Page:Popular Science Monthly Volume 88.djvu/922

 894

��Popular Science Monthly

��As in other machines, the motor is started and stopped by means of a

���This machine has a rotary compressor and

employs ethyl chloride as a circulating

refrigerant

thermostat in the refrigerator. The weight of this machine complete, in- cluding the brine tank, is about i6o pounds.

In recent years much has been done towards the development of an absorp- tion household -machine, and several meritorious machines of this type are now on the market. An absorption machine is much like the compression machine, the principal difference being that the compressor is replaced by a still or boiler. This still is partially filled with strong aqua ammonia. When heat is applied to the still the dissolved ammonia is driven off as a gas into the condenser, where it is converted into liquid ammonia just as in the compres- sion machine. After all the ammonia is driven off from the still and collected in the condenser, the burner under the still is extinguished and the still, with the water from the aqua ammonia, is allowed to cool down. Cold water has a great affinity for ammonia and at once begins to take up gas from the liquid ammonia which flows from the con-

��denser into the refriger- ating-coils. This evapo- ration of liquid ammonia in the refrigerator coils causes intense cooling.' Check valves are placed between the still and condenser and between the refrigerator-coil and still so as to make the ammonia flow in the proper direction. Of course there is no cooling done during the distillation period, but this period is generally very short compared with the absorption period. -Usually one distillation a day is sufficient. One great advantage of this is that there are no moving parts and hence no noise. The flow of the fuel gas and cooling water is automatically controlled in the later machines. The automatic devices will need some attention to keep them in order, especially the check- valves. The principal objection to these absorption machines is the high tempera- tures and pressures used. The alternate heating and cooling of the still tends to

���' ' B a rsm i t h liquid," which is similar to sulphur-dioxide, is the refrigerant used in this com- pact machine

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