Gas and kerosene refrigerators have no moving parts. They use a heat source instead of a compressor to make the inside of the refrigerator cold. Some refrigerators also have optional electric back-up heaters that can be used if gas or kerosene is not available.
There are three significant benefits:
- No moving parts means no mechanical wear and tear
- Silent operation; no vibration, no motors
- No electric needed for reliable, consistent refrigeration
What’s inside a non-electric refrigerator?
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Gas and kerosene refrigerators use a mixture of water, ammonia and hydrogen to create a continuous cooling cycle. The mixture is pressurized so that the ammonia stays in liquid form when it’s at room temperature. The refrigerator has five main parts:
- Generator or "boiler" – generates ammonia gas
- Separator – separates ammonia gas from water
- Condenser – where hot ammonia gas is cooled and condensed to create liquid ammonia
- Evaporator – where liquid ammonia evaporates to create cold temperatures inside the refrigerator
- Absorber – absorbs the ammonia gas in water
How a non-electric refrigerator works
Heat provides the energy needed to produce pure liquid ammonia.
- Heat is applied to the generator/boiler.
- There is a mixture of ammonia and water in the generator/boiler. The ammonia boils at a lower temperature than water and begins to bubble. The bubbles carry a mixture of ammonia gas, liquid ammonia, steam and water up through the pump (C), just the way a coffee percolator works.
- The liquid ammonia and water bubbles out of the top of the pump and then flows back down to the generator/boiler (D). The nearly pure ammonia vapor continues to flow (E) up to the water separator where any remaining water condenses and drips back down to the generator/boiler.
- The pure, dry ammonia gas now flows onward to the condenser. The condenser is made of metal coils covered with cooling fins that remove heat from the ammonia gas, which then condenses back into liquid ammonia. This pure ammonia liquid flows downward into the evaporator.
Mixing pure ammonia and pure hydrogen produces a cooling reaction: Evaporation
- In the evaporator, the ammonia mixes with hydrogen gas. Contact with the hydrogen lowers the ammonia pressure enough that the liquid ammonia evaporates. Evaporation is a cooling process, and it is this step that produces the cold temperatures we need inside the refrigerator.
- The mixture of ammonia and hydrogen gas continues to flow downward into the absorber, where the water has pooled.
- In the absorber, water and ammonia rapidly combine. This is because the polarity of the ammonia molecule makes it "eager" to combine with H2O. We say the water "absorbs" the ammonia. As a result, the hydrogen gas is released, and it floats back up to the evaporator where the cooling cycle can be repeated.
- The heavy water and ammonia liquid runs back down into the boiler where it can be heated again to continue the cycle.
The complete cycle of liquid and vapor circulation relies only on the pull of gravity. For that reason, the refrigerator must be kept level.
During the cooling process, heat is released into the room. Most gas refrigerators require 1"-2" clearances behind the unit and 6" above the unit to allow for air circulation.