How Gas & Propane Refrigerators Work

Not every refrigerator requires electricity to keep food cool. Gas refrigerators and propane refrigerators are commonly used by campers who don't want to forego fresh food, or as occasional utilities for RVs or weekend fishing cabins. Here's how they work.

Refrigerating with gas, propane, or kerosene

A non-electric refrigerator keeps food cool through the application of heat to an interior coolant. This heat source is provided by burning gas, propane, or kerosene (some gas refrigerators can also be run on electricity). The coolant in gas and propane refrigerators is a mix of ammonia and water.

The refrigerant cycle in gas refrigerators uses six basic parts:

• a boiler
• a generator
• a separator
• a condenser
• an evaporator
• an absorber

The process begins when heat is applied to the generator via gas, propane, or kerosene fired in the boiler system. The generator's "unit charge" is a mix of ammonia and water. The applied heat brings ammonia to a boiling point, causing bubbles of ammonia gas to pass up through the separator. The separator does just that: it sends water vapor back into the boiler and permits the dry ammonia gas to enter the condenser.

A gas refrigerator's condenser is comprised of metal coils and fins. Air circulating over those fins cools the ammonia, transforming it into a liquid before it enters the evaporator.

The evaporator contains hydrogen gas. When mixed with the liquid ammonia, the hydrogen lowers the ammonia's vapor pressure to the point where it vaporizes/evaporates, producing a cooling effect inside the propane refrigerator as heat is drawn to the evaporator coils.

At this point gravity takes over. The ammonia/hydrogen mix flows down from the evaporator into the absorber. Remember when the ammonia bubbles went through the separator? Well, before they did, a little ammonia solution passed through a tube that led to the absorber. The result is that as the ammonia/hydrogen mix meets this ammonia that was siphoned off earlier, the hydrogen rises back up to the evaporator. The ammonia continues its downward course through the absorber and back into the boiler system.

For gas refrigerators and propane refrigerators to work well, it's important for them to have adequate air circulation. The heat drawn into the absorber from inside the refrigerator must be dissipated into the outside air. Following all manufacturer's instructions will help you get the most efficient use out of your gas refrigerator's boiler.