Gas and Propane Refrigerators 

How They Work 

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:

  1. Heat is applied to the ammonia and water solution in the generator. (The heat comes from burning gas, propane or kerosene.)
  2. As the mixture reaches the boiling point of ammonia, it flows into the separator.
  3. Ammonia gas flows upward into the condenser, dissipates heat and converts back to a liquid.
  4. 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.
  5. 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.
  6. The ammonia forms a solution with the water and releases the hydrogen gas, which flows back to the evaporator.
  7. The ammonia-and-water solution flows toward the generator to repeat the cycle.

How Does a Propane Fridge Work?

Unlike an electric refrigerator, which uses a coolant to keep the interior cold, a propane fridge relies on simple chemical reactions. The process starts with a flame fed by a propane tank, which is why this appliance is called a propane fridge.

Propane Flame

A propane fridge has a sealed network of tubes and chambers holding water, ammonia and hydrogen gas. A propane flame heats a chamber holding a solution of water and ammonia until the liquid boils. The ammonia gas rises to another chamber, the condenser, where it cools back into a liquid. It then flows to the evaporator, where it mixes with hydrogen gas.

Cooling Action

When ammonia encounters hydrogen gas, the chemical reaction between the two absorbs heat. That's how the propane fridge produces its cooling action -- by pulling heat from the interior of the refrigerator into the ammonia-hydrogen mix. As it absorbs heat, the ammonia becomes a gas again. The ammonia and hydrogen gases then combine with water. The ammonia and water form a solution again, which releases the hydrogen gas to rise back to the evaporator. The process then starts all over again.