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Home Archives Officers Future meetings American Society of Thermal and Fluids Engineering

ISSN Online: 2379-1748

ISBN Print: 978-1-56700-472-4 (Flash Drive)

ISBN Online: 978-1-56700-471-7

3rd Thermal and Fluids Engineering Conference (TFEC)
March, 4–7, 2018, Fort Lauderdale, FL, USA

A NUMERICAL STUDY OF NATURAL CONVECTIVE HEAT TRANSFER FROM AN UPWARD FACING CIRCULAR HEATED HORIZONTAL ISOTHERMAL ELEMENT WITH A NON-FLAT SURFACE

Get access pages 97-111
DOI: 10.1615/TFEC2018.cfd.021539

Abstract

The use of a non-flat surface to increase the natural convective heat transfer rate from an isothermal circular horizontal element has been numerically investigated. The case where the height of the element surface rises linearly from its outer edge to a maximum at the center of the element, the case where the height of the surface increases in two linear steps from its outer edge to its center, and the case of a curved surface have been considered. Conditions under which laminar flow, transitional flow, and turbulent flow exist have been considered. The flow was assumed to be axisymmetric and steady and the Boussinesq approach was adopted. The standard k-epsilon turbulence model was used. The mean heat transfer rate from the element surface was expressed in terms of a Nusselt number based on the diameter of the element. For each of the three surface shapes considered this Nusselt number is a function of the Rayleigh number, of the dimensionless height of the surface, and of the Prandtl number. Results were only obtained for a Prandtl number of 0.7, i.e., effectively the value for air at standard ambient conditions. A range of the other governing parameter values has been considered. The results indicate that the use of non-flat element surfaces of the types considered can produce an enhancement of the heat transfer rate compared to that from a plane horizontal surface but the results show that the heat transfer enhancement is relatively small under many of the conditions considered.
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