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DEW-POINT TEMPERATURE
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Figure 10-15.-Simplified psychometric chart. environment  vary,  the  body  automatically  regulates  the amount of heat that it gives off. However, the body’s ability to adjust to varying environmental conditions is limited. Furthermore, although the body may adjust to a  certain  (limited)  range  of  atmospheric  conditions,  it does  so  with  a  distinct  feeling  of  discomfort.  The discussion that follows will help you understand how atmospheric  conditions  affect  the  body’s  ability  to maintain a heat balance. Body Heat Gains The body gains heat by radiation, by convection, by conduction,   and   as   a   by-product   of   physiological processes  that  take  place  within  the  body. The  heat  gain  by  radiation   comes  from  our surroundings.  However,  heat  always  travels  from  areas of  higher  temperature  to  areas  of  lower  temperature. Therefore,  the  body  receives  heat  from  those surroundings that have a temperature higher than body surface  temperature.  The  greatest  source  of  heat radiation  is  the  sun.  Some  sources  of  indoor  heat radiation  are  heating  devices,  operating  machinery,  and hot  steam  piping. The  heat  gain  by  convection  comes  only  from currents of heated air. Such currents of air may come from a galley stove or an engine. The heat gain by conduction comes from objects with which the body comes in contact. Most body  heat comes from within the body itself. Heat  is  produced  continuously  inside  the  body  by  the oxidation of foodstuffs and other chemical processes, friction and tension within the muscle tissues, and other causes. Body Heat Losses There  are  two  types  of  body  heat  losses-loss  of sensible  heat  and  loss  of  latent  heat.  Sensible  heat  is given  off  by  radiation,  convection,  and  conduction. Latent heat is given off in the breath and by evaporation of  perspiration. EFFECT OF AIR MOTION In perfectly still air, the layer of air around a body absorbs the sensible heat given off by the body and 10-16






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