- ABSTRACT: A multi-stage down-draft evaporative cool tower (DECT) was developed as an improvement to an existing single-stage design. The new tower incorporates a secondary air inlet, added to increase the cooling output and reduce the water consumption in a tower of given crosssection and primary inlet geometry. The secondary air, which may be drawn from the interior space being cooled, is cooled by evaporation in the lower section of the tower. This paper reports on the results of experiments conducted to establish the aerodynamic performance of the design prior to installation of a water spraying system. Design of the water spraying system and experiments on cooling performance are discussed in a companion paper.