Effects of Size of Simulated Microelectronic Chips on Boiling and Critical Heat Flux

Microelectronic chips were simulated with thin foil heaters supplied with d-c power and arranged in two vertical configurations: flush mounted on a circuit board substrate or protruding from the substrate about 1 mm. Heat transfer characteristics (midpoint) were obtained with varying height (1 mm to 80 mm) and width (2.5 mm to 70 mm) in R-113. Two types of incipient boiling temperature overshoot were observed with saturated boiling. The inception of boiling depended greatly on the location of the active boiling sites on the heater. For arrays, the inception of boiling for the top heater took place at lower superheat than for the bottom heater. Heater size had no effect on established boiling, in contrast to results reported previously in the literature. The critical heat flux for wide heaters increased with decreasing heater height, as expected. The critical heat flux also increased with decreasing width. Correlations are presented that describe these effects.