Experimental study of heat transfer in a sphere levitating in a duct
A.H. Abed1, S.E. Shcheklein2
1Baghdad University of Technology, Baghdad, Iraq
2Ural Federal University named after the first President of Russia B.N. Yeltsin, Yekaterinburg, Russia
Keywords: heat transfer, heat-generating sphere, levitation, rotation, non-stationarity, boundary layer
Abstract
This article presents experimental results for determining the heat transfer intensity under aerodynamic suspension (free levitation) conditions for a spherical body in an air flow in a diffuser duct. Surface temperatures during heating and the sphere's rotational velocity were measured using contactless methods. It was established that over a wide range of airflow velocities, rotational motion of the sphere along two coordinates occurs, leading to a fundamental change in the hydrodynamics of the flow around it, manifested in the absence of stationary separation zones in both the front and rear sections. Heat transfer coefficient studies were performed using a non-stationary method at various initial sphere surface temperatures and airflow Reynolds numbers. For comparison, a study was conducted on a sphere fixed in the flow under the same conditions. It was found that the free aerodynamic suspension of the sphere allows for equalization of the surface temperature field and significantly intensifies heat transfer compared to a fixed sphere. Experimental heat transfer results show that cooling time decreases and the Nusselt number increases with increasing sphere rotation speed by 300-600%.
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