The flow of refrigerant through the TXV system is very similar to the flow through the orifice tube system. The refrigerant is the substance that flows through the components, which is used to absorb heat from the passenger compartment and carry it outside the cab and release it at the condenser to the outside air. Here is a step-by-step description of the refrigerant flow through a TXV system:
1. The compressor pulls in low-pressure refrigerant gas from the suction line and compresses it to raise the pressure and temperature. The refrigerant exits the compressor as a high-pressure gas.
2. The refrigerant is routed to the condenser through the discharge line. The refrigerant enters the condenser as a heated high-pressure gas. Airflow through the condenser fins causes the refrigerant to cool down, which causes the gas to condense into a liquid. The refrigerant exits the condenser as a hot high-pressure liquid. The temperature of the liquid is typically 20 to 50 degrees cooler at the exit than it was on entry of the condenser.
3. The refrigerant enters the receiver dryer as a warm high-pressure liquid. The receiver dryer stores and dries the refrigerant and prevents any gaseous refrigerant from being sent to the TXV. The exit point is at the bottom of the receiver dryer to ensure that only liquid is able to leave the receiver dryer. There should not be any temperature drop across the receiver dryer.
4. The refrigerant is routed to the TXV through the liquid line as a high-pressure liquid. The TXV acts as a restriction, which causes the pressure and temperature to drop and the refrigerant exits the TXV as a low-pressure, atomized liquid.
5. The refrigerant enters the evaporator core as a cool low-pressure atomized liquid. Duct box air is routed through the fins of the evaporator core, which causes the liquid refrigerant to begin to vaporize into a gas. This process of latent heat of evaporation absorbs the heat from the duct box air, which causes the air to be cool and dry as it exits the evaporator fins. The refrigerant exits the evaporator core as a low-pressure gas and is directed to the compressor as a cold low-pressure gas.
It is helpful to learn to understand the flow of refrigerant as it passes through each section of the AC system. The low side of the AC system runs from the exit of the TXV up to the entry point of the compressor. The high side of the AC system runs from the compressor exit up to the entry point of the