Friday, November 30, 2012

Natural Gas Refrigerators

Refrigerators use similar basic concepts, whether powered by electricity or by fossil fuels like natural gas. Both approaches cool storage spaces with a sealed heat exchange system that circulates a liquid refrigerant. When the refrigerant boils, the change to vapor robs heat from the local environment, dropping the refrigerated compartment's temperature. Electric systems control a refrigerant by mechanical compression, but gas-powered refrigerators use absorption refrigeration, a method that works without a noisy compressor.


Propane Refrigerator, Natural Gas Refrigerator EZ Freeze 15
cubic foot capacity home style refrigerator freezer.
Video shows 360 degree view of inside and out,
 cooling system, burner box and flue.
Different liquids boil and change to vapor at different temperatures. Boiling points also change with pressure. Water, for example, boils at a lower temperature as altitude increases. Other liquids such as freon or ammonia boil at much lower temperatures than water. Even if a liquid boils at a temperature near freezing, the refrigerant absorbs energy from its cold environment as it changes to vapor.
Refrigerant coils boil refrigerants under low pressure inside the cold storage compartment, absorbing heat. Hot vapor moves into a different coil, under higher pressure, to condense back to liquid and shed heat into the outside air. To keep coolant circulating, an electric refrigerator uses a compressor to force liquid refrigerant into the evaporator or cooling coil.
Gas-powered, or absorption, refrigerators use a liquid to absorb and circulate the refrigerant. In many absorption refrigerators, water acts as the absorbent and ammonia becomes the refrigerant. Recirculating ammonia vapors dissolve in the water within an absorption chamber, releasing heat. The water and ammonia mixture travels to a generator tank. Gas flame heats steam coils inside the tank to evaporate the ammonia from the water. Cooling stages condense the ammonia vapor into pure liquid ammonia, the system's refrigerant. Water circulates back to the absorption compartment.
In the evaporator coil located in the walls of the refrigeration compartment, the liquid ammonia boils and ammonia vapor collects heat. Hot ammonia vapor circulates through an expansion valve into the higher pressure condenser coil. In the condenser coil, the hot vapor exchanges heat with the air flowing over the outside of the sealed metal tubing. Cooling ammonia flows back to the absorption chamber. Both the condenser coil and the absorption chamber vent heat to the outside air. If the system can't shed the excess heat because of dirty coils or lack of ventilation, the cooling effect stops. (eHow)

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