Air cooling evaporators
Air cooling evaporators for storefronts, coldrooms, blast freezers and air conditioners have finned tubes in coils (see Fig. 7.1). In all but very small coolers, such as domestic and small commercial units will be fans blow air through the heat exchanger.
Construction materials are the same as for air-cooled condensers. Aluminium plate, copper pipes are the most common for halocarbons, stainless steel or aluminium, pipes for ammonia. Frost or in the form of a condensate on the fin surface and must be drained away. To allow this, slats vertical and air flow horizontally, with drain tray provided in the framework.
The size of the tube will be such that the speed of boiling liquids in it can lead to turbulence, to encourage the transfer of heat. Pipe diameter will vary from 9 mm to 32 mm, depending on the size of the coil.
Fin pitch will be a compromise between compactness (and cost) and trend Interfin gaps in the quarter from condensed moisture and frost. Step will vary from 2 mm on CD conditioner to 12 mm low-temperature refrigerated areas of the coil.
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Evaporators 