Feature selection and extraction

463,855. Unit air - cooler. HEATING VENTILATING & AIR CONDITIONING CO., Inc. Sept. 4, 1936, No. 24208. Convention date, Sept. 6, 1935. [Class 137] A fan 7 draws fresh air through a duct 8 and filter, and recirculated air through openings 14 and a filter 15, the air circulating through a spiral passage 6, the walls of which are cooled by a refrigerant in pipes 5, before issuing through the fan. A motor 18 has one shaft coupled to the fan spindle 20, and the other to a rotary compressor 21 which compresses the refrigerant before it passes by a pipe 26 to the condensing coils 27 which are cooled by air drawn through an inlet duct 37, and forced by a fan 23 around the coils to an outlet duct 35. The refrigerant, condensed to a liquid, flows into a tank 29 and passes by a pipe 32 through an expansion valve 34 to the cooling pipes 5, returning to the compressor by a pipe 25. The valve 34 is controlled by a thermostat (not shown).