Methods Thawing of evaporators for Air Cooling
The defrosting process that removes frost and ice from the surface of the evaporator to maintain optimum heat transfer rates. In cases where the evaporator surface temperature remains above the dew point of moisture in the air, liquid film forms on heat transfer surfaces. This layer of water improves the conduction of heat from the air to the refrigerant. Consequently, the die temperature of the air at coil outlet closer to die saturation temperature of the refrigerant dian would be if the coil were dry. With frost cannot form in these applications, defrost strategy is not required.
In many applications, the temperature falls below the dew point, as it passes through the evaporator surfaces. Consequendy, some moisture in the air condenses on heat transfer surfaces. If the water temperature falls below the freezing point, an insulating layer of frost forms on heat transfer surfaces. Frost reduces the intensity of heat exchange coil and the air flow rate, as it accumulates. In applications exposed to frost, a method of periodically thaw coil is required if the project efficiency of the process is to be maintained.
Capacity finned-tube evaporators more susceptible to frost accumulation than other types of evaporators. Therefore, when the battery coils operate at temperatures below 34 F (2.8C)some methods defrosting coil at regular intervals must be provided. This can be done automatically means, briefly described below.
Off-cycle defrost is used in cases, when the temperature in the Cabinet supported by the above 34F (2.8C) and frost accumulation die on the surface of the coil is minimal. Compressor periodically closed was off and die evaporator fans forced convection units are in operation. Warm air to the Cabinet gradually melts the frost off to die coil. The resulting condensate is collected in a pan down the evaporator and pipeline outside of the classroom...
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Evaporators