What is expansion valve? Types of expansion valve?

What is expansion valve? Type of expansion valve?


Expansion valves are the devices used to control of refrigerant flow. They help ease the high pressure change in liquid condensation in the density unit below the reinforced gas refrigerant in evaporation.

The term low side is used to indicate part of the system that acts under low pressure, in this case evaporator.

High side is used to indicate part of the system that work under high pressure, in this case the condenser.

Expansion valve is connected between liquid line and evaporator coile.
Type of expansion valve?

1.thermostatic expansion


The thermostatic expansion valve uses the system to control the flow of liquid condensation in evaporator coil.


The flow is controlled by pressure in the evaporator. This type of expansion valve devices can work well when the load fluctuates and therefore is suitable for use in the air conditioning system.

When the evaporator heat the valve, the high flow rate gives when it cools down, it reduces the rate of flow it is also generally referred to as TXV,TEV or TX valve.

There is a sensing bulb that detects the coil temperature and is usually located at high temperature inside the evaporator. To ensure proper sensing bulb must be clamped on the suction line.

When the temperature of the evaporator increases due to the demand for cooling, the pressure in the bulb also increase so that the spring forced to open the expansion valve.

When the temperature of the evaporator decrease due to lack of cooling demand, the bulb pressure will snap so that the spring causes the expansion valve close.

2. Float valve


The float valve start with the floating float in the liquid refrigerant. Low side float valve and upper side float valve are used to control the flow of liquid refrigerant.

The lower side float valve is helps to maintain continues levels of liquid condensation in the evaporator coil. Its opens when there is no liquid in externality .and when the vapor is liquid, its closes.

The upper side is located next to the high pressure system of the float and keeps the condenser continuously in the refrigerant.

 When the compressor is operated, the condensed refrigerant flows into the float chamber and opens the valve.

This divides the refrigerant into evaporator where it is stored. As the liquid level comes in the float chamber, the valve will prevent the opening of the trail to turn the flow towards evaporator.

3. Capillary tube


Capillary tube is a tube with a small inner diameter and can coil for its length. It is installed on the after liquid line.

Drier or filter is used before the capillary tube to remove dirt or moisture from the refrigerant.

This device is easy,  is not a moving part and lasts for a long time. To use this device, the amount of refrigerant in the system at the factory level should be properly calibrated.

Due to its lower cost then thermostatic expansion valve, these metering devices are used in units that are produced in large quantity such as a room air conditioning, windows air conditioning, water cooler or domestic used.

Depending on the capacity design of the system, the inner diameter of the capillary tube is usually used in a range of 0.031” to 0.065” and the outer diameter is 0.083” to 0.130”.

4. Automatic expansion valve


 The automatic expansion valve controls the flow of refrigerant in the evaporator from the liquid line, which uses pressure activated curtains.

It maintain constant pressure in evaporator coil. The shock is that it is not efficient if the load fluctuates is not suitable for use in this type of air conditioning units, because the load fluctuates during its operation.

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