insufficient. In order to improve heating efficiency of the HVAC system, an additional heat source for sufficient evaporation of the refrigerant may be required. Accordingly, the HVAC system may need to operate in a heating boost mode or heating enhanced mode.

FIG.3illustrates the flow of the refrigerant when the HVAC system according to an exemplary embodiment of the present disclosure operates in a heating boost mode or heating enhanced mode. Referring toFIG.3, as the compressor11operates at predetermined RPM, the compressor11may compress the refrigerant, and the refrigerant discharged from the outlet of the compressor11may be in high temperature and high pressure state. The RPM of the compressor11may be controlled based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18, a duty cycle (or RPM) of the air blower, a vehicle speed, and the like.

The refrigerant compressed by the compressor11may be directed to the interior condenser12, and the interior condenser12may be cooled by the air passing through the HVAC case60so that the refrigerant passing through the interior condenser12may be condensed by the air, and the air may be heated. The temperature and pressure of the refrigerant discharged from the interior condenser12may be lower than the temperature and pressure of the refrigerant discharged from the compressor11, but the temperature and pressure of the refrigerant discharged from the interior condenser12may still be high.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the discharge pressure and discharge temperature of the compressor11, and the second outlet port21cof the first control valve21may be opened. Accordingly, the refrigerant discharged from the interior condenser12may be distributed to the water-cooled heat exchanger24and the refrigerant heat exchanger26through the first outlet port21band the second outlet port21cof the first control valve21.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18so that the refrigerant discharged from the first outlet port21bmay be expanded. The pressure and temperature of the refrigerant discharged from the first outlet port21bmay be relatively reduced by the expansion of the refrigerant, compared to the pressure and temperature of the refrigerant flowing into the inlet port21a. The refrigerant discharged from the first outlet port21bmay pass through the first passage24aof the water-cooled heat exchanger24, and the coolant of the coolant system50may pass through the second passage24bof the water-cooled heat exchanger24. The refrigerant passing through the first passage24aof the water-cooled heat exchanger24may absorb heat from the coolant passing through the second passage24bof the water-cooled heat exchanger24so that the refrigerant may be primarily evaporated by the water-cooled heat exchanger24.

The first outlet port22bof the second control valve22may be closed, and the second outlet port22cof the second control valve22may be opened so that the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be directed to the first passage26aof the refrigerant heat exchanger26through the third bypass line43.

The second outlet port21cof the first control valve21may be opened so that a portion of the refrigerant discharged from the interior condenser12may be directed to the second passage26bof the refrigerant heat exchanger26through the second outlet port21cof the first control valve21. Since the refrigerant discharged from the second outlet port21cof the first control valve21is not expanded, the pressure and temperature of the refrigerant discharged from the second outlet port21cmay be maintained the same as the pressure and temperature of the refrigerant flowing into the inlet port21a. Accordingly, the pressure and temperature of the refrigerant discharged from the second outlet port21cmay be higher than the pressure and temperature of the refrigerant discharged from the first outlet port21b. The refrigerant discharged from the second outlet port21cmay be directed to the second passage26bof the refrigerant heat exchanger26through the first bypass line41and the sixth line36.

Since the temperature and pressure of the refrigerant passing through the second passage26bof the refrigerant heat exchanger26are higher than the temperature and pressure of the refrigerant passing through the first passage26aof the refrigerant heat exchanger26, the refrigerant passing through the first passage26amay absorb heat from the refrigerant passing through the second passage26bso that the refrigerant passing through the first passage26amay be secondarily evaporated, and at the same time, the refrigerant passing through the second passage26bmay be secondarily condensed. The refrigerant discharged from the first passage26aof the refrigerant heat exchanger26may be directed to the compressor11after passing through the accumulator16, and the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26may be directed to the first passage26aof the refrigerant heat exchanger26through the third control valve23and the distribution line45.

The first outlet port23bof the third control valve23may be closed, and the second outlet port23cof the third control valve23may be opened to a predetermined degree so that the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26may be directed to the first passage26aof the refrigerant heat exchanger26through the second outlet port23cof the third control valve23and the distribution line45.

The opening degree of the second outlet port23cof the third control valve23may be adjusted to correspond to the pressure (the suction pressure of the compressor11) and temperature (the suction temperature of the compressor11) of the low-pressure refrigerant sensed by the low-pressure refrigerant sensor17so that the refrigerant discharged from the second outlet port23cof the third control valve23may be expanded, and the pressure and temperature of the refrigerant discharged from the second outlet port23cmay be reduced to be substantially equal to the pressure and temperature of the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24. When the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24and the refrigerant discharged from the second outlet port23cof the third control valve23are joined at the junction39alocated on the upstream side of the first passage26aof the refrigerant heat exchanger26, the opening degree of the second outlet port23cmay be adjusted to correspond to the pressure and temperature of the low-pressure refrigerant sensed by the low-pressure refrigerant sensor17so that the pressure and temperature of the refrigerant discharged from the second outlet port23cmay be similar or equal to the pressure and temperature of the low-pressure refrigerant discharged from the first passage24aof the water-cooled heat exchanger24. The refrigerant discharged from the second outlet port23cof the third control valve23may pass through the battery chiller25, be joined to the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24at the junction39a, and then be directed to the compressor11through the first passage26aof the refrigerant heat exchanger26.

When the HVAC system operates in the heating mode in a condition in which the ambient temperature is relatively low (for example, −20° C.-−5° C.), the temperature of the coolant circulating in the coolant circulation path51of the coolant system50may not be relatively high, so the refrigerant passing through the first passage24aof the water-cooled heat exchanger24may fail to sufficiently absorb heat from the second passage24bof the water-cooled heat exchanger24. Accordingly, the refrigerant may not be sufficiently evaporated in the water-cooled heat exchanger24. That is, in the condition in which the ambient temperature is relatively low, the coolant of the coolant system50may fail to provide enough heat for the evaporation of the refrigerant passing through the water-cooled heat exchanger24. To deal with this, the HVAC system according to an exemplary embodiment of the present disclosure may allow the refrigerant heat exchanger to additionally provide heat for the evaporation of the refrigerant in the condition in which the ambient temperature is relatively low. Accordingly, the refrigerant may be evaporated in two steps through the water-cooled heat exchanger24and the refrigerant heat exchanger26, whereby the refrigerant may be sufficiently evaporated. As described above, the refrigerant may be primarily evaporated by the water-cooled heat exchanger24, and be secondarily evaporated by the refrigerant heat exchanger26. Accordingly, as the evaporation of the refrigerant is sufficiently performed, the suction pressure of the compressor may be prevented from being lowered below a predetermined threshold pressure, and the compressor may operate at the predetermined RPM so that efficiency of the compressor may be improved. Since the coefficient of performance (COP) of the HVAC system may be improved with the use of the refrigerant, the operation of the electric heater may be minimized. Thus, electric efficiency of the electric vehicle may be improved.

When the HVAC system operates in the heating and dehumidification mode in a condition in which the ambient temperature is relatively low (for example, −20° C.-−5° C.), the refrigerant may pass through the cooling-side expansion valve14and the evaporator15, and the air passing by the evaporator15may be dehumidified.

FIG.4illustrates the flow of the refrigerant when the HVAC system according to an exemplary embodiment of the present disclosure operates in a heating and dehumidification mode. Referring toFIG.4, as the compressor11operates at predetermined RPM, the compressor11may compress the refrigerant, and the refrigerant discharged from the outlet of the compressor11may be in high temperature and high pressure state. The RPM of the compressor11may be controlled based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18, a duty cycle (or RPM) of the air blower, a vehicle speed, and the like.

The refrigerant compressed by the compressor11may be directed to the interior condenser12, and the interior condenser12may be cooled by the air passing through the HVAC case60so that the refrigerant passing through the interior condenser12may be condensed by the air, and the air may be heated. The temperature and pressure of the refrigerant discharged from the interior condenser12may be lower than the temperature and pressure of the refrigerant discharged from the compressor11, but the temperature and pressure of the refrigerant discharged from the interior condenser12may still be high.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the discharge pressure and discharge temperature of the compressor11, and the second outlet port21cof the first control valve21may be opened. Accordingly, the refrigerant discharged from the interior condenser12may be distributed to the water-cooled heat exchanger24and the refrigerant heat exchanger26through the first outlet port21band the second outlet port21cof the first control valve21.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18so that the refrigerant discharged from the first outlet port21bmay be expanded. The pressure and temperature of the refrigerant discharged from the first outlet port21bmay be relatively reduced by the expansion of the refrigerant, compared to the pressure and temperature of the refrigerant flowing into the inlet port21a. The refrigerant discharged from the first outlet port21bmay pass through the first passage24aof the water-cooled heat exchanger24, and the coolant of the coolant system50may pass through the second passage24bof the water-cooled heat exchanger24. The refrigerant passing through the first passage24aof the water-cooled heat exchanger24may absorb heat from the coolant passing through the second passage24bof the water-cooled heat exchanger24so that the refrigerant may be primarily evaporated by the water-cooled heat exchanger24.

The first outlet port22bof the second control valve22may be closed, and the second outlet port22cof the second control valve22may be opened so that the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be directed to the first passage26aof the refrigerant heat exchanger26through the third bypass line43.

The second outlet port21cof the first control valve21may be opened so that a portion of the refrigerant discharged from the interior condenser12may be directed to the second passage26bof the refrigerant heat exchanger26through the second outlet port21cof the first control valve21. Since the refrigerant discharged from the second outlet port21cof the first control valve21is not expanded, the pressure and temperature of the refrigerant discharged from the second outlet port21cmay be maintained the same as the pressure and temperature of the refrigerant flowing into the inlet port21a. Accordingly, the temperature and pressure of the refrigerant discharged from the second outlet port21cmay be higher than the temperature and pressure of the refrigerant discharged from the first outlet port21b. The refrigerant discharged from the second outlet port21cmay be directed to the second passage26bof the refrigerant heat exchanger26through the first bypass line41and the sixth line36.

Since the temperature and pressure of the refrigerant passing through the second passage26bof the refrigerant heat exchanger26are higher than the temperature and pressure of the refrigerant passing through the first passage26aof the refrigerant heat exchanger26, the refrigerant passing through the first passage26amay absorb heat from the refrigerant passing through the second passage26bso that the refrigerant passing through the first passage26amay be secondarily evaporated, and at the same time, the refrigerant passing through the second passage26bmay be secondarily condensed. That is, the refrigerant primarily evaporated by the water-cooled heat exchanger24may be secondarily evaporated by the refrigerant heat exchanger26so that the evaporation of the refrigerant may be sufficiently performed, and the refrigerant primarily condensed by the interior condenser12may be secondarily condensed by the refrigerant heat exchanger26so that the condensation of the refrigerant may be sufficiently performed.

The refrigerant discharged from the first passage26aof the refrigerant heat exchanger26may be directed to the compressor11after passing through the accumulator16.

The second outlet port23cof the third control valve23may be closed, and the first outlet port23bof the third control valve23may be opened to a predetermined degree so that the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26may be directed to the cooling-side expansion valve14through the first outlet port23bof the third control valve23.

The opening degree of the first outlet port23bof the third control valve23may be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18so that the refrigerant discharged from the second passage26bof the refrigerant heat exchanger26may be primarily expanded at the first outlet port23bof the third control valve23. The refrigerant discharged from the first outlet port23bmay be directed to the cooling-side expansion valve14, and the refrigerant may be secondarily expanded at the cooling-side expansion valve14. The secondarily expanded refrigerant may be evaporated in the evaporator15, and the air passing by an exterior surface of the evaporator15may be cooled and dehumidified. The refrigerant discharged from the evaporator15and the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be joined at the junction39a, and then be directed to the compressor11through the first passage26aof the refrigerant heat exchanger26.

When an interior temperature of the passenger compartment reaches a target temperature, the duty cycle (or RPM) of the air blower may be relatively reduced so that the rate of air blown into the passenger compartment may be relatively reduced. As the rate of the blown air is relatively reduced, the interior condenser of the HVAC system may fail to sufficiently release heat to the air, and thus the condensation of the refrigerant may be relatively reduced. Accordingly, the HVAC system may need to operate in a dehumidification boost mode or dehumidification enhanced mode.

FIG.5illustrates the flow of the refrigerant when the HVAC system according to an exemplary embodiment of the present disclosure operates in a heating and dehumidification boost mode or heating and dehumidification enhanced mode. Referring toFIG.5, as the compressor11operates at predetermined RPM, the compressor11may compress the refrigerant, and the refrigerant discharged from the outlet of the compressor11may be in high temperature and high pressure state. The RPM of the compressor11may be controlled based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18, a duty cycle (or RPM) of the air blower, a vehicle speed, and the like.

The refrigerant compressed by the compressor11may be directed to the interior condenser12, and the interior condenser12may be cooled by the air passing through the HVAC case60so that the refrigerant passing through the interior condenser12may be primarily condensed by the air, and the air may be heated. The temperature and pressure of the refrigerant discharged from the interior condenser12may be lower than the temperature and pressure of the refrigerant discharged from the compressor11, but the temperature and pressure of the refrigerant discharged from the interior condenser12may still be high.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the discharge pressure and discharge temperature of the compressor11, the second outlet port21cof the first control valve21may be closed, and the third outlet port21dof the first control valve21may be opened. Accordingly, the refrigerant discharged from the interior condenser12may be distributed to the water-cooled heat exchanger24and the exterior heat exchanger13through the first outlet port21band the third outlet port21dof the first control valve21.

The opening degree of the first outlet port21bof the first control valve21may be adjusted based on the pressure (the suction pressure of the compressor11) and temperature (the suction temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18so that the refrigerant discharged from the first outlet port21bmay be expanded. The pressure and temperature of the refrigerant discharged from the first outlet port21bmay be relatively reduced by the expansion of the refrigerant, compared to the pressure and temperature of the refrigerant flowing into the inlet port21a. The refrigerant discharged from the first outlet port21bmay pass through the first passage24aof the water-cooled heat exchanger24, and the coolant of the coolant system50may pass through the second passage24bof the water-cooled heat exchanger24. The refrigerant passing through the first passage24aof the water-cooled heat exchanger24may absorb heat from the coolant passing through the second passage24bof the water-cooled heat exchanger24so that the refrigerant may be primarily evaporated by the water-cooled heat exchanger24.

The first outlet port22bof the second control valve22may be closed, and the second outlet port22cof the second control valve22may be opened so that the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be directed to the first passage26aof the refrigerant heat exchanger26through the third bypass line43.

The third outlet port21dof the first control valve21may be opened so that a portion of the refrigerant discharged from the interior condenser12may be directed to the exterior heat exchanger13through the third outlet port21dof the first control valve21and the second bypass line42. The refrigerant passing through the internal refrigerant passage of the exterior heat exchanger13may be secondarily condensed by the ambient air passing by the exterior surface of the evaporator15.

The refrigerant discharged from the exterior heat exchanger13may be directed to the second passage26bof the refrigerant heat exchanger26through the fifth line35and the sixth line36. Since the temperature and pressure of the refrigerant secondarily condensed by the exterior heat exchanger13are higher than the temperature and pressure of the refrigerant evaporated by the water-cooled heat exchanger24, the refrigerant passing through the second passage26bof the refrigerant heat exchanger26may release heat to the refrigerant passing through the first passage26aof the refrigerant heat exchanger26so that the refrigerant secondarily condensed by the exterior heat exchanger13may then be condensed by the refrigerant heat exchanger26. That is, the refrigerant may be primarily condensed by the interior condenser12, be secondarily condensed by the exterior heat exchanger13, and then condensed by the refrigerant heat exchanger26, and thus subcooling of the refrigerant may be sufficiently performed. As the subcooling of the refrigerant is sufficiently performed, the heating and dehumidification of the passenger compartment may be stably performed with the use of the refrigerant. Accordingly, the operation of the electric heater62may be minimized, and thus the electric efficiency of the electric vehicle may be improved.

The second outlet port23cof the third control valve23may be closed, and the opening degree of the first outlet port23bof the third control valve23may be adjusted based on the pressure (the discharge pressure of the compressor11) and temperature (the discharge temperature of the compressor11) of the high-pressure refrigerant sensed by the high-pressure refrigerant sensor18so that the refrigerant discharged from the first outlet port23bmay be primarily expanded. The refrigerant discharged from the first outlet port23bmay be directed to the cooling-side expansion valve14, and the refrigerant may be secondarily expanded at the cooling-side expansion valve14. The secondarily expanded refrigerant may be directed to the evaporator15so that the refrigerant may be evaporated in the evaporator15, and the air passing by the exterior surface of the evaporator15may be cooled and dehumidified. The refrigerant discharged from the evaporator15and the refrigerant discharged from the first passage24aof the water-cooled heat exchanger24may be joined at the junction39a, and then be directed to the compressor11through the first passage26aof the refrigerant heat exchanger26.

As set forth above, according to exemplary embodiments of the present disclosure, when the HVAC system operates in the heating boost mode, the refrigerant may be evaporated twice through the water-cooled heat exchanger and the refrigerant heat exchanger. As the evaporation of the refrigerant is stably performed, the suction pressure of the compressor may be prevented from being lowered below the threshold pressure, and the compressor may operate at the predetermined RPM, and accordingly the efficiency of the compressor may be improved. Since the coefficient of performance (COP) of the HVAC system may be improved using the refrigerant, the operation of the electric heater may be minimized, and thus the electric efficiency of the electric vehicle may be improved.

According to exemplary embodiments of the present disclosure, when the HVAC system operates in the heating and dehumidification boost mode, the refrigerant may be condensed three times through the interior condenser, the exterior heat exchanger13, and the refrigerant heat exchanger. As the condensation of the refrigerant is stably performed, the heating and dehumidification of the passenger compartment may be smoothly performed. Accordingly, the operation of the electric heater may be minimized, and thus the electric efficiency of the electric vehicle may be improved.