Capillary Pipe Effects Too Long

Capillary Pipe Effects Too Long; Capillary tube is also called: Impedance tube, Restrictor tube or choke tube. The refrigerant rate control system in the simplest refrigeration system is a capillary tube. As the name suggests, the capillary tube consists of a pipe with a very small diameter. The diameter of the capillary tube is generally between 0.26 in to 0.4 inch depending on the size of the system capacity. Figure shows a refrigeration system with a capillary tube.

At a certain length and diameter, the capillary tube has a fairly high frictional resistance so that it can reduce high condensation pressures to low evaporation pressures. The capillary tube functions to regulate the amount of liquid refrigerant that enters the evaporator and to keep the pressure difference between the condensing pressure and the evaporation pressure constant.

Because the capillary tube is connected in series in the refrigeration system, the size of the liquid refrigerant distribution capacity produced by the capillary tube must be adjusted to the compression capacity of the compressor used. Therefore, to obtain high efficiency, the capacity of the capillary tube must be adjusted to the compression capacity of the compressor.

In the capillary tube there is a relationship between the diameter of the pipe and the length of the pipe to the frictional resistance of the refrigerant. Here is a description of the relationship.

1. The larger the diameter, the smaller the resistance.

2. The smaller the diameter, the greater the resistance.

3. The longer the capillary tube, the greater the resistance.

4. The shorter the capillary tube, the smaller the resistance.

Then what are the consequences if the capillary tube is too long or too short. Here's the explanation.

Consequences of Too Long Capillary Pipe

If the frictional resistance of the capillary tube is too large, because the capillary tube is too long or the diameter is too small, the capacity of the pipe to deliver liquid refrigerant from the condenser to the evaporator is smaller than the compression capacity. As a result, the evaporator lacks liquid refrigerant, the pressure will drop. On the other hand, the liquid refrigerant in the condenser increases, so the condensation pressure will also increase. This large condenser pressure makes the compressor work which will make the compressor overheat. This will shorten the compressor life.

Consequences of Too Short Capillary Tubes

On the other hand, if the frictional resistance of the capillary tube is too small, because the capillary tube is too short or the diameter is too large, then the capacity of the pipe to deliver liquid refrigerant from the condenser to the evaporator is greater than the compression capacity. As a result, the evaporator has an excess of liquid refrigerant, the pressure increases. Not all liquid refrigerant can evaporate in the evaporator. Liquid refrigerant will enter the compressor which can damage the compressor itself.

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