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INFLUENCE OF THE FLOW TURBULENCE ON THE HEAT CONVECTION ON A SPHERE

DOI: 10.1615/ICHMT.2014.IntSympConvHeatMassTransf.1090
pages 1451-1459

Leon Boguslawski
Poznan University of Technology, Faculty of Machines and Transport Chair of Thermal Engineering, 60-965 Poznan, Poland

Аннотация

The paper presents the results of experimental investigations of heat transfer on spheres in a turbulent flow. Experimental data indicate that the turbulence of the external flow intensifies the process of heat transfer. Measurements of the average value of the heat transfer coefficient on a sphere render results that are in good agreement with literature data for low values of inflow turbulence intensity. It is observed that an increase in the inflow turbulence level of approx. 22% causes an increase in the heat transfer intensity of approx. 30%. The paper also presents the influence of the turbulence of the external flow on the distribution of the local heat transfer coefficients. The analysis of the experimental data suggests that the external flow turbulence influences the structure of the process of local heat transfer on a sphere. Up to the angle of approx. 60°, the structure of turbulent fluctuations on the sphere surface is under the control of the structure of the external inflow. For wider angles, the external influence disappears and the structure of the turbulent fluctuations is created mainly by local sources of turbulence. The increase in the inflow turbulence can intensify the heat transfer even if the average velocity is constant because the heat transfer process gets more intense. For the highest value of flow turbulence level, however, the increment of heat convection stabilizes.

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