How does an automatic expansion valve work?

Asked By: Melaine Iando | Last Updated: 28th March, 2020
Category: home and garden indoor environmental quality
4.5/5 (578 Views . 28 Votes)
The automatic expansion valve (AXV or AEV) is an expansion device that meters the refrigerant to the evaporator by using a pressure-sensing device. The AXV maintains a constant pressure in the evaporator. When the tension is increased, the valve will feed more refrigerant and increase the suction pressure.

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Simply so, how does an expansion valve work?

Expansion Valve. The expansion valve removes pressure from the liquid refrigerant to allow expansion or change of state from a liquid to a vapor in the evaporator. The liquid refrigerant leaving the expansion valve is quite cold. The orifice within the valve does not remove heat, but only reduces pressure.

Furthermore, what is the function of expansion valve in refrigeration? A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV, or TX valve) is a component in refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator thereby keeping superheat, that is, the difference between the current refrigerant

Keeping this in view, which constant parameter is maintained in automatic expansion valve?

Constant Pressure Expansion Valve or Automatic Expansion Valve. The constant pressure expansion valve keeps the pressure inside the evaporator constant, hence the name. The constant pressure valve maintains constant pressure inside the evaporator no matter what the load inside the evaporator is.

What is expansion device in refrigeration?

REFRIGERATION AND AIR CONDITIONING. An expansion device is essentially a restriction offering resistance to flow so that pressure drops, resulting in throttling process.

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How do you test an expansion valve?

How to Test an AC Expansion Valve
  1. Make sure the AC unit is plugged in or, if it is in an automobile, turn the vehicle on.
  2. Use the manual to locate the thermostatic expansion valve.
  3. Lift the sensing bulb from the suction bulb well.
  4. Hold the sensing bulb in your hands for two minutes or place it in warm water.

How do you diagnose a bad expansion valve?

Symptoms of a Bad or Failing Expansion Valve (Orifice Tube)
  1. AC system performing worse than usual and blowing warm air. One of the first symptoms of a problem with the AC expansion valve or orifice tube is an underperforming AC system.
  2. Frost on AC evaporator or coming from the vents.
  3. AC compressor constantly running.

How do you adjust an expansion valve?

To adjust the static superheat, turn the valve's setting stem. Turning clockwise increases static superheat and effectively reduces refrigerant flow through the valve. Turning counterclockwise reduces static superheat and increases refrigerant flow.

What causes an expansion valve to freeze?

Bad Thermal Expansion Valve
Another reason for frozen lines in an AC unit is due to a faulty thermal expansion valve, also known as a TXV. This controls the flow of refrigerant through your AC unit. If this malfunctions then not enough refrigerant will pass through the system and the coils. That will cause a freeze up.

Where is the AC expansion valve located?


TXV Location
The thermostatic expansion valve is usually mounted inline with the tube that supplies liquid coolant to the air conditioner evaporator. The bulb of the expansion valve is mounted to the outside of the output line of the air conditioner evaporator.

Can a expansion valve be cleaned?

In these cases, it is far more beneficial to the customer if the valve is replaced instead of cleaned. It is very difficult to determine if a Thermostat Expansion Valve is clean. Any debris or contamination at the TXV can prevent proper flow of lubricating oil through the system and its return to the compressor.

What is the function of evaporator?

An evaporator is a device in a process used to turn the liquid form of a chemical substance such as water into its gaseous-form/vapor. The liquid is evaporated, or vaporized, into a gas form of the targeted substance in that process.

How does the automatic expansion valve respond to a load increase?

When the tension is increased, the valve will feed more refrigerant and increase the suction pressure. The AXV responds differently than the TXV to load changes. It actually acts in reverse. When a load is added to the coil, the suction pressure starts to rise.

Which of the following would allow a system to operate more efficiently?


64 Cards in this Set
When a system with a water-cooled condenser cycles off, the water regulating valve should ________. Close, since the head pressure is lower
Which of the following would allow the system to operate more efficiently? Condensers that have refrigerant leaving with 15 degrees of subcooling

What is hand expansion valve?

The hand expansion valve is normally used as a supplementary safety valve installed in a bypass line. It is also commonly used to control the flow rate through oil bleeder lines.

What is AXV?

The AXV is a constant pressure regulator. It is designed and constructed to maintain a constant evaporating pressure. The flow of the refrigerant into the evaporator is based on the pressure of the refrigerant in the evaporator.

What is a high side float?

High Side Float
The float is located on the high pressure side of the system and is operated by the liquid refrigerant level coming from the condenser. The High Side Float allows liquid refrigerant to flow into the evaporator at the same rate that refrigerant is being condensed.

What is low side float valve?

The low side float type of the throttling valve is usually used in the flooded type of the refrigeration plants. The float valve maintains the constant level of the liquid in the flooded evaporator irrespective of the pressure and the temperature inside it.

What is the function of capillary tube in air conditioning?


The air conditioning system or refrigeration system capillary tube, like the TEVs and AEVs and other devices discussed here, is a simple refrigerant liquid metering device which regulates the flow of refrigerant from the incoming high pressure side (from the compressor/condenser) into the low pressure side (in the

What happens to the refrigerant as it passes through the metering device?

What happens to the refrigerant as it passes through the metering device? The refrigerant drops in pressure and temperature as it passes through the metering device. A small portion of the refrigerant flashes to a vapor, cooling the remaining liquid.

What determines the amount of refrigerant that flows through a capillary tube?

What determines the amount of refrigerant that flows through a capillary tube metering device ? The difference in pressure from the inlet to the outlet and the diameter and length of the tube.