Difference Between Thermostatic Expansion Valve and Capillary Tube

A thermostatic expansion valve is a complex device that adjusts refrigerant flow based on the system’s cooling load.

In contrast, a capillary tube is a simple fixed-length expansion device that has the advantage of allowing bidirectional communication.

These expansion valves are used in the refrigeration unit and air conditioning system. Still, the way they flow refrigerant is different.

Let’s learn the difference between a Thermostatic Expansion Valve and a Capillary Tube.

Learn the difference before, you learn what is a thermostatic expansion valve and what is a capillary tube.

1. Efficiency

Whether the system needs a giant or smaller heat load, a thermostatic expansion valve can constantly adjust mass refrigerant flow to the changing demand to adapt to the temperature fluctuation.

A thermostatic expansion valve can benefit the cooling system by improving efficiency. In contrast, a capillary tube can’t provide additional efficiency.

Please read how an expansion valve works to better understand the structure.

2. Wide range of temperature

We know that liquid slugging can harm a compressor unit, but when a thermal expansion valve raises the refrigerant flow, ensure the cooling system can go with the increased temperature, saving your compressor from damage.

A capillary tube expansion valve has a smaller temperature range than a thermal expansion valve.

3. Budget

The capillary tube is super simple in design with no moving parts, so its cost is lower than a thermostatic expansion valve.

There are many types of expansion valves, which provides you with more choices, and you can check out more Types of Expansion Valves here.

4. Service & Maintenance Cost:

The simple design allows a capillary valve to get damaged less than other expansion valve types.

Still, a TXV has more moving parts and a complex design that should be costly for repair or replacement.

A simple structure makes the price low, complex structure makes the price high.

Please read What is Expansion Valve to better understand why capillary tubes are less expensive.

5. Response Time

The thermostatic expansion valve can adjust the refrigerant flow in time according to the superheat at the outlet of the booster.

Therefore its response time is shorter.

Capillary expansion valves do not have this function.

The superheat and subcooling of the capillary tube are already designed at the factory (this is related to the length and diameter of the capillary tube).

Therefore, it cannot adjust to superheating or subcooling.

This is the most significant disadvantage of a capillary tube expansion compared to a TXV.

A TXV can respond quickly to the refrigerant flow and adjust the temperature for better cooling or heating.

Several scientific studies show that the coefficient of performance (COP) of a thermal expansion valve is higher than that of a capillary valve.

Though a capillary valve is also used in some application tube optimization, it is not a widely used expansion valve as a static option.

It can’t go with a changing ambient temperature.

TXV application experiences 20% less downtime and 10% less energy consumption than an application that uses a capillary tube expansion valve.

Learn more from your HUBHVACR expansion valve expert. Contact us now for your free quote.

Related Products: Thermostatic expansion valve, Danfoss expansion valve, Emerson expansion valve, etc.

6. Application

In addition to the structure, price, efficiency, and other differences, there is a big difference in that they have different applications.

Capillary expansion valves can be used in cooling and heating equipment because they are bi-directional. For example, water chillers.

It is mainly used for small refrigeration equipment, such as indoor condensing units, self-contained refrigeration units, drop-in refrigeration units, remote condensing units, and so on. etc.

The application range of thermostatic expansion valves is wider, it is used in cold room refrigeration units, outdoor condensing units, semi-hermetic refrigeration units, commercial refrigeration units, etc.

6. Comparison

Thermostatic Expansion ValvesCapillary tube
Is an expansion valveIt is a thin tube used for expansion.
It is used in large refrigerant capacity systems.It is used in Small refrigerant capacity system
The pressure Drop is High.The pressure Drop is Low.
Efficiency is highEfficiency is low.
Cost is highThe cost is low.
Receiver is requiredThe receiver is not required
The starting torque of the motor driving compressor is high.The starting torque of the motor driving compressor is Low
Complicated construction.Simple construction

Recommended Reading

Difference Between Thermostatic Expansion Valve and Electronic Expansion Valve

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