Abstract
Buoyancy-driven airflow that included two isothermal inner plates established in a vented cavity is investigated numerically. The thermally optimum wall-to-wall spacing of the immersed channel, as well as its dependence with respect to the relevant governing parameters, are determined. Results are presented as a function of the aspect ratio b/H for a wide range of Rayleigh numbers RaH. A logarithmic correlation for the optimum (b/H)opt as a function of RaH is presented. In addition, since the outlined configuration might be subject to intense heating conditions, the influence of considering variable thermophysical properties is also included in the analysis. In fact, an appreciable influence of the variation of properties on (b/H)opt is also detected for a representative value of RaH = 109. Obtained results can be directly applied to the optimization of electronic equipment cooling, or even to thermal passive devices in buildings.
Highlights
From the pioneering experimental study of Elenbaas [1], configurations formed by vertical heated plates with fluid flows induced by buoyancy effects have been the topic of several studies (Incropera and De Witt [2], Bejan [3])
The determination of the thermally optimum spacing bopt that maximizes the heat transfer rate per unit area can achieve the thermal optimization of the system
Ra are graphically plate spacing varies, systematic results are obtained for the wide range of Rayleigh number presented inand
Summary
From the pioneering experimental study of Elenbaas [1], configurations formed by vertical heated plates with fluid flows induced by buoyancy effects have been the topic of several studies (Incropera and De Witt [2], Bejan [3]). The natural convection is a mode of heat transfer that presents undoubted advantages, under given circumstances. A relevant review of benchmark solutions for natural convection flows in vertical channels was presented recently by Desrayaud et al [4]. The optimization problem for the described issue is represented by the electronic equipment cooling. In this case, one of the most important objectives consists of dissipating the heat generated in the devices to avoid overheating. The determination of the thermally optimum spacing bopt (between the plates or walls forming the vertical channel) that maximizes the heat transfer rate per unit area can achieve the thermal optimization of the system. A given optimization function can be obtained from the appropriate correlations for calculating the heat transfer rate. The optimum was reached for a modified Rayleigh number Ra*
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