Vehicle vapor-injection heat pump system with controllable evaporator valve
A vehicle includes a vapor-injection heat pump having a refrigerant loop with an evaporator configured to cool cabin air, the evaporator coupled to an electronically controllable pressure regulating valve having a fully-open position with near-zero pressure drop, and a cabin conditioning coolant loop having a heater core configured to selectively heat the cabin air. A controller is configured to control the valve to maintain temperature and pressure of the refrigerant loop above a freezing threshold to inhibit or prevent evaporator icing. The valve may be controlled to throttle flow during a parallel dehumidification mode and to fully open to minimize pressure drop during other operational modes, such as a cooling mode, heating mode, de-icing mode, and series dehumidification mode.
1. A vehicle comprising:
a refrigerant loop including an electrically operable compressor coupled to a cabin conditioning heat exchanger, an electronically controlled expansion valve, an external air heat exchanger and an evaporator configured to cool cabin air, wherein the evaporator is coupled to an electronically controlled evaporator pressure regulator positioned between the evaporator and the compressor;
a cabin conditioning loop including the cabin conditioning heat exchanger, an electrically operated coolant heater, and a heater core configured to heat the cabin air;
a battery conditioning loop selectively fluidly coupled to the cabin conditioning loop via a fluid control valve, and coupled to the refrigerant loop by a battery heat exchanger; and
a controller configured to operate the electrically operated coolant heater to heat the cabin air simultaneously with the compressor to cool the cabin air to provide a parallel dehumidification mode, and to control the electronically controlled evaporator pressure regulator to throttle refrigerant flow only during the parallel dehumidification mode, and to control the electronically controlled evaporator pressure regulator to a fully open position when not operating in the parallel dehumidification mode.
2. The vehicle of claim 1 further comprising a temperature sensor configured to provide a signal to the controller indicative of temperature of cooling fins of the evaporator, wherein the controller is further configured to control the electronically controlled evaporator pressure regulator in response to the temperature of the cooling fins.
3. The vehicle of claim 2 further comprising a pressure sensor configured to provide a signal to the controller indicative of refrigerant pressure in the evaporator, wherein the controller is further configured to control the electronically controlled evaporator pressure regulator in response to the refrigerant pressure in the evaporator.
4. The vehicle of claim 1 wherein the controller is further configured to operate the fluid control valve to provide heating or cooling of coolant in the battery conditioning loop.
5. The vehicle of claim 1 further comprising a traction battery coupled to the electrically operated coolant heater.
6. The vehicle of claim 5 wherein the traction battery powers the compressor.