How does hot gas defrost affect the refrigerant flow in the evaporator?

Hot gas defrost is a method used primarily in refrigeration systems to remove ice or frost buildup from the evaporator coils. During this process, hot refrigerant gas, instead of the typical cold refrigerant, is directed into the evaporator. This gas is at a higher temperature and is capable of melting the frost or ice that has accumulated on the evaporator coils.

When hot gas is introduced into the evaporator, it significantly changes the typical flow direction of the refrigerant. Instead of allowing the refrigerant to flow continuously in the regular cycle—where it absorbs heat from the evaporator and moves towards the compressor—the hot gas defrost session requires the refrigerant to flow in reverse. This change in direction ensures that the hot gas effectively warms the evaporator and facilitates the defrosting process.

In summary, hot gas defrost allows the system to temporarily reverse the normal flow of refrigerant in the evaporator to effectively remove frost or ice buildup, thereby maintaining the efficiency and functionality of the refrigeration system.