For a boiling process such as shown in Figure 1.5c, the ambient temperature T_∞ in Newton’s law of cooling is replaced by the saturation temperature of the fluid T_sat. Consider a situation where the heat flux from the hot plate is q" = 20 X 10⁵ W/m². If the fluid is water at atmospheric pressure and the convection heat transfer coefficient is h_w = 20 X 10³ W/m² · K, determine the upper surface temperature of the plate, T_s,w. In an effort to minimize the surface temperature, a technician proposes replacing the water with a dielectric fluid whose saturation temperature is T_sat,d  = 52°C. If the heat transfer coefficient associated with the dielectric fluid is h_d = 3 X 10³ W/m² · K, will the technician’s plan work?

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(a) (c) Forced flow Vapor- bubbles Air q" -Water Hot plate - Hot components- on printed circuit boards (b) (d) Buoyancy-driven flow Cold water Air Moist air - Water droplets