The thermal performance of evaporative coolers and condensers can be p
redicted theoretically by solving a system of coupled nonlinear differ
ential equations. All numerical solutions of this system of equations
proposed in the literature are too complex for practical application.
Known analytical solutions, based on different simplifying assumptions
, may cause large errors of up to 40% in the predicted heat load. Corr
elations have been developed for a new design method which allow to es
timate the errors of the most simple analytical solution as functions
of dimensionless operating parameters. With errors of less than 12% fo
r coolers and 10% for condensers respectively the new method leads to
far more accurate results than the analytical solutions.