Heat pump secondary coolant loop heat exchanger defrost system for a motor vehicle

A defrost system for a low temperature radiator of a cooling and heating system for a motor vehicle, the cooling and heating system comprising:

• a refrigerant-based heat pump having a first side heat exchanger and a second side heat exchanger, wherein the heat pump is adapted to operate in a cooling mode and a heating mode;
• a controller for controlling operation and determining the operation of the cooling and heating system;
• a first secondary coolant loop comprising the low temperature radiator, the low temperature radiator being in thermal communication with the first side heat exchanger of the heat pump when the heat pump is in the cooling mode and the low temperature radiator being in thermal communication with the second side heat exchanger of the heat pump when the heat pump is in the heating mode;
• and
• a second secondary coolant loop comprising a passenger cabin heat exchanger, the passenger cabin heat exchanger being in thermal communication with the second side heat exchanger of the heat pump when the heat pump is in the cooling mode and the passenger cabin heat exchanger being in thermal communication with the first side heat exchanger of the heat pump when the heat pump is in the heating mode;
• wherein the defrost system comprises a bypass coolant loop in selective fluid communication with the first secondary coolant loop and upstream of the low temperature radiator, a coolant storage and heating tank in series fluid communication within the bypass coolant loop, a coolant heater comprising a coolant electric resistance heating element disposed within the coolant storage and heating tank, and a solenoid valve in series fluid communication within the bypass coolant loop and with the coolant storage and heating tank;
• wherein, in the heating mode, the controller opens or confirms open the solenoid valve in the bypass coolant loop and activates the coolant heater upon detecting that the low temperature radiator is covered in frost and/or ice and upon detecting an ambient temperature below a predetermined temperature, and wherein the controller de-activates the coolant heater and closes the solenoid valve in the bypass coolant loop upon detecting that the low temperature radiator is not covered in frost and/or ice.

A heat pump system for a motor vehicle comprising:

• a refrigerant-based heat pump having a first side heat exchanger and a second side heat exchanger, wherein the heat pump is adapted to operate in a cooling mode and a heating mode;
• a controller for controlling operation of the heat pump system;
• a first secondary coolant loop comprising a low temperature radiator, the low temperature radiator being in thermal communication with the first side heat exchanger of the heat pump when the heat pump is in the cooling mode and the low temperature radiator being in thermal communication with the second side heat exchanger of the heat pump when the heat pump is in the heating mode;
• a second secondary coolant loop comprising a passenger cabin heat exchanger, the passenger cabin heat exchanger being in thermal communication with the second side heat exchanger of the heat pump when the heat pump is in the cooling mode and the passenger cabin heat exchanger being in thermal communication with the first side heat exchanger of the heat pump when the heat pump is in the heating mode;
• and
• a defrost system comprising a bypass coolant loop in selective fluid communication with the first secondary coolant loop and upstream of the low temperature radiator, a coolant heater in series fluid communication within the bypass coolant loop, and a solenoid valve in series fluid communication within the bypass coolant loop and the coolant heater;
• wherein, in the heating mode, the controller opens the solenoid valve in the bypass coolant loop and activates the coolant heater upon detecting that the low temperature radiator is covered in frost and/or ice and upon detecting an ambient temperature below a predetermined temperature, and wherein the controller de-activates the coolant heater and closes the solenoid valve in the bypass coolant loop upon detecting that the low temperature radiator is not covered in frost and/or ice.