Natural Convection Immersion Cooling of an Array of Vertically Oriented HeatedProtrusions in an Enclosure Filled with a Dielectric Liquid: Effects of Enclosure Width, Prandtl Number and Component Orientation

摘要

The natural convection heat transfer characteristics of a 3x3 array of verticallyoriented heated protrusions, immersed in a dielectric liquid, were investigated. Aluminum blocks, 24mm x 8mm x 6mm, were used to simulate 20 pin dual in-line packages. Surface temperature measurements of the components were made by imbedding copper-constantan thermocouples below the surface of each component face. A constant heat flux was provided to each component using an Inconel foil heating element. Power supplied to each component varied from 0.115W to 2.90W. The aluminum blocks were mounted on a plexiglass substrate to form a 3x3 array of simulated electronic components. The circuit board containing the components was placed in a rectangular, plexiglass enclosure with inner dimensions: L = 203.2mm H = 152.0mm W = 82.6mm, and a wall thickness of 25.4mm. The upper boundary was maintained at 10 C, while all other exterior surfaces were insulated. The chamber width, measured from the surface of the circuit board to the opposite, inner wall of the enclosure, was varied from 42mm to 7mm by inserting plexiglass spacers into the enclosure. Two dielectric liquids, FC-75 and FC-43, were used as working fluids. Non dimensional data from this study was combined with the data obtained for a horizontal component orientation, to develop an empirical correlation which predicts the Nusselt number as a function of Rayleigh number, Prandtl number, component orientation and chamber width. This correlation was found to be accurate to within 11% of the original curve fit data.