Heat pumps associated with reversibly used cooling towers present great potential for energy saving insubtropical areas. To study the heat and mass transfer characteristics of reversibly used cooling towerswith downward spraying (DSRUCT) and optimize its thermal performance, a mathematical model wasdeveloped and validated throughfield experiments. Then a parametric study was conducted to study theimpacts of initial solution temperature (4to1C), gas velocity (2.5e4 m/s), initial droplet velocity (4e10 m/s) and droplet diameter (0.65e1.2 mm) on the heat rate, tower effectiveness and solution tem-perature distribution. According to the results of the parametric study, we proposed an optimizationmethod established on the concepts of critical gas velocity and critical height. This method was based onmultivariable analysis. Two operating parameters (gas velocity and droplet diameter) and one structuralparameter (tower height) were simultaneously concerned. The results of this work provided a theoreticalfoundation for optimizing the thermal performance and saving initial investment of DSRUCT and othercounter-current spray systems, e.g., dehumidification, desulfurization, spray cooling, and carbon capture.
