In the car, driver comfort is essential. The air-conditioning system is made of an air circuit and a closed refrigerant circuit (air-conditioning loop) and is mandatory to create cabin comfort, but can absorb 5% to 12% of a thermal engine power and up to 50% of the power of an electric engine. Highly aware of environmental issues and forthcoming regulations, Valeo is looking for innovative ways to improve energy efficiency and avoid losses, not just for vehicles with thermal engines (which run on fossil fuels – oil) but also for hybrid and electric vehicles.
The components of an air-conditioning loop are:
Compressor: This compresses the refrigerant in a gaseous state (under high pressure, at a high temperature, in the form of vapor) and sends it to the condenser.
Condenser: located in the front-end of the vehicle, it cools the vapor which returns to its liquid state.
Receiver dryer: this prevents the formation of water (humidification) in the refrigerant.
Expansion valve: this cools the refrigerant before it enters the evaporator by reducing its pressure (bringing it to the same level as the evaporator pressure).
HVAC unit: located bellow the dashboard and attached to the bulkhead (on the engine hood side), it adjusts the temperature and air distribution in the cabin according to the user’s requirements. When it crosses the evaporator, the refrigerant evaporates at a low temperature and low pressure. Then the air passes away the evaporator is cooled, before being blown into the cabin. The radiator heats the air that crosses it, raising the cabin temperature in cold weather.
For electric vehicles, it is possible to mount a heat pump system which operates like a reversible air-conditioning system. This system captures calories from the exterior air, delivering them to the vehicle interior in heating mode and, conversely, evacuates calories from the cabin air to the outside in air-conditioning mode. This system generates significant energy efficiencies and therefore improves battery autonomy.
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The air-conditioning loop is a closed circuit that contains refrigerant only. The refrigerant currently used is R134A. It will soon be replaced by 1234yf.
This refrigerant leaves the compressor in a gaseous state under high pressure, and at a high temperature due to the pressure. It is sent to the condenser, where heat is exchanged between the cold exterior air and the hot fluid. As it cools, the refrigerant condenses and converts from a gaseous to a liquid state. It leaves the condenser as a warm liquid, under a lower pressure. The refrigerant passes through the receiver dryer which captures the water created by condensation. Then it crosses the expansion valve, which reduces the pressure of the refrigerant, thereby cooling it. The decompressed refrigerant then passes through the evaporator, where heat is exchanged between the air flowing into the cabin and the cold refrigerant circulating in the evaporator.When it leaves the evaporator, the refrigerant is warm and does not have enough pressure to travel through the air-conditioning loop, so it is redirected towards the compressor, which repressurizes it again so it can circulate around the loop.
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