A propane refrigerator or propane freezer use the heat generated from burning propane to provide cooling for the appliance. This sounds counter-intuitive, but it is made possible by the use of absorption refrigeration technology.
Many people are familiar with LPG - liquefied petroleum gas - from experiences using propane heaters and propane cookers. However, the use of propane to cool with a water, ammonia and hydrogen mixture is less wide spread.
The functioning of an absorption refrigerator is rather complex, so I will only explore it briefly here. Below is a description of the cooling cycle in one of these propane fridge freezers.
The burning propane is used to heat a pressurized burner unit. This compartment contains a combination of water and liquid ammonia. The flame boils this mix, and it then bubbles into another unit referred to as the separator.
In the separator, the ammonia gas is separated from the water and in turn passed on to a section of the apparatus referred to as the condenser. In a propane fridges condenser, cooling finds cool the ammonia gas which causes it to convert back to pure liquid ammonia.
Once cooled the liquid ammonia continues on to the propane refrigerators evaporator unit. Here the liquid ammonia combines with hydrogen gas, resulting in the pressure of the ammonia dropping. The end result of this is that the ammonia once again changes phase to a gas by evaporating.
Because this evaporation absorbs heat, it results in a net cooling in the compartment. This cooling is what refrigerates the appliance. After evaporation the gaseous ammonia moves on to an absorber unit. There is recombines with liquid water and finally goes back to the boiler, where the entire process starts again.
One important point to keep in mind about propane refrigerators and propane freezers is that they must be kept level. The chief reason for this that in the absence of any moving parts a large part of the mechanism for the absorption cycle depends entirely upon gravity. If everything is not completely level some of these flows can be disrupted.
The lack of moving parts is also a positive feature of a propane refrigerator of propane freezer. They are very reliable due to lacking any moving mechanisms that can suffer from wear. They are also very quiet and run without operation, chiefly due to the absence of any kind of motor in the refrigerator.
One cautionary note is to be sure to adequately ventilate any propane fridge freezer. The absorption cycle used for the refrigeration generates a lot of excess heat, and adequate air flow is a must to allow the heat to safely dissipate.
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