Absorption System:
An absorption refrigerator is a
that uses a heat source (e.g.,
propane,solar,
kerosene-fueled flame, waste heat from factories or district heating
systems) to provide the energy needed to drive the cooling system. In
the early years of the twentieth century, the vapor absorption cycle
using water-ammonia systems was popular and widely used, but after the
development of the
vapor compression cycle it lost much of its importance because of
its low
coefficient of performance (about one fifth of that of the vapor
compression cycle). Nowadays, the vapor absorption cycle is used only
where waste heat is available or where heat is derived from
solar collectors. Absorption refrigerators are a popular alternative
to regular compressor refrigerators where electricity is unreliable,
costly, or unavailable, where noise from the compressor is problematic,
or where surplus heat is available (e.g., from turbine exhausts or
industrial processes, or from solar plants). For example, absorption
refrigerators powered by heat from the combustion of
liquefied petroleum gas - propane - are often used for food storage in
recreational vehicles and cabins, off
the grid dwellings - propane refrigerator Absorptive refrigeration can also be used to
air -condition buildings using the waste heat from a
gas turbine
or water heater.
This use is very efficient, since the gas turbine produces electricity,
hot water and air-conditioning (called
trigeneration).
Both absorption and compressor refrigerators use a refrigerant with a
very low boiling point (less than 0 °F (−18 °C)). In both types, when this
refrigerant evaporates (boils), it takes some heat away with it,
providing the cooling effect. The main difference between the two types
is the way the refrigerant is changed from a gas back into a liquid so
that the cycle can repeat. An absorption refrigerator changes the gas
back into a liquid using a different method that needs only heat, and
has no moving parts other than the refrigerant itself.
The other difference between the two types is the refrigerant used.
Compressor refrigerators typically use an
HCFC
or
HFC, while absorption refrigerators typically use
ammonia or water.
Absorptive refrigeration uses a source of heat to provide the energy needed to drive the cooling process. The absorption cooling cycle can be described in three phases: Evaporation: A liquid refrigerant evaporates in a low partial pressure environment, thus extracting heat from its surroundings – the refrigerator. Absorption: The gaseous refrigerant is absorbed – dissolved into another liquid - reducing its partial pressure in the evaporator and allowing more liquid to evaporate. Regeneration: The refrigerant-laden liquid is heated, causing the refrigerant to evaporate out. It is then condensed through a heat exchanger to replenish the supply of liquid refrigerant in the evaporator.
Propane Fuel Consumption
A typical 12 cubic foot propane refrigerator consumes an average 1.5 lbs. of propane per day, which works out to about 1,400 British thermal units of energy per hour or 32,225 BTU per day. Propane refrigerators are available as small as 4 cubic feet and as large as 18 cubic feet. Small units may consume well under 1 lb. of propane per day while large units may consume nearly 2 lbs. per day. Consumption also varies somewhat by brand. Running Time A standard 20 lb. propane bottle, widely available, provides 430,000 BTU of energy when full. At 32,225 BTU or 1.5 lbs. per day, that 20 lb. bottle will run your 12 cu. ft. propane refrigerator for 13 days. If you used two of these bottles, you would get around 26 days of running time. If you had access to larger propane bottles, you could run your typical 12 cu. ft. refrigerator far longer. A pair of 40 lb propane bottles would run your unit for 52 days, while a single 100 lb. bottle would run the appliance for 66 days.
Why Propane?
Propane Refrigerators running on propane or other fuels were introduced in the 1930s, when most of rural America lacked any electric service. Fuel-powered refrigerators are still being produced by a number of manufacturers for sale to the Amish and others who choose to live without electricit, and for remote hunting lodges and vacation cabins located far from power lines. For remote dwellings used only seasonally, propane refrigerators and other propane-powered appliances can be a viable alternative to bringing in electric power. How They Work A propane refrigerator uses a sealed piping system containing a mix of ammonia, water and hydrogen. The propane flame heats a boiler filled with an ammonia/water solution. The heated solution bubbles up through a percolator pump, releasing hot ammonia vapor and returning the water to the boiler. The ammonia vapor rises to a condenser where it transfers heat to the room air and turns back into liquid. The ammonia liquid drains down into an evaporator filled with hydrogen gas that reacts with the ammonia to vaporize it again, drawing the necessary heat energy from the interior of the refrigerator. This cools the box and contents. The ammonia-hydrogen mixture drains down to an absorber chamber where the ammonia re-dissolves in water, releasing the hydrogen gas to rise back up into the evaporator. The water-ammonia solution drains down into the boiler to continue the cooling cycle.
Venting
Although propane is a clean-burning fuel, without enough combustion air, the flame releases carbon monoxide. This gas is invisible, colorless and odorless; it bumps oxygen out of the blood, damages major organs and could kill you. Since propane refrigerator burners are tucked away in an enclosed space, the burners must be supplied with sufficient combustion air, and exhaust gases must be vented outside. To do this, enclose the burner in a vented box, and position the outside exhaust vent well above the air intake tube; this will force rising hot gases to suck cold air down to the burner.
How to turn on a Propane Refrigerator
1-Locate the propane/electric switch on your RV's refrigerator. This is usually located on a panel on the top edge of the refrigerator, although in some models you may find it at the bottom.
2- Set the switch to "propane." The switch may be a dial type switch that you turn from one setting to another or it may be a button that is pushed to activate the propane refrigeration system.
3- Push in and hold the button labeled "push to start." This will be located near or next to the propane/electric switch.
4- While holding in the button, press the "ignitor" button. Look into the viewing window or prism on the control panel for a flame. Press the ignitor again if you don't get a flame the first time. When you see the flame, continue holding in on the "push to start" button for 30 seconds, then release. Check to be sure the flame is still burning--if it isn't, repeat the process.
How to Burb Propane Refrigerators
1-Shut off the electricity and gas running to the refrigerator. Unscrew the connections to the gas and disconnect any wires.
2-Remove the screws holding the refrigerator in place. Remove the refrigerator from its compartment.
3-Place the refrigerator outside on level ground. Enroll the help of another person to avoid back injury.
4-Turn the refrigerator on its side and leave it for two hours. Listen to the refrigerator for the chemicals mixing together. Turn the refrigerator upside-down. Leave the refrigerator in this position for 24 hours.
5-Carry the refrigerator back into the RV. Secure the refrigerator back in its compartment. Hook up the electricity and gas lines.