270 



TEMPERATURE AND HUMIDITY 



vention of condensation. The tropics show 

 clearly the necessity for air conditioning and 

 the reduction of humidity. This was 

 demonstrated in the Pacific area in World 

 War II. 



The main reason can be stated very 

 simply. The human body is maintained at 

 a temperature of 37°C (98.6°F) and the 

 skin temperature is usually 2-5°C lower. 

 When the air temperature is as high as the 

 skin temperature the body is no longer able 

 to lose heat by radiation and convection and 

 must depend entirely on the evaporation of 

 sweat. If the humidity also is high there 

 is no longer efficient evaporation and the 

 heat produced in the body must be stored in 

 the body. This results in a rise of body 

 temperature, first to a point of discomfort, 

 then inefficiency, and finally death. 



Beneficial effects of air conditioning were 

 appreciated not only by the improvement of 

 living conditions but also in the avoidance 

 of condensation of water on electrical 

 equipment. The penalties of air condition- 

 ing are of course the weight, the bulk and 

 the noise. Efforts must be made to reduce 

 all three of these factors and there seem to 

 be great possibilities. Improvements can 

 be made in the apparatus itself. Some help 

 may be obtained by encouraging the con- 

 densation of water on the inner surface of 

 the hull. In the old submarines before 

 World War I there was a great deal of such 

 condensation but it was later eliminated by 

 the introduction of cork lagging. Even in 

 the tropics the sea water is several degrees 

 cooler than the human skin where the sweat 

 is vaporized. If the layer of cork lagging 

 were separated from parts of the hull by an 

 inch, and air were circulated through this 

 space, the air would come in contact with 

 metal almost as cool as the sea water. When 

 the temperature of the skin is37°C (98.6°F), 

 the saturated air in its immediate neighbor- 

 hood contains 43.5 grams of water per cubic 

 meter. If the inside of the hull were 30°C 

 (86°F) the saturated air at its surface would 

 contain 30.0 grams of water. This differ- 



ential would be large enough to reduce the 

 humidity without the penalty of weight or 

 noise. The reduction would not be great 

 but it would relieve some of the load on the 

 air conditioning apparatus and would be of 

 considerable service when silence was im- 

 perative. 



The chief advantage of separating the 

 lagging from the hull would be a continual 

 movement of cold air downward over the 

 inside of the hull even without the use of 

 blowers. This seems to be the only noiseless 

 method available. There are strenuous 

 objections to this idea on the part of sub- 

 marine designers and operating officers since 

 it would encroach on space and would lead 

 to rust. The method of running ventilating 

 pipes outboard under the superstructure 

 from one compartment to another would 

 cause great condensation of moisture but 

 would require the use of a noise-producing 

 blower. 



The attainment of even partial dehumidi- 

 fication by silent means will demand much 

 experimentation. It is well worth the time 

 and trouble if we can judge from the reports 

 of officers who commanded submarines in 

 the war zone of the tropics. They tell of 

 long submergences with sweat dripping so 

 fast that it filled their shoes and made 

 puddles on the deck. 



It must be remembered that the human 

 skin and lungs are not the only sources of 

 water vapor in a closed submarine. Vapor 

 from batteries and cooking contribute to the 

 load, and there may be methods of reducing 

 both of these without much penalty of 

 weight. 



It is impossible to emphasize too strongly 

 the fact that it is the vaporization of water 

 from the skin that is of vital importance in 

 regulating body temperature in hot environ- 

 ments. The dripping of sweat from the 

 body is of absolutely no help in losing heat. 

 It merely increases the loss of precious water 

 and salt from the body and eventually 

 leads to the serious picture of water and 

 salt deprivation. Drinking cold water helps 



