Here is the technical data on how gas or heating
element-driven absorption systems cool your LP 'fridge or freezer.
The continuous absorption type of cooling unit is operated by the
application of a limited amount of heat furnished by gas, electricity or
kerosene. No moving parts are employed.
The unit consists of four parts: the boiler, condenser, evaporator
The unit can be run on either electricity, kerosene or gas. When the
unit operates on kerosene or gas, the heat is supplied by a burner which
is fitted underneath the central tube (A) and when the unit operates on
electricity, the heat is supplied by a heating element inserted in the
The unit charge consists of a quantity of ammonia, water and hydrogen
at a sufficient pressure to condense ammonia at the room temperature for
which the unit is designed.
here to see a really cool diagram of how it works!
When heat is supplied to the boiler system, bubbles of ammonia gas
are produced which rise and carry with them quantities of weak ammonia
solution through the siphon pump - C. This weak solution passes into the
tube (D), while the ammonia vapor passes into the vapor pipe (E), and on
to the water separator. Here any water vapor is condensed and runs back
to the boiler system, leaving the dry ammonia vapor to pass to the
Air circulating over the fins of the condenser removes heat from the
ammonia vapor to cause it to condense to liquid ammonia in which state
it flows into the evaporator.
The evaporator is supplied with hydrogen. The hydrogen passes across
the surface of the ammonia and lowers the ammonia vapor pressure
sufficiently to allow the liquid ammonia to evaporate. The evaporation
of the ammonia extracts heat from the evaporator, which in turn extracts
heat from the food storage space, as described above, thereby lowering
the temperature inside the refrigerator.
The mixture of ammonia and hydrogen vapor passes from the evaporator
to the absorber.
Entering the upper portion of the absorber is a continuous trickle of
weak ammonia solution fed by gravity from the tube (D). This weak
solution, flowing down through the absorber, comes in contact with the
mixed ammonia and hydrogen gases which readily absorbs the ammonia from
the mixture, leaving the hydrogen free to rise through the absorber coil
and to return to the evaporator. The hydrogen thus circulates
continuously between the absorber and the evaporator.
The strong ammonia solution produced in the absorber flows down to
the absorber vessel and from there to the boiler system, thus completing
the cycle of operation.
The liquid circulation of the unit is purely gravitational.
Heat is generated in the absorber by the process of absorption. This
heat must be dissipated into the surrounding air. Heat must also be
dissipated from the condenser in order to cool the ammonia vapor
sufficiently for it to liquefy. Free air circulation is therefore
necessary over the absorber and condenser.
The whole unit operates by the heat applied to the boiler system and
it is of paramount importance that this heat is kept within the
necessary limits and is properly applied.
not working? Check out this diagram to see the most common reasons for
cooling unit failure.