Performance comparison and suitable climatic zones of three water-mediated evaporative cooling technologies

Evaporative cooling is an alternative cooling technology to conventional vapor-compression systems with lower energy use and pollution emissions. This paper presents theoretical performance comparison for three water mediated evaporative coolers and provides a design guideline for choosing evaporative coolers under specific climates and operating boundary conditions. Theoretical solutions of counter-flow evaporative cooling are given and verified with maximum absolute and relative errors of 0.26 K and 1.23% respectively. The heat transfer coefficient of the combined heat and mass transfer is 2.72-4.95 times than the pure heat transfer process if there were no mass transfer. Climatic dividing lines of various technologies are affected by the design parameters of the system, dropping the psychrometric chart into different applicable climatic areas. The simulation results show that the climatic areas in psychometrics where indirect outperforms direct evaporative cooling will expand when increasing the air-water ratio and heat transfer coefficient, and climatic area of series indirect evaporative cooling shrinks when increasing temperature difference. The simplified selection method using such difference in merits is verified by case study, which can serve as a useful guideline for choosing the proper evaporative cooling technology for a wide range of geographical locations.