System and method for extreme cold starting of a heating system
View Patent ↗A method and system for preventing temperature undershoot in a refrigerant loop during extreme temperatures includes determining a sensed condition at a refrigerant loop and when the sensed condition is below a first threshold starting a flow of coolant in a coolant loop comprising a first portion of a first heat exchanger. The method further includes raising the temperature of the coolant from a heat source to form heated coolant, communicating refrigerant through a second portion of the first heat exchanger, heating the refrigerant in the refrigerant loop at the first heat exchanger from the heated coolant and starting a flow of refrigerant in the refrigerant loop by starting a compressor within the refrigerant loop.
1 . A method comprising:
determining a sensed condition;
when the sensed condition is below a first threshold, starting a flow of coolant in a coolant loop comprising a first portion of a first heat exchanger while not flowing refrigerant in a refrigerant loop;
thereafter, raising a temperature of the coolant from a heat source to form heated coolant; starting a flow of refrigerant in the refrigerant loop by starting a compressor within the refrigerant loop; and heating refrigerant in the refrigerant loop at a second portion of the first heat exchanger from the heated coolant.
2 . The method of claim 1 wherein determining the sensed condition comprises at least one of: determining the temperature within a compressor, determining the temperature within a refrigerant conduit, determining the temperature within a coolant conduit, determining the sensed condition comprises determining an ambient temperature; and determining sensed condition comprises determining a refrigerant pressure.
3 . The method of claim 1 wherein starting the flow in the coolant loop comprises starting the flow in the coolant loop with a coolant pump.
4 . The method of claim 1 wherein raising the temperature of the coolant comprises raising the temperature of the coolant from at least one of a waste heat source, a coolant pump, a propulsion system and a battery housing.
5 . The method of claim 1 further comprising controlling a speed of the compressor based on the sensed condition.
6 . The method of claim 1 further comprising increasing a speed of the compressor based on the sensed condition continuously increasing.
7 . The method of claim 1 further comprising increasing a speed of the compressor based on a continuously increasing the sensed condition until a target speed is reached.
8 . The method of claim 1 further comprising increasing a speed of the compressor when the sensed condition meets a predetermined condition.
9 . The method of claim 8 wherein the sensed condition comprises a refrigerant temperature, and wherein the predetermined condition comprises the refrigerant temperature being below a third threshold between the first threshold and a second threshold, said second threshold less than the first threshold.
10 . The method of claim 1 wherein starting the flow of refrigerant is performed after starting the flow of coolant.
11 . The method of claim 1 further comprising increasing a speed of the compressor when a refrigerant temperature is above a third threshold and the refrigerant temperature is increasing over a time period.
12 . The method of claim 1 wherein starting the flow of refrigerant using the compressor is performed when the sensed condition is above a fourth threshold less than the first threshold.
13 . A system comprising:
a sensed condition sensor determining a sensed condition;
a first heat exchanger;
a coolant loop comprising a first portion of the first heat exchanger;
a refrigerant loop comprising a second portion of the first heat exchanger and a compressor; and
a controller programmed to start a flow of coolant in the coolant loop and prevent flow of refrigerant in the refrigerant loop when the sensed condition is below a first threshold and above a second threshold to raise a temperature of the coolant from a heat source to form heated coolant, thereafter, said controller programmed to start flow of refrigerant and to heat refrigerant in a refrigerant loop at the first heat exchanger from the heated coolant.
14 . The system of claim 13 wherein the controller is programmed to increase a speed of the compressor above the first speed based on a continuously increasing sensed condition.
15 . The system of claim 13 wherein the controller is programmed to increase a speed of the compressor above the first speed based on a continuously increasing sensed condition until a target speed is reached.
16 . The system of claim 13 wherein the controller is programmed to increase a speed of the compressor when the sensed condition meets a predetermined condition.
17 . The system of claim 16 wherein the sensed condition comprises a refrigerant temperature, and wherein the predetermined condition comprises the refrigerant temperature being below a third threshold between the first threshold and the second threshold.
18 . The system of claim 13 wherein the controller is programmed to increase a speed of the compressor when a refrigerant temperature is above a third threshold and the refrigerant temperature is continuously increasing over a time period.
19 . The system of claim 13 wherein the sensed condition sensor comprises at least one of an ambient temperature sensor, a refrigerant pressure sensor, a compressor temperature sensor, and a coolant conduit temperature sensor.
20 . The system of claim 13 further comprising a heat source fluidically coupled to the coolant forming heated coolant; and
a first heat exchanger heating refrigerant in the refrigerant loop from the heated coolant.