How Do Electronic Ignitions in Refrigerators Work?
- Refrigerators that use ignition are called absorption refrigerators. They are not the most common type. Most refrigerators use an electronic pump to circulate the coolant and cool food. These refrigerators are much more efficient when electricity is available. Absorption refrigerators are very useful when you don't have access to electricity, or when there is a lot of waste heat to use. They are used in camping because they can easily be run off a propane burner. As an added bonus, they are almost completely silent.
- The electronic ignition makes a spark, which lights a pilot light. When the refrigerator warms past a certain point, the pilot lights the main propane burner. The heat from that propane is used to heat a mixture of water and ammonia in the part of the refrigerator called the generator. This mixture is heated until the ammonia bubbles out as ammonia gas. Once the ammonia bubbles out of the water and cools down a bit, it becomes a liquid again in the condenser, where it is free of water. It loses heat and is ready for the evaporator.
- At room temperature, ammonia is a gas, but the high pressure in the refrigerator makes it remain a liquid until it is heated by the generator. However, once it enters the next component, the evaporator, the ammonia is put in a chamber with hydrogen gas. Because the ammonia only generates part of the pressure in the chamber, it acts as if it is in a low-pressure environment: It evaporates. When the ammonia evaporates, it absorbs heat, cooling down the evaporator. This is what causes the cooling in absorption refrigerators.
- While ammonia mixes easily with water, hydrogen does not. The absorber trickles cool water into the ammonia/hydrogen mixture, causing the ammonia to be absorbed in the water. The absorber trickles down into the generator. This starts the whole process all over again.
