Calculating Infiltration and Ventilation Heat Gain
It has been shown that outdoor air enters a structure by means of both infiltration and ventilation. Because air is composed of a mix- ture of dry air and moisture particles, the heat gain produced by the entering air will be expressed in terms of both its sensible heat gain and its latent heat gain in Btu per hour.
The sensible and latent heat gain resulting from entering air rep- resents only a small portion of the total heat gain involved in deter- mining the design cooling load of a structure. For many applications, however, the calculation of this portion of the heat gain is crucial to a well-designed system. The following formulas, adapted from ASHRAE materials, are used for making these calculations:
In order to use these formulas, it is first essential to determine the outdoor and indoor design conditions (that is, the dry-bulb and wet-bulb temperatures) and the maximum rate of entering air (in cubic feet per minute).