6.87 VI.10.2: Solar Heat Gain - Sensible and Latent Heat: The precise value of the design heat gain is difficult to assess. Earth normal practice requires the designer to sum all worst cases and size the system to handle the extreme case. This approach would lead to serious oversizing of the air conditioning system of the prototype due to cyclical variations in heat load components. This study simplified the problem by setting the design heat gain rate equal to the sum of electrical power demand, sunlight energy, and power necessary to control the colony's temperature and humidity: Pinputtotal Pinputsunlight + Pinputelectrical 2.79xl0 7 watts+ 5.6xl0 6 watts+ Pthermal 3.35xl0 7 watts+ Pthermal This sum is the average daylight demand. Section VI.8 discussed numerous means to remove waste energy from the colony. Passive radiation (Section VI.8.3) could remove more than twice the heat needed if the temperature of the outer hull was brought equal to that of the inner hull. The extreme sensitivity of this value to changes in outer hull temperature should be noted: should the surface temperature drop to 248°K, the energy flow would be cut in half. The final configuration expects some heat flow from inner to outer hull: conduction takes place along bulkheads, radiation across compartments, and convection across compartments since they contain an atmosphere. The magnitude of this energy flow depends on the effective overall thermal conductivity of the double-hull. Humidity control, however, is dependent solely on processes interior to the colony and will be discussed next. In order to determine demand for dehumidification, the heat gain generated in the colony must be divided into sensible and latent heat components. Sensible heat gain is that portion of
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