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Technical information Air-Conditioning Refrigerating System. Air and gas coolers

Refrigerating Systems. Air coolers and gas

These devices are called, as a rule, direct expansion coil and consist of a series of pipes, which flows refrigerant (Fig. 3.21). Tubes, finned, to increase the speed of transfer of heat from the cooling medium (e.g. air) to the boiling point, usually located in a number of parallel chains of feed from one of the throttle valve. Hot refrigerant vapor accumulate in the socket (suction) gas header. These direct expansion coil are only used in piston compressor systems, because of the fairly low pressure factors. As liquid coolers, these devices are also classified as flooded and dry type. In a flooded reel, a float valve is used to maintain a given level in the coil, maintaining the evaporator close to full liquid refrigerant. This is a complete contact of liquid with walls of the tube provides high heat transfer rate. In practical applications, flooded evaporators type are preferable because they require large amounts of refrigerant. Dry coil requires only a small amount of refrigerant, and this reduces the cost of refueling.

Sometimes a metering device (the expansion valve regulates the amount of water inside the coil to maintain a specified number of the superheat of refrigerant vapour at the outlet of the coil. Dry expansion coil contains mainly the liquid at the inlet and only superheated steam outlet, after absorbing heat from the medium to be cooled. In coolers of air, when the surface temperature drops below 0VC, glaze happens. A thick layer of frost act as insulation and reduce air consumption (in forced convection in rolls) and the room itself.

There are several methods to defrost, for example. hot-gas defrost and thawing of water. But recently frost-free refrigeration systems have become popular because of the problems mentioned above.

ABO-evaporator

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