Abstract: Recuperative heat exchangers are disposed in the supply and exhaust ducts of a ventilating system. To reduce frost build-up at the exit end of the exhaust-duct heat exchanger, the heat exchanger is disposed so that the exhaust air flows through it alternately from one end to the other, and vice-versa, when the temperature is below freezing. The reversal of flow of the exhaust air is accompanied by a reversal of the flow of heat exchange medium so that the efficiency of heat exchange is not adversely affected. Several systems of heat exchange are disclosed.

Abstract: A room air conditioning apparatus for exchanging heat and/or moisture between fresh atmospheric air entering the room from the outside and consumed air being discharged from the room combines high capacity with relatively small dimensions, low air velocities and small pressure drops so as to minimize generation of disturbing noise. Within a casing, a motor-driven regenerative-type rotor passes through two air stream zones in the first of which is a motor-driven fan for discharge of consumed room air into the outer atmosphere and in the second of which is a motor-driven fan for supply of fresh air to the room from the outer atmosphere. In the rotor, the two air streams exchange heat and/or moisture content so that the supply of fresh air is given a desired, predetermined temperature and a desired moisture content.

Abstract: A method of operating recuperative heat exchange means in the supply and exhaust ducts of a ventilation installation exposed to sub-freezing atmospheric condition so that the heat exchanger in the exhaust duct is allowed to ice up and is periodically defrosted. The method operates to control the temperature in the spent-air heat exchanger in various ways, including raising the input temperature of the the exchange medium to reduce the cooling effect on the spent air, or by reducing the flow of heat exchange medium to achieve the same result.

Abstract: An air conditioning system for conditioning air in a plurality of enclosed areas in a building. Conditioned air at a temperature level which may be varied is supplied to first terminal means for discharge into an area. Conditioned air at a relatively constant temperature level is delivered to second terminal means for discharge into the area. The quantity of constant temperature air discharged into the area is regulated in accordance with the temperature level therein. When the temperature of the variable temperature air supply is at a relatively warm level, the quantity thereof discharged into the area is regulated in accordance with the quantity of constant temperature air discharged into the area. As the quantity of constant temperature air discharged into the room is increased, the quantity of warm air discharged into the room is decreased; and as the quantity of constant temperature air discharged into the room is decreased, the quantity of warm air discharged into the room is increased.

Abstract: An air conditioning system for conditioning air in a plurality of enclosed areas in a building. Conditioned air at a relatively cold temperature level is supplied to a terminal for discharge into an area. The quantity of relatively cold temperature air discharged into the area is regulated in accordance with the temperature level therein. A control signal is generated, the magnitude thereof being indicative of the quantity of conditioned air discharged into the area. The magnitude of the control signal is monitored. Warm air supply means is activated when the magnitude of the control signal indicates that the quantity of the relatively cold temperature air being discharged into the area has decreased below a predetermined level.