Mechanisms of Heat Transfer Augmentation around the Stagnation Point of an Impinging Air Jet Laden with Solid Particles. (Report 1. Evaluation Procedure of Heat Transfer Augmentation due to Unsteady Heat Conduction between Laden Particles and Heat Transfer Surface).

Abstract

In this study, the authors studied mechanisms of heat transfer augmentation around the stagnation point of an impinging air jet laden with solid particles. Primary attention was paid to the heat transfer augmentation around the stagnation point of gas-solid two-phase impinging jets due to unsteady heat conduction between the laden particles and heat transfer surface. The unsteady heat conduction to a solid particle was numerically studied and effects of thermal properties of both solid particles and the heat transfer surface were examined. The results clearly showed that the amount of heat conducted to a particle is influenced not only by the thermal properties of a particle but also by the ones of a heat transfer surface. Using the obtained results, the authors introduced an evaluation procedure which can separately assess the contribution of unsteady heat conduction. This procedure utilizes the change of unsteady heat conduction by the thermal properties of heat transfer surface material; the contribution of unsteady heat conduction is inversely evaluated by comparing the numerical results of unsteady heat conduction with the heat transfer augmentation measured for the different heat transfer surface materials.