Microelectronic circuits were simulated with thin foil heaters supplied with d-c power. The heaters were arranged in two configurations: flush mounted on a circuit board substrate or protruding from the substrate about 1 mm. Heat transfer coefficients (midpoint) were obtained with two heater heights (5 mm, 10 mm) and varying width (2 mm ∼ 70 mm), in water and R-113. The height effect for single flush heaters agrees qualitatively with conventional theory; however, even the widest heaters have coefficients higher than predicted due to leading edge effects. The heat transfer coefficient increases with decreasing width, with the coefficient for 2 mm being about 150 percent above that for 20 mm ∼ 70 mm. This is attributed to three-dimensional boundary layer effects. The protruding heaters have a coefficient about 15 percent higher. Data were obtained for in-line and staggered arrays of flush heaters with varying distance between heaters. Coefficients for the upper heaters are below those for lower heaters, with the differences diminishing as the vertical or horizontal spacing increases. For the protruding heaters, the upper heaters have higher coefficients than the lower heaters.

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