The basis of design of the normal air conditioning system for any compartment or group of compartments is the removal of sufficient heat and moisture to maintain a reasonable standard of bodily comfort for the personnel to carry out their duties. The heat generated or 'heat load' as it is called, arises from four sources:
a. The men in the compartment.
b. Machinery, electrical apparatus, lighting, etc. in the compartment.
c. Conduction through the boundaries of the compartments from adjacent compartments,from the sun and from the sea.
d. Fresh air which has to be cooled from outside air temperature to the compartment temperature.
The outside air temperature is assumed to be 31°C DB/27°C WB for tropical conditions and 34°C DB/30°C WB for extreme tropical. The maximum acceptable temperature within the compartment is taken as 30°C DB/22°C WB unless otherwise stated in the design requirements. The total heat load is calculated using standard formulae to obtain the quantity of air required. The capacity of the plant is then chosen to suit this heat load and after grouping of compartments the task of deciding the sizes of fans, coolers and layout of trunking can proceed.
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