Thermal radiation and laminar forced convection in the entrace region of a pipe with axial conduction and radiation

Abstract

Combined forced convection and thermal radiation in the thermal entrance region of a circular pipe with axial heat conduction and thermal radiation are numerically studied in this article. The fluid is treated as a gray, absorbing and emitting medium with a fully developed velocity entering an isothermal semi-infinite long pipe. The method of moments is applied to approximately model the radiative heat transport process. The governing equations are solved by applying the SIMPLE algorithm. The effects of the Peclet number and its interaction with the conduction-radiation parameter and optical thickness on heat transfer behavior in the thermal entrance region are also investigated. The results obtained indicate that radiation plays more important role at a low Peclet number than at a high Peclet number and that axial radition is negligible when the Peclet number N>20. The numerical results for limited cases of no axial heat conduction and radiation are also compared with the available data published in open literature. In all cases, good agreement with these studies was obtained.