Significance of parameters affecting the performance of a passive down-draft evaporative cooling (PDEC) tower with a spray system

•It demonstrates the significance of main parameters including those have not been well treated in the literature.•It presents practical design guidelines for main parameters so as to significantly improve the performance of the system.•It ensures that the performance of the system varies with many factors, rather than one dominant factor.•It formulates two mathematical models that predict outlet air temperature and velocity.