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Experimental study of the convective heat transfer coefficient in a packed bed at low Reynolds numbers

Messai Souad (Institut Supérieur des Sciences Appliquées et de Technologie de Gabès, Tunisie)
El Ganaoui Mohammed (Institut Universitaire de Technologie de Longwy, France)
Sghaier Jalila (Laboratoire d’Energétique et des Transferts Thermiques et Massiques, Tunis, Tunisie)
Belghith Ali (Laboratoire d’Energétique et des Transferts Thermiques et Massiques, Tunis, Tunisie)

An experimental study to evaluate the convective heat transfer coefficient in a cylindrical packed bed of spherical porous alumina particles is investigated. The task consists in proposing a semi-empirical model to avoid excessive instrumentation and time consumption. The measurement of the bed temperature associated to a simple energy balances led to calculate the gas to particle heat transfer coefficient using a logarithmic mean temperature difference method. These experiments were performed at atmospheric pressure. The operating fluid is humid air. The gas velocity and temperature ranged from 1.7-3 m/s and 120-158°C, respectively. The data obtained was compared with the correlations reported in the literature. It is shown that the proposed model is in reasonable agreement with the correlation of Ranz and Marshall. Despite, many researches on experimental investigations of heat transfer coefficient in packed beds at low and average temperature are proposed, few studies presented calculation of convective heat transfer coefficient at high temperature (above 120°C). A possible application of the proposed model is drying and combustion.

Keywords: heat transfer coefficient, energy balance, packed bed, temperature measurements