No_2_November_and_December__1948 — Page 43

THE HONG KONG AND FAR EAST builder

41

THE MOTORLESS REFRIGERATOR.

By L. G. W. GREEN

Today there are two types of automatic refrigerators. The earlier is a mechanical or motor-driven refrigerator. The newer is the modern motorless refrigerator. These two different types may be termed the "mechanical" method and the "natural" method.

Any form of power that turns a shaft could be used to operate a mechanical refrigerator. But electric motors are used instead of water wheels or gasoline engines be- cause electricity has proved to be the most convenient form of automatically controlled power for the average city home.

In the same way, any form of heat can be used to operate a motorless refrigerator. Gas and electricity are preferred for the average city home because these have proved to be the most convenient forms of automatically controlled heat. However, in remote districts where these two heating elements are not available, kerosene can be used.

The advantages of the motorless refrigeration system arise from its silence and the complete absence of moving parts in the freezing system.

Whether energized by gas in the silent motorless re- frigeration system, or by electricity in the mechanical system, the principle is the same. The refrigerant is re- duced to a liquid (in a condenser) then expanded to a vapor. As the liquid refrigerant expands into a vapor, it absorbs the heat of the food compartment, thus cooling the cabinet and the food. The refrigerant may be ammonia, Bulphur dioxide, freon or other liquids which have suitable boiling and freezing points.

Both types of refrigerators use the refrigerant over and over again, automatically. The motor-driven type draws the refrigerant vapor from the evaporator by using motors, compressors, pistons, valves and other moving parts. In the motorless refrigerator, the refrigerant is reclaimed for continuous use simply by absorbing it in dis- tilled water which is permanently sealed in the system.

In one method a solution of ammonia and water is heated in a chamber called the "generator" or "vaporizer".

The ammonia vaporizes, and leaves the water because of its lower boiling point.

The ammonia vapor then rises to a series of tubes known as the "condenser," air passing over fins cools the ammonia vapor, and the pressure in the system changes it to ammonia liquid.

The ammonia liquid flows by means of gravity into the coils of the freezing unit. Here, in the presence of hydrogen, which eliminates any need for a valve, the am- monia liquid evaporates. In making this physical change, heat is withdrawn from the interior of the frozen food storage compartment, cooling the food and freezing the water in the ice cube trays resting on the coils.

The evaporated ammonia mixes with the hydrogen, and this mixture, being heavier than pure hydrogen alone. sinks by gravity to the cooling coils of the general food compartment. The mixture already contains some am- monia vapor, and therefore does not absorb as much heat as it does in the frozen food storage compartment, thus maintaining a safe but not freezing temperature between 33° and 50°. The hydrogen and ammonia mixture then sinks to another series of coils known as the "absorber".

Meanwhile, the water in the "generator" or "vaporizer" is raised by a simple coffee percolator action to the "separa- tor" as the ammonia vapor is being driven off. The water then flows to the absorber through the mixture of hydrogen and ammonia. Ammonia has an affinity for water-that is, it will be absorbed or dissolved in water and form a solu- tion of ammonia and water. Hydrogen, on the other hand, is not absorbed by water. Being very light, the hydrogen returns to the freezing unit where it does its work again.

Finally, the ammonia and water solution flows by means of gravity back to the generator, where it is again heated and the cycle continues-a never-ceasing process that produces constant cold, steady refrigeration. The advantages of the motorless system are quietness in opera- tion, no lubrication required as there are no moving parts and finally the simplicity of the system which should en- sure long life and freedom from breakdowns.

DOTRA

ROOS

EVAPORATOR

HYDROGEN RESERVE VESSEL

FOOD SPACE

GAS HEAT

EXCHANGER

ABSORBER

RECTWER

MALYZER

LIQUID HEAT EXCHANGER

GENERATOR

CONDENSER