STYDY ON HEAT TRANSFER CHARACTERISTICS OF SUCCESSIVE DROPLET TRAINS IMPACTING ON SILLICION SURFACE

With the development of electronic devices towards multifunctionality and miniaturization, spray cooling is still a highly effective cooling method in high heat flux thermal management. Important parameters of spray such as droplet diameter, quantity and velocity etc. are unpredictable due to the considerable variation in manufacturing standards and working conditions. To achieve a predictable spray, a droplet generator was self-designed and fabricated. It can produce a large number of predictable monodisperse controlled droplets depending on the setting frequency f_G. The experiments used deionized water as the cooling fluid. The droplets generated by the droplet generator is captured by a high-speed camera, which ensures that the droplets are uniformly broken up according to the Plateau-Rayleigh instability. The heating element is based on a silicon base, deposited with chromium and platinum by physical vapor deposition (PVD), and then combined through gold wire bonding. In the cooling area, the temperature field was investigated by IR thermal imaging techniques through a reflective path. Heat transfer characteristics of controllable droplet trains were experimentally conducted from single-phase to two-phase. The number of droplet trains is from 5*5 square-arrayed droplet train to 14*14 square-arrayed droplet trains, corresponding to droplet flux range is from N = 140750 1/cm²s to N = 2044280 1/cm²s. There are two factors affecting heat transfer performance, one is volumetric flow flux, and the other is the droplet flux. Compared to relatively low droplet flux, heat transfer studies revealed that more dense spray has significantly higher heat transfer coefficients and uniformity. This study is based on the thermodynamic analysis of controllable successive droplet trains, which is beneficial for the further application of controlled spray.