Dry Expansion Evaporator
Dry-expansion of the refrigerant feed describes a strategy in which the amount of fluid is served in the evaporator is limited diat quantity which can be completely vaporized by the time of the refrigerant reaches die suction evaporator end. This method ensures diat refrigerant in the gaseous state, when it is in the suction line. The metering device at work with such way of submission of refrigerant or thermostatic expansion valve (TXV) or capillary tube.
To ensure complete evaporation of the refrigerant in the evaporator, the refrigerant in a dry-expansion of the supply system can become overheated. To prevent overheating of the loss of the liquid in the suction line. Therefore, the temperature on the surface of dry expansion evaporator always low input where flash-cooled liquid refrigerant vapor mixture comes to die coil. In most applications, die system is calibrated resolution about 10F (12.2C) overheating be added to the refrigerant. To achieve this level of overheating, from 10 to 20% of the surface of the evaporator area is used for transmission of the sensible heat to refrigerant vapor.
Remember, though saturation temperature die refrigerant below, at coil outlet due to the differential pressure, the temperature of the surface of the evaporator is always the highest in this place a dry-expansion applications.
Dry-expansion evaporators most popular type of heat transfer coils used in mechanical refrigeration. They are simpler in design, more compact and require less refrigerant and have less problems with oil return, and are cheaper than flooded or refrigerant circulates evaporators.