Their uses generally are to condense steam, to cool heated gases, air,
or articles of food requiring a low temperature; distilling, and other
purposes. For cooling purposes, compressed air machines are in most
demand. The air is compressed in a cylinder, then cooled to ordinary
temperature again in a surface condenser, such as No. 468, and then
expanded into the cooling chamber, through a cylinder and piston, the
expansion reducing its temperature usually to 10° or 20° below zero.
Other cooling appliances are ammonia machines, fans, and blowers of all
kinds, punkahs, or waving fans, freezing mixtures, &c.
=467. Gravity condenser.= The pipe should be 34 feet high or more, in
which case no air pump is required, as the condensed steam and air are
discharged below. In place of the pipe an air pump and foot valve are
required, and are commonly used, as it is seldom convenient to have a
vertical pipe 34 feet long with a water supply at the top.
=468. Surface condenser, multitubular.= The steam may be led into the
tubes, and the water around them, or _vice versâ_.
=469. Worm, or coil condenser,= chiefly used for distilling.
=470. Still condenser for essences,= spirits, &c.
=471. Condensing chambers for gases,= &c. Horizontal or vertical.
=472. Wimshurst’s condenser,= requires no air pump. The exhaust comes
down the vertical pipe, meeting the injection water from the side
nozzle, causing sudden condensation and vacuum. The condensed water,
&c., are blown out through the foot valves at each stroke.
=473. Another form of ejector condenser= in which the steam and water
form a vacuum in the nozzle, and the water, &c., are discharged through
a foot valve (not shown).
=474. Tray cooler, or condenser;= a series of water trays supplied from
a tank above.
See Morton’s ejector condenser, which requires no air pump; Hayward’s
exhaust condenser, which employs the water in suction pipe of a
pumping engine to condense the steam. See Messrs. Tangye’s list. Water
tube cooling coils are used for tuyeres and other hot surfaces.
Air-compressing and gas engine cylinders are water jacketed to carry
off the heat of the compressed air or gas. Cooling by exposing a large
surface to air is sometimes employed for exhaust steam on tram car
engines &c., the apparatus consisting generally of numerous
wrought-iron tubes or coils.