What You Need to Know About Thermostatic Expansion Valves

October 12, 2021
Thermostatic Valve in Belleville, ON

A thermostatic expansion valve, also referred to as TXV, is a throttling device used in refrigerators and air conditioners to control the amount of refrigerant injected into the evaporator. This relies on the temperature and pressure of the evaporator, known as the superheat.

The TXV works through precision to regulate the flow rate of the liquid refrigerant. This is essential in increasing the efficiency of the evaporator and ensuring that excess refrigerant doesn’t flood back into the compressor.

The valve’s design feature forms a separation between the high- and low-pressure sides in an air conditioning system. Typically, the liquid refrigerant enters the valve through the liquid line under high pressure but phases a reduction in pressure when the amount of refrigerant flowing into the evaporator is minimized by the TXV.

Understanding the Function of the TXV

The thermostatic expansion valve works to control the refrigerant flow rate into the evaporator. It does not influence the capacity, suction pressure, air temperature, or humidity of the refrigerant since doing so would lead to the compromised performance of the system and possible failure of the compressor.

As it works to regulate the flow of the refrigerant into the evaporator, it ensures a steady supply of the refrigerant while matching the flow rate against how fast the refrigerant boils off within the evaporator coil. For this to happen, the valve responds to two variables: the temperature of refrigerant vapor as it exits the evaporator and the pressure within the evaporator. It utilizes a flexible valve pin against the spring to precisely regulate the refrigerant flow into the evaporator.

How the TXV Transfers Energy

As the flow of refrigerant is restricted, its pressure drastically reduces. A small amount of the liquid refrigerant undergoes a phase change and is converted to gas. The flash gas represents an intense degree of energy transfer through the conversion of the sensible heat of the refrigerant into latent heat.

Finally, the vapor combination and liquid of low pressure are directed into the evaporator, where the remaining liquid refrigerant evaporates, absorbing heat from the surroundings. Overall, this is how the TXV ensures precise control of the refrigerant flow in response to systematic conditions.

At Quinte Air Supply, we specialize in residential cooling, heating, indoor air quality, and water heater services in Belleville and the surrounding areas. We also assist with commercial refrigeration projects. Contact us today for more information or to set up an appointment.

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