Abstract: A heat exchange device is disclosed in the form of a condenser for vapors containing non-condensible gases. Mechanical shutter members in the form of air foils are pivotally mounted in the exhaust stacks of the condenser for selectively blocking the exhaust stack to prevent back draft through the condenser when the respective air circulation fan thereof is inoperative. In one form of the invention, the condenser includes air recirculation ducts which also can be selectively closed by dampers to prevent back draft through the return ducts when the respective air recirculation fan is inoperative.

Abstract: A wet surface air cooling system is disclosed and includes a primary cooling unit having a bundle of heat exchanger tubes. Water is directed over the bundle of heat exchanger tubes and is collected in a collection basin. A secondary cooling tower is provided and a closed circulatory loop draws a portion of the water from the collection basin and directs the water to the secondary cooling tower to increase the cooling capacity of the system. The secondary cooling tower is rendered operative automatically upon sensing a particular temperature of the water in the circulation system of the primary cooling unit.