When you say someone “runs hot and cold,” it isn't usually a
compliment. But if it's a propane refrigerator, running hot and cold is a very
good thing. Also known as an “absorption refrigerator,” the propane
refrigerator proves that you can use fire to make ice – and you can do it al
without electricity, or even moving parts.
The device is based
on some basic physics, first recognized by scientist Michael Faraday in 1828,
when he liquefied ammonia gas and mixed it with silver chloride powder. As the
ammonia evaporated, the mixture grew colder and colder – and the seeds of
modern refrigeration took root. Thirty years later, French scientist Ferdinand
Carre would combine water and sulphuric acid and get similar results, and by
the 1920's, a century after Faraday's observation, the first commercially
produced propane refrigerators were on the market.
The appliance operates on a system of heat, pressure,
evaporation and condensation, with liquids and gases moving from chamber to
chamber. Propane provides the heat source, which boils distilled water an
ammonia mixture until the two ingredients separate. In the distilling process,
the ammonia, which is lighter, is pushed upward into the condenser, while the
water is pushed back down into the mixture's original tank.
In the condenser, as it moves onward, the ammonia becomes a
rich liquid and flows into the evaporator tube system, where it meets the
compressed hydrogen gas that is rising to meet it. When the hydrogen and
ammonia meet, a chemical reaction occurs. The ammonia evaporates, and in the
process, absorbs the heat in in the refrigerator.
The propane refrigerator is a closed system, with sealed
compartments and no moving parts. This means, for all practical purposes, that
the process must be based on a cycle, endlessly repeating itself. The cold
ammonia mist that was the result of its reaction with the hydrogen flows
downward, mixing with the water in the tank to begin the process all over
again.
The space needed for the tubes and cambers can limit the
space of an absorption refrigerator, compared to an electric, but the lack of
moving arts such as motorized compressors, make the propane appliance virtually
maintenance free. Keeping dust, lint and other debris away from the burner
vents is essential to smooth operation, and if the model has a flue, it needs
to be cleaned on a regular basis. Because the flow of water, ammonia and
hydrogen is essential to the operation of the device, the propane refrigerator
should be kept as level as possible.
The units can take up to 24 hours to cool, so it's a good
idea to start the refrigerator up a day before it is stocked, and keep in mind
that of the seals aren't sealing, the refrigerator will not be operating at
maximum efficiency.
Most problems that pop up on the troubleshooting lists don't
involve the unit so much as they do the heat source. The propane tank needs to
be kept at about 80 percent capacity to allow room for expansion, than lines
and connectors need to be checked regularly for leaks. The air in the lines
should be bled out before lighting, and the area around the burner kept free of
dust and lint.
Absorption refrigerators don't necessarily require propane.
Butane, kerosene, batteries, even refuse can be burned to provide the initial
heat source. Industrial plants often use their incinerators as the heat source
for their cooling system. Because electricity is not required, the propane
refrigerator can continue to operate when the power goes out, making it a
valuable asset in times of natural disaster, or a convenient one in situations
or locations where electricity is not available, too expensive, or simply not
wanted.
The propane
refrigerators come in many sizes, from massive units that cool
manufacturing facilities, to smaller ones tucked away in the rolling kitchens
of recreational vehicles. Prices tend to be higher than electric refrigerators
when it comes to start up. For instance, a basic 64-inch tall propane
refrigerator with 7.9 cubic feet capacity costs approximately small electric
“dorm” refrigerator can run from $1,500-2,500, where an electric one of
comparable size costs about $400. Depending on where you live, the cost of
running a propane fridge ranges from 50- 80 cents a day. Because the absorption
refrigerator can use other heat sources, including natural gas, that operation
cost can vary, and even compete with the $4-5 a month operating cost of an
electric unit, especially if you live in an area where gas prices are low and electricity
is high.
But the lack of moving parts decreases the amount – and cost
– of maintenance, and as technology improves, the propane water heaters are
becoming more efficient, another factor that will increase their desirability
and affordability. Besides offering the social maverick a way to live “off the
grid” and still keep his food supply cold, the propane refrigerator offers a
healthy cooling source for food when natural disasters strike and the grid
itself goes down.
