Method for controlling vehicle HVAC system

1. A method for controlling a heating, ventilation, and air conditioning (HVAC) system of a vehicle, the method comprising:

determining a target subcooled temperature of a refrigerant based on a temperature and a pressure of the refrigerant discharged from an outlet of a compressor when the compressor operates;

calculating a change in enthalpy of the refrigerant based on the determined target subcooled temperature in a process of condensing and subcooling the refrigerant;

calculating a change in enthalpy of air passing over an exterior surface of a condenser based on the calculated refrigerant enthalpy change; and

calculating a required fan duty of a cooling fan based on the calculated air enthalpy change, wherein the cooling fan is configured to blow the air to the condenser.

2. The method according to claim 1 , wherein the air enthalpy change is calculated based on a temperature difference between the refrigerant and the air, a specific heat of the air, or a flow rate of the refrigerant.

3. The method according to claim 1 , further comprising monitoring a speed of the vehicle and an opening degree of a grille.

4. The method according to claim 3 , wherein the required fan duty of the cooling fan is calculated based on the speed of the vehicle, the opening degree of the grille, and the calculated air enthalpy change.

5. The method according to claim 1 , further comprising:

preliminarily cooling and condensing the refrigerant using a coolant passing through a heat exchanger located on an upstream side of the condenser; and

calculating a change in enthalpy of the coolant based on an RPM of a pump of a cooling system;

wherein the HVAC system is thermally connected to the cooling system through the heat exchanger; and

the required fan duty of the cooling fan is calculated based on the calculated coolant enthalpy change and the calculated air enthalpy change.

6. The method according to claim 5 , wherein the coolant enthalpy change is calculated based on a higher RPM of a first RPM determined by an external controller and a second RPM determined by the controller.

7. The method according to claim 1 , wherein the HVAC system comprises an evaporator, a heater core, an air mixing door, an expansion valve connected to an inlet of the evaporator, the compressor connected to an outlet of the evaporator, and the condenser connected to an outlet of the compressor.

8. The method according to claim 1 , wherein the vehicle comprises an electric vehicle, and wherein the HVAC system comprises an evaporator, the compressor, an interior condenser, a heating-side expansion valve, a water-cooled heat exchanger, an exterior heat exchanger, and a cooling-side expansion valve.

9. The method according to claim 8 , wherein the HVAC system is thermally connected to a battery cooling system through a battery chiller and the water-cooled heat exchanger.

10. The method according to claim 9 , wherein the HVAC system is thermally connected to a powertrain cooling system through the water-cooled heat exchanger.

11. A method for controlling a heating, ventilation, and air conditioning (HVAC) system for a vehicle, the method comprising:

determining whether a compressor operates, a refrigerant passes through an exterior heat exchanger, and a heating-side expansion valve is fully opened;

in response to a determination that the compressor operates, the refrigerant passes through the exterior heat exchanger, and the heating-side expansion valve is fully opened, determining a target subcooled temperature of the refrigerant based on a temperature and a pressure of the refrigerant discharged from an outlet of the compressor;

calculating a change in enthalpy of the refrigerant based on the determined target subcooled temperature;

calculating a change in enthalpy of air passing over an exterior surface of a condenser based on the calculated refrigerant enthalpy change;

calculating a required fan duty of a cooling fan based on the calculated air enthalpy change; and

operating the cooling fan to blow the air to the condenser based on the calculated fan duty.

12. The method according to claim 11 , wherein the air enthalpy change is calculated based on a temperature difference between the refrigerant and the air, a specific heat of the air, or a flow rate of the refrigerant.

13. The method according to claim 11 , further comprising monitoring a speed of the vehicle and an opening degree of a grille.

14. The method according to claim 13 , wherein the required fan duty of the cooling fan is calculated based on the speed of the vehicle, the opening degree of the grille, and the calculated air enthalpy change.

15. The method according to claim 11 , further comprising:

preliminarily cooling and condensing the refrigerant using a coolant passing through the exterior heat exchanger located on an upstream side of the condenser; and

calculating a change in enthalpy of the coolant based on an RPM of a pump of a cooling system;

wherein the HVAC system is thermally connected to the cooling system through the exterior heat exchanger; and

the required fan duty of the cooling fan is calculated based on the calculated coolant enthalpy change and the calculated air enthalpy change.

16. The method according to claim 15 , wherein the coolant enthalpy change is calculated based on a higher RPM of a first RPM determined by an external controller and a second RPM determined by the controller.

17. A heating, ventilation, and air conditioning (HVAC) system for a vehicle, the HVAC system comprising:

a compressor;

a condenser coupled to the compressor;

a cooling fan configured to blow air to the condenser; and

a controller configured to:

determine a target subcooled temperature of a refrigerant based on a temperature and a pressure of the refrigerant discharged from an outlet of the compressor;

calculate a change in enthalpy of the refrigerant based on the determined target subcooled temperature in a process of condensing and subcooling the refrigerant;

calculate a change in enthalpy of air passing over an exterior surface of the condenser based on the calculated refrigerant enthalpy change; and

calculate a required fan duty of the cooling fan based on the calculated air enthalpy change.

18. The HVAC system according to claim 17 , wherein the controller is configured to calculate the air enthalpy change based on a temperature difference between the refrigerant and the air, a specific heat of the air, or a flow rate of the refrigerant.

19. The HVAC system according to claim 17 , wherein the controller is further configured to monitor a speed of the vehicle and an opening degree of a grille.

20. The HVAC system according to claim 19 , wherein the controller is further configured to calculate the required fan duty of the cooling fan based on the speed of the vehicle, the opening degree of the grille, and the calculated air enthalpy change.