Efficient and intense heat removal from a hot surface is of great importance in various engineering problems, such as nuclear power plant emergency cooling, continuous material casting processes, design of compact heat exchanges, etc. Spray cooling has been widely used in various industries and thermal management due to its convenience of use, low cost of operation, and more importantly high intensity of cooling rate. However, the conventional spray cooling process cannot reach its full potential until its shortcomings, i.e., inefficient utilization of coolant and non-uniform distribution of heat dissipation rates over a hot surface can be remedied. This research involves the use of electrostatically charged liquid sprays in the cooling process. Preliminary experiments conducted at the University of Illinois at Chicago revealed that electrically charged water droplets dissipate heat about 40% greater than the uncharged conventional case. In addition, various interesting effects of charged droplets were observed, i.e., increased critical heat flux (CHF), extended CHF temperature, and increased heat dissipation in the film boiling region of the coolant. Effects of charged droplets, namely, electric charge density, droplet size, droplet number density, liquid properties, and heater surface temperature are being investigated by both experimental and hybrid-analytical methods in this study. Using specially designed experimental apparatus and recently developed instruments, visualization tests of droplet impaction and heat transfer experiments will be performed. In the heat transfer experiments, two different boundary conditions for a hot surface, i.e., a transient surface temperature and a constant temperature boundary conditions, will be tested in order to see whether a boiling hysteresis exists in charged spray cooling heat transfer. In addition to the laboratory type of heat transfer experiment, real scaled experiments will be conducted by using commercially available electrostatic spray atomizers. All the information obtained through these tasks will serve as a sound data base for future development of an efficient and high intense cooling technique.
