Buoyancy Induced Convection in a Non-Uniformly Heated Array of Cubical Elements on a Vertical Channel Wall

摘要

Experiments have been performed to investigate naturally-induced convective heat transfer from an array of cubical elements that are deployed in an in line array on one wall of a vertical, open-ended parallel-planes channel. The application is in passive cooling of high density electronics, in which components, located in arrays of vertically arranged printed circuit board, are part of an asymmetrically heated channel, with one wall having large hydrodynamic roughness. An examination of the convective heat transfer from a single element in the family using purely local descriptors shows that the heat transfer is driven primarily by globally induced channel flow, rather than by local buoyancy mechanisms, when the channel walls are closely spaced and there is good fluid mixing at any streamwise location. It is preferable to describe the situation as one of ''buoyancy induced forced convection.'' As long as the local ratio Gr/Re sup 2 is less than about 0.3, for the cube array, local buoyancy effects can be neglected, and the hydrodynamics are indistinguishable from pressure-driven forced convection. This is confirmed by a comparison of local heat transfer coefficient measured in both buoyancy induced and forced channel flows. A method is derived by which the channel Reynolds number may be predicted even for cases of streamwise non-uniform heat dissipation in the array using experimental measurements of array drag coefficients. With this flow prediction capability, and with a data base that includes adiabatic heat transfer coefficients, and thermal wake decay functions, it is possible to implement an analytically exact linear superposition method to predict array element temperatures in a non-uniformly heated array. (ERA citation 11:038626)