Design and evaluation of passive downdraft cooling systems: outcomes from built prototypes of single stage and hybrid downdraft cooling towers

Abstract

This research aims to advance performance of the single stage passive downdraft evaporative cooling tower (PDECT) and expand its applicability beyond the hot dry conditions where it is typically found by developing a design for a multi-stage passive and hybrid downdraft cooling tower (PHDCT). The proposed design cools the air entering the tower shaft in two stages, first using a sensible cooling stage and then using a direct evaporative cooling stage. Half-scale prototypes of these towers were built and tested in Tempe, Arizona during summer of 2017. Measurements were collected simultaneously from both towers to evaluate performance under identical conditions. Results indicated that the hybrid tower outperformed the single stage tower under hot dry conditions when sensible cooling was concurrently operating with evaporative cooling and fan. Additionally, it expanded applicability of downdraft cooling to hot humid conditions when sensible cooling and fan were operating without evaporative cooling.