The air conditioner can only operate when the car engine is running. The operating principle can be summarized as follows. Compressor 1, Figure 8-67, constantly compresses and circulates the refrigerant. When compressed, the gaseous refrigerant passes into a liquid state, condensing in the heat exchanger-condenser with the release of heat. Then, when it passes back into a gaseous state (evaporation), heat is absorbed in the heat exchanger-evaporator.
Figure 8-67. Air conditioner operation diagram:
1 - compressor;
2 - capacitor;
3 - receiver;
4 - thermostatic expansion valve (TEV);
5 - evaporator;
"bands" - compressed gas with high pressure and temperature;
"dots" - liquid phase of the refrigerant;
"white" - fog-like phase and superheated steam.
The evaporator 5 located in the car's interior constantly reduces the air temperature. The refrigerant transfers the "latent" heat to the condenser 2 located outside the interior and is released from it. This cycle is continuously repeated and, accordingly, heat is constantly removed from the interior to the atmosphere. Controls and actuators allow maintaining the desired microclimate.
Attention: the air conditioning system of the CHEVROLET NIVA vehicle uses R 134a refrigerant.
Compressor 1, Figure 8-68, is the main and most complex unit of the system. The compressor compresses the low-temperature, low-pressure gaseous refrigerant, converting it into high-temperature, high-pressure gas. The compressor is mounted on the engine bracket on the right side.
The compressor is driven by a poly-V drive belt from the car engine through an electromagnetic clutch. When voltage is applied to its winding, the driven disk and pulley rotate synchronously, setting the compressor shaft in motion.
Lubrication of the compressor is performed by a special compressor oil, circulating throughout the system together with the refrigerant. The air conditioning system uses compressor oil AT41244 (ISO 150).
- The volume of refrigerant for filling the air conditioning system is 0.65 kg.
- Compressor oil volume: 0.22 l.
Figure 8-68. Air conditioner unit installation diagram:
1 - compressor;
2 - injection pipeline;
3 - low pressure pipeline;
4 - evaporator;
5 - high pressure pipeline;
6 - capacitor;
7 - receiver-dryer;
8 - condenser pipeline.
Condenser 6 of the air conditioner is aluminum. Condensation occurs in it (transition to liquid state) refrigerant pumped by the compressor with the release of heat into the atmosphere. For better airflow, the condenser is installed in front of the radiator of the cooling system.
Evaporator 4 is an aluminum heat exchanger. The transition of the refrigerant from a liquid to a gaseous state (evaporation) occurs in it with the absorption of heat. The evaporator is installed in the instrument panel on the path of the incoming air flow, which ensures a decrease in its temperature.
The receiver-dryer 7 is installed on the outlet pipeline of the condenser before the evaporator and serves as a reservoir for the liquid refrigerant, purifying it from foreign impurities and water. The receiver-dryer can be equipped with a viewing window to monitor the amount of refrigerant.
The thermostatic expansion valve is installed on the evaporator and regulates the amount of refrigerant entering the evaporator. The expansion valve is a device that ensures a change in the system's performance depending on the operating conditions and mode.
The pressure sensor sends a signal to the ECM to turn the air conditioner on/off depending on the pressure in the high-pressure line.