The typical response of an engineer to a man working in a heat stress environment is to cool the environment. There are, however, some situations in which it is not feasible or economic to cool the environment. The alternative is to ignore the environment and to cool the man - that is individual cooling.

Individual cooling can be done by conduction, convection, or evaporation of water (generally sweat). Taking them in reverse order, cooling by evaporation of sweat and convection typically is done by blowing air over the man. The increased velocity of the ambient air improves evaporation and, if the air temperature is less than the body's, the heat load is reduced by convection also. Another option is to blow cooled air. Still another option is the blowing of cooled air with lowered humidity.

Bitterly describes a technique of cooling an astronaut by evaporation only, with one of the unique features being that the water evaporated is furnished by the cooling system rather than the sweat of the body.

This paper will describe cooling by still another technique, conduction; more specifically, conduction cooling by cold water in tubes. Containing the water in a tube allowed the water to be reused and permitted a less sloppy environment although some heat transfer capability was lost because of the tube. A liquid was used in the tube rather than a gas because, as shown by Burton, a liquid has 1,000 to 2,000 times the heat transfer· capabilityfor the same pumping energy requirement. Once a liquid was decided .on, water was the natutal choice due to its low cost, availability-and high specific heat.