You may not realize it, but modern refrigerators don't only cool things down, they keep things from getting too cold. Yes, you guessed it: refrigerators have onboard heaters. They're low-wattage, but refrigerator heaters are very convenient and effective at doing everything from heating the evaporator coils to melt any accumulated frost, to keeping the butter chilled but not so cold that you'll need a chain saw to cut through it.
Gas and Propane Refrigerators
If you own an RV, chances are you have a gas- or propane-powered refrigerator. These refrigerators are interesting because they have no moving parts and use gas or propane as their primary energy source. Also, they use heat to produce the cold inside the refrigerator.
A gas refrigerator uses ammonia as the coolant, and water, ammonia and hydrogen gas to create a continuous cycle for the ammonia. The refrigerator has five main parts:
- Generator - creates ammonia gas
- Separator - separates the ammonia gas from water
- Condenser - where hot ammonia gas is cooled and condensed to create liquid ammonia
- Evaporator - where liquid ammonia converts to a gas to create cold temperatures inside the refrigerator
- Absorber - absorbs the ammonia gas in water
It works like this:
- Heat is applied to the ammonia and water solution in the generator. (The heat comes from burning gas, propane or kerosene.)
- As the mixture reaches the boiling point of ammonia, it flows into the separator.
- Ammonia gas flows upward into the condenser, dissipates heat and converts back to a liquid.
- The liquid ammonia makes its way to the evaporator where it mixes with hydrogen gas and evaporates, producing cold temperatures inside the refrigerator's cold box.
- The ammonia and hydrogen gases flow to the absorber where the water collected in the separator in step No. 2 mixes with the ammonia and hydrogen gases.
- The ammonia forms a solution with the water and releases the hydrogen gas, which flows back to the evaporator.
- The ammonia-and-water solution flows toward the generator to repeat the cycle.