Working Principle of Electric Vehicle Air Conditioner
Working principle of electric vehicle air conditioner: heating system
The heated air source of the air conditioning system of fuel vehicles is mainly supplied by engine coolant. The heated air system of electric vehicles is different from that of other vehicles. Common heating solutions for electric vehicle air conditioning systems are as follows:
(1) Heat pump. The figure shows the working principle of an electric vehicle heat pump air conditioning system driven by a drive belt with a DC brushless motor. The cooling/heating mode of the air conditioning system is changed from a four-way reversing valve to a four-way reversing valve. Solid arrows indicate cooling conditions, and dashed arrows indicate heating conditions. In principle, this system is no different from an ordinary heat pump air conditioning system, but it is mainly used in electric vehicles. Specially developed dual-cavity slider compressor, brushless DC motor and inverter control system. When the system changes from defrosting mode to heating mode under heat pump operating conditions, the condensed water on the heat exchanger in the air duct will quickly evaporate and form frost on the window glass, affecting driving safety.
(2) PTC electric heater. PTC electric heater is a heater that uses PTC thermistor as the heat source. PTC thermistors are usually made of semiconductor materials. Their resistance varies greatly with humidity. When the outside temperature decreases, the PTC resistance decreases and the calorific value increases accordingly. According to materials, they can be divided into ceramic PTC thermistors and organic polymer PTC thermistors. Ceramic PTC thermistors are used in air conditioner auxiliary electric heaters. Because its resistance value increases or decreases with changes in ambient temperature, PTC thermistor has the characteristics of energy saving, constant temperature, safety and long service life.
Working principle of electric vehicle air conditioner: refrigeration system
Semiconductor refrigeration is thermoelectric refrigeration, which is a solid-state refrigeration technology. It requires no refrigerant. The thermopile acts as a compression refrigeration compressor. The cold end and its heat exchanger are equivalent to the compression refrigeration evaporator, and the hot end and its heat exchanger are equivalent to the condenser. After energization, free electrons and holes move from the cold end of the thermopile to the hot end under the action of an external electric field, which is equivalent to the compression process of the refrigerant in the compressor. At the cold end of the electrothermal reactor, the heat exchanger absorbs heat and generates electron-hole pairs at the same time, which is equivalent to the heat absorption and evaporation of the refrigerant in the evaporator. At the hot end of the electrothermal reactor, electron-hole pairs recombine, and heat is dissipated through the heat exchanger, which is equivalent to the heating and condensation of the refrigerant in the condenser.
Thermoelectric air conditioners have the following characteristics: thermoelectric elements require DC power; changing the direction of the current can produce the reverse effect of cooling and heating; thermoelectric refrigeration pieces have small thermal inertia and short refrigeration time. When the hot end has good heat dissipation and the cold end has no load, the refrigeration chip can reach the maximum temperature difference within 1 minute of power on. By adjusting the working current of the module, the refrigeration speed and temperature can be adjusted, the temperature control accuracy can reach 0.001 degrees Celsius, and the energy can be continuously adjusted. Under correct design and usage conditions, the refrigeration efficiency can reach more than 90%. It has no rotating parts and therefore no vibration, friction, noise and impact resistance.
Working principle of electric vehicle air conditioning: principle of heat pump air conditioning system
Air conditioning auxiliary electric heaters can be divided into bonded ceramic PTC heaters and metal PTC tube heaters. Bonded ceramic PTC heater is a heater made of high temperature resistant resin bonded with many ceramic PTC chips and aluminum corrugated heat sink. It has good heat dissipation performance and stable electrical performance. Bonded ceramic PTC heaters can be divided into two types: charged heater surface and non-charged heater surface.
The metal PTC tube heater uses imported nickel-iron alloy wire as the heating material, and the heat pipe is equipped with an aluminum radiator. The heat dissipation effect is very good. The heater is equipped with a temperature controller and thermal fuse, making the product safer and more reliable. This heater has good PTC material properties. Some air conditioners use this heater as auxiliary heating.
(3) Waste heat assists PTC. The heat generated by high-power equipment (power conversion, drive motors, motor controllers, etc.) is used for heat exchange with the vehicle's internal environment. When the heat is insufficient, the auxiliary PTC heater starts.
