Automotive Heat Pump System
Schematic diagram of traditional automobile air conditioning system
In traditional automobile air conditioning systems, refrigerant can be found in four main states: high-pressure gas, high-pressure liquid, low-pressure liquid, and low-pressure gas. The four key components connecting these four states are compressor, condenser, expansion valve, and evaporator. The compressor compresses the refrigerant in the pipeline. The refrigerant condenses from gas to liquid in the condenser at the front of the engine compartment. This process releases heat. After passing through the expansion valve, the pressure of the liquid refrigerant suddenly decreases. Eventually it vaporizes in the evaporator inside the cabin and absorbs a lot of heat. Thereby achieving the cooling effect in the cabin. The refrigerant in the pipeline mentioned here, also called refrigerant, has the characteristics of easy vaporization and liquefaction to facilitate heat transfer. The earliest widely used refrigerant was Freon. Later, due to Freon's damage to the ozone layer, it was gradually replaced by tetrafluoroethane with the brand name R134A in automotive air conditioning applications. Recently, due to further emphasis on environmental protection, refrigerants have gradually developed towards carbon dioxide refrigerants.
How heat pump thermal management works
The main reason for introducing a heat pump system is that pure electric vehicles or plug-in hybrid vehicles that support pure electric driving can no longer use the engine as a stable heat source for heating. Therefore, before the introduction of the heat pump system, the heating function of the air conditioning system of electric vehicles was mainly completed by electric heaters, also known as resistance PTC (Positive Temperature Coefficient) heaters. And you should know that the heat obtained by direct electric heating will greatly reduce the battery's power and driving range. According to statistics, when driving in winter and turning on the air conditioning heating function based on electric heating, almost half of the electricity is used for heating. Only half of the power is left for driving. Using a heat pump system for heating will significantly increase the mileage.
Heat pump thermal management system cooling mode
In fact, in the heat pump thermal management system, although it is controlled by multiple pumps and valves, there is no component called the heat pump HeatPump. It is called a heat pump because the heat pump system has characteristics similar to that of a water pump in moving water from a low place to a high place. The entire heat pump system can move heat from a place with a low temperature to a place with a high temperature. For example, in summer, the heat pump system does not bring in the low temperature outside the car. On the contrary, it moves the heat inside the car to the outside. Thereby achieving the cooling effect.
Heating mode of heat pump thermal management system
Correspondingly, during heating in winter, the heat pump system sends heat from outside the car to the inside of the car. Then you may want to ask again, can heat be transported in even if it is dozens of degrees below zero outside the car? As mentioned before, there is still heat even at temperatures of tens of degrees below zero. If there is heat, it can be transported.
So how can the heat pump system be applied to the automobile air conditioning system?
First, heat is drawn from the environment into the heat pump system. Secondly, the heat is compressed and heated. Then the heat is used to heat the cold air in the cabin and make it warm. The heated air is sent into the cabin, and the heat after decompression is It is converted into low-temperature heat and discharged outside the vehicle. The heat pump system needs to take into account both heating and cooling conditions. When the stop valves SV1 and SV4 are cut off and SV5 is turned on, the system works in the heating mode. The evaporator in the car in the cooling mode is used as a condenser in the heating mode to provide heat for the cabin together with the hot condenser. In heating mode, the heat pump thermal management system can also transfer the waste heat from the motor, electronic control and charger in the blue coolant pipeline to the red refrigerant air conditioning pipeline through the heat exchanger to provide heat for the cabin. When the stop valves SV1 and SV4 are turned on and SV5 is turned off, the system works in the cooling mode, and the corresponding outdoor condenser in the cooling mode is used as an evaporator in the heating mode.
