n it; to accomplish this, coils ran
round the space filled with cold brine, which, as it grew warm, drew the
heat from the air. The brine in turn circulated through a tank
containing pipes filled with ammonia vapour which extracted the heat
from it; the brine then was ready to circulate through the coils in the
hold again and extract more heat. The heat-extracting or cooling power
of the ammonia is exerted continually by the process described below.
Ammonia requires heat to expand and turn into vapour, and this heat it
extracts from the substance surrounding it. In this marine refrigerating
machine the ammonia got the heat from the brine in the tank, then it was
drawn by a pump from the pipes in the tank, compressed by a power
compressor, and forced into a second coil. The second coil is called a
condenser because the vapour was there condensed into a fluid again.
Over the pipes of the condenser cool water dripped constantly and
carried off the heat in the ammonia vapour inside the coils and so
condensed it into a fluid again--just as cold condenses steam into
water. The compressor-pump then forced the fluid, ammonia through a
small pipe from the condenser coils to the cooling coils in the tank of
brine. The pipes of the cooling coils are much larger than those of the
condenser, and as the fluid ammonia is forced in a fine spray into these
large pipes and the pressure is relieved it expands or boils into the
larger volume of vapour and in so doing extracts heat from the brine.
The pump draws the heated vapour out, the compressor makes it dense, and
the coils over which the cool water flows condenses it into fluid again,
and so the circuit continues--through cooler, pump, compressor, and
condenser, back into the cooling-tank.

In the meantime, the cold brine is being pumped through the pipes in the
hold of the ship, where it extracts the heat from the air and the rows
of sides of beef and then returns to the cooling-tank. In the
refrigerating plant, then, of the supply-ship, there were two
heat-extracting circuits, one of ammonia and the other of brine. Brine
is used because it freezes at a very low temperature and continues to
flow when unsalted water would be frozen solid. The ammonia is not used
direct in the pipes in a big space like the hold of a ship, because so
much of it would be required, and then there is always danger of the
exposed pipes being broken and the dangerous fumes released.

Opposite as it may seem