Estimating the performance of natural draft evaporative coolers

In relatively arid regions, natural draft evaporative coolers can be used for cooling residential and commercial buildings, as well as outdoor areas, however, their design can be time consuming. Several approximations are presented here to simplify the computations. Density calculations are eliminated using a correction term with wet and dry-bulb temperatures. Under calm conditions, iterative calculations involving the pad air velocity and efficiency can be eliminated with a logarithmic approximation.