The continuous absorption type of cooling unit is oper-
ated 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 main parts—the boiler, con-
denser, evaporator and absorber.
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 tted underneath
the central tube (A) and when the unit operates on
electricity the heat is supplied by a heating element
inserted in the pocket (B).
The unit charge consists of a quantity of ammonia, wa-
ter and hydrogen at a sufcient pressure to condense
ammonia at the room temperature for which the unit is
designed.
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 into the
boiler system leaving the dry ammonia vapor to pass
to the condenser.
Air circulating over the ns of the condenser removes
heat from the ammonia vapor to cause it to condense
to liquid ammonia in which state it ows into the
evaporator.
The evaporator is supplied with hydrogen. The hy-
drogen passes across the surface of the ammonia
and lowers the ammonia vapor pressure sufciently to
allow the liquid ammonia to evaporate. The evapora-
tion of the ammonia extracts heat from the evapora-
tor 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 tub (D). This weak solution, owing
down through the absorber, comes into contact with
the mixed ammonia and hydrogen gases which read-
ily 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 absorb-
er ows down to the absorber vessel and then to the
boiler system, thus completing the full cycle of opera-
tion.
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 sur-
rounding air. Heat must also be dissipated from the
condenser in order to cool the ammonia vapor suf-
ciently 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.
The Absorption System
© Dometic 2007 OS2177 MKTGCOMM
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