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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

PREDICTION AND CORRECTION OF SIDEWALL CONDUCTANCE FOR NATURAL CONVECTION IN HORIZONTAL ENCLOSURES

Get access (open in a dialog) DOI: 10.1615/IHTC16.cov.021359
pages 2731-2740

Resumo

Turbulent natural convection in horizontal enclosures, where the temperature gradient is vertical, occurs in numerous applications. Sidewall conductance loss can significantly alter the Nusselt number (Nu) predictions. Although it is ideal to use a sidewall material with very low thermal conductivity, some situations (such as visualization of flow patterns within the enclosure) demand the use of materials with slightly higher thermal conductivity. In the present study, experiments are designed and performed with sidewall materials of two different thermal conductivities and three decades of Rayleigh numbers (Ra ~ 106 − 109) to assess the effect of sidewall conductance on the Nu-Ra relation. Input power measurements, corrected for various other losses, show a visible difference indicating the effect of sidewall conductance. A fin model is proposed to estimate the steeper gradient, higher than a typically evaluated empty cell gradient, in the sidewall material at the hot end. The fin model predictions are found to be fairly accurate when compared with the experiments. A new correlation is proposed for Nusselt number in terms of Rayleigh number for an ideal zero thermal conductivity sidewall case by linearly extrapolating the data available for two different thermal conductivities.