How does a truck's air conditioning system work?

The commercial vehicle air conditioning system is actually a relatively independent system, with a low degree of association with other automotive systems. Therefore, even if a fault occurs, troubleshooting is relatively simple.

Air conditioning structure

Commercial vehicle air conditioning has three main components, the compressor, condenser, evaporator, and a host of other ancillary components, including expansion valves, liquid storage dryers, piping, condensing fans, blowers, temperature sensing packages, and so on.

Functions of the main components

The compressor is driven by the engine through a belt. Its function is to suck in low-temperature and low-pressure refrigerant vapor, compress it to the required pressure, and then send it to the condenser. It is the power source of the entire air conditioning refrigerant circulation. The higher the engine speed, the faster the refrigerant circulation, and the greater the cooling capacity.

The condenser's function is to transfer the heat of the high-temperature and high-pressure refrigerant gas to the outside air, causing the refrigerant to condense into a liquid. The condensation effect of the condenser directly determines the refrigeration efficiency of the air conditioning system. There are usually three methods to improve the condensation effect: 1. Increase the flow of air passing through the condenser; 2. Reduce the temperature of the air passing through the condenser; 3. Keep the surface of the condenser clean and free of contaminants.

The evaporator is usually arranged in the cab, and its function is to absorb heat from the cab, so that the liquid refrigerant absorbs heat and vaporizes into gas.

The main functions of the liquid storage dryer in an air conditioning system are: filtering, drying, dehumidifying and storing excess refrigerant.

Expansion valve and temperature sensing package are usually installed on the evaporator, and the temperature sensing package is usually located at the outlet of the evaporator to detect the outlet temperature of the evaporator and automatically adjust the opening of the expansion valve to control the flow rate of the refrigerant to control the stability of the temperature in the cab.

How refrigeration works

When the compressor is running, it sucks in the low-temperature and low-pressure refrigerant vapor generated in the evaporator and compresses it. The compressed refrigerant is then discharged into the condenser in a high-temperature and high-pressure state. The condenser fan cools down the refrigerant, and the cooled liquid refrigerant flows from the bottom of the condenser into the receiver-dryer.

After removing water and impurities, the pure refrigerant is throttled and cooled by the expansion valve. The low temperature and low pressure liquid refrigerant flows into the evaporator to absorb heat and achieve cooling. The cold air is blown into the cabin through the blower, reducing the temperature inside the cabin. The gaseous refrigerant is then sucked back into the compressor after passing through the evaporator, and the heat in the cabin is transferred to the outside through this cycle.

The core principle of air conditioning refrigeration is that the refrigerant liquefies and releases heat in the condenser, and vaporizes and absorbs heat in the evaporator. The above is a simple explanation of the important components and refrigeration principles of the air conditioning system. Only by understanding the structure and principles of air conditioning can drivers better judge the cause of air conditioning failures.