Experts in advanced refrigeration and air-conditioning

Discharge line in refrigeration and air conditioning

The discharge line is one of the basic concepts in everything related to compressors, as well as refrigeration and air conditioning systems. So now we will talk about a part that is present in all circuits in both fields and that every refrigeration technician should fully understand. To be more precise, we will talk about its function, and also about how important it is for the correct functioning of the aforementioned parts. We will also highlight its great importance for the performance of a circuit and an appliance.

The function of the discharge line is to transport the superheated high-pressure steam from the compressor discharge valve to the condenser inlet.

What is the discharge line?

To define what the discharge line is, we can look at its function, which can be summarised as being responsible for transporting the high pressure, superheated steam from the compressor discharge valve to the condenser inlet. The discharge line is also known as the hot gas line. The discharge line is responsible for removing superheat by cooling the vapours that have been superheated by the compressor. It also ensures that this heat is transferred to the atmosphere.

The compressed vapour has accumulated all the heat that has been absorbed by the evaporator, and by the suction line. The heat added throughout the compressor pumping process must also be taken into account. Furthermore, there also is the heat that is generated in the movement of the motor, which must also be conducted to the discharge line. Taking into account the large amount of heat that accumulates on both sides, the discharge line thus becomes the hottest part of the whole system. It is therefore very important that the condenser is not dirty, because in these cases – as well as on very hot days – the temperature can exceed 200ºC.

The discharge line is essential: since by preventing the refrigerant from superheating, the vapours are cooled to the saturation temperature of the condenser. When this step occurs, the vapours will reach the condensation and saturation temperature indicated for that pressure, and condensation of the vapour will take place as more heat is lost. If the refrigerant line pipes are not the correct size and do not correspond to the amount of vapour or liquid for which they were designed, loss of refrigerant pressure may occur. This has negative effects on the subcooling of a liquid line, and means the expansion valve is unable to work properly. This can lead to additional problems in the compressors and the evaporator.

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