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TEMPERATURES
Body Heat Gains

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Figure  1O-13.-A  standard  sling  Psychrometer. Figure 10-14.-Exposed view of motorized psychrometer. When the air is saturated, all three temperatures are the same. By  using  both  the  wet-bulb  and  the  dry-bulb temperature readings, you can find the relative humidity and  the  dew-point  temperature  on  a  psychometric  chart (fig, 10-15). DEW-POINT TEMPERATURE.– The wet-bulb temperature  lines  are  angled  across  the  chart  (see  fig. 10-15). The dew-point temperature lines are straight across  the  chart  (indicated  by  the  arrows  for  wet  bulb and dew point). Find where the wet-bulb and dry-bulb lines  cross,  interpolate  the  relative  humidity  from  the nearest humidity lines to the temperature-line crossing point. Then, to find the dew point, follow the straight dew-point  line  closest  to  the  intersection  across  to  the right of the chart and read the dew-point temperature. For example, find the wet-bulb temperature of 70°F. Next, trace the line angling down to the right to the dry-bulb  temperature  of  95°F.  Finally,  to  find  the dew-point   temperature,   follow   the   dew-point temperature lines nearest the intersection straight across to the right of the chart. The dew-point line falls about one-third of the way between the 55°F mark and the 60° mark. You can see that the dew-point temperature is about  57°F. RELATIVE  HUMIDITY.–  To find the relative humidity  (see  fig.  10-  15),  first  find  the  dry-bulb temperature. Read across the bottom, find 95°F and follow straight up to the intersection of the wet- and dry-bulb readings. The relative humidity arc nearest the intersection is 30 percent. However, the intersecting line is below 30 percent and higher than 20 percent. You can see that the relative humidity is about 28 percent. BODY  HEAT  BALANCE Ordinarily, the body remains at a fairly constant temperature of 98.6°F. It is important to maintain this body temperature. Since there is a continuous heat gain from  internal  body  processes,  there  must  be  a continuous loss to maintain body heat balance. Excess heat must be absorbed by the surrounding air or lost by radiation.  As  the  temperature  and  humidity  of  the 10-15






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