Plant Types - Refrigeration Cycle
Plant Types - Refrigeration Cycle
Air conditioning = relies primarily on the refrigeration cycle which originally used a fluid called FREON
Freon = from the chorofluorocarbon or CFC gases family
Excerpts from USGBC article "Greening your Refrigerants — Saving the ozone layer and saving money"
"Under the Montreal Protocol U.S. CFC production ceased in 1995. Consequently, specification of non-CFC building equipment is now standard and CFC-based refrigerants are no longer available in new equipment... ...A common alternative to CFC refrigerants is their chemical cousin, hydrochlorofluorocarbons (HCFCs)... ...they still cause significant ozone damage... ...HCFCs will be phased out in the United States by 2030... ...hydrofluorocarbons (HFCs), that are considered "greener" than either CFCs or HCFCs. A key chemical difference is their absence of chlorine atoms, which means their ozone depletion potential is essentially zero. On the downside, they still have significant global warming potentials (like CFCs) and are somewhat less thermodynamically efficient than their predecessors..."
General description
Gases ar circulated in a closed, pressurized tubing loop, Pressure is varied by a pump and a constricted section of tubing or a valve, causing changes in temp., evaporation and condensation.
Condensor = Pump increases pressure on the gas, causing condensation, releasing latent heat of evaporation
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Evaporator = gas passes through an expansion valve(or constriction in the tubing) and experiences a pressure drop on downstream side allowing the liquid to evaporate, absorbing the latent heat of evaporation from its surroundings.
Due to extreme pressure differences, Condensation creates a high temp. and loses heat to it's surroundings and Evaporation creates a very low temp. absorbing heat from its surroundings.
Heat exchanger coils (like car radiator) = both evaporator and condensor are made up of them
evaporative chiller / cooling tower = located outside building and dissapates heated water from the condenser to the outside air, there is a constant loss of water which must be added
blow down = valve in base of cooling tower which allows minerals and dirt to be drained out for cleaning
Evaporator cycle / cooling loop:
coil takes heat from water or air down to 50 - 55deg F, then circulated around buliding.
Outside air may be used directly when cool enough.
cold clean pond water may be used in some climates instead of chilled refrigerated water cooling without the evaporative chiller, know as economizer cycle.
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