A rule of thumb for direct evaporative coolers (desert coolers) has be
en evolved in terms of the size of the poor area to be cooled for two
different climates, namely hot dry and composite, typified by Jodhpur
and Delhi, respectively. Linear relations have been obtained to evalua
te the cooler size for the space to be cooled in order to reduce the d
iscomfort index of the building by 90% of its value without a desert c
ooler.