LOCAL CONVECTIVE HEAT TRANSFER TO IMPINGING CIRCULAR JETS WITH DIELECTRIC LIQUIDS

摘要

Experimental study was performed to investigate local heat transfer characteristics from a simulated microelectronic chip of 5mm x 5mm with impinging circular jets, using dielectric liquid as working fluid. Heat transfer coefficients of stagnation point and lateral location were determined systematically, and all the experimental data were correlated. The results revealed that stagnation heat transfer rate enhanced with increasing jet Reynolds number and decreasing nozzle diameter and nozzle-to-plate spacings, and that submerged jets was rather an efficient means to obtain higher heat transfer rate than free-surface jets at the same conditions, and that a bell distribution was gained for radial local heat transfer coefficient. The latter decreases with elevating radial distance, and then remains a constant approximately due to the occurrence of hydraulic jump at r/d=5.6. This is consistent with the theoretical result. Single-phase convective heat transfer is still remained while the surface temperature of the heater is beyond saturation temperature of working fluids. The results of the correlation Nu_0～Re showed that the coefficients decreased with increasing radial distance, yet the power of Reynolds number enhanced. The power of Reynolds number characterized liquid flow because the distribution of radial local heat transfer coefficient was controlled by pressure gradient along the impinging plate.