| Abstract: | The influence of thermal radiation on laminar forced convection of a gray gas in a pipe flow is studied semi-analytically. The gas is considered as an absorbing-emitting medium and the thin gas model approximation is used to describe the radiative heat flux in the energy equation. Invoking the method of lines (MOL), the nonlinear boundary value problem is reduced to an initial value problem which is eventually solved by a standard Runge-Kutta integration scheme. Numerical results are presented graphically for a selected group of thermal parameters encompassing the thin gas behavior. Additionally, it is found that limiting cases namely: laminar plug flow and laminar parabolic flow, both in the absence of radiation define an envelope for the curves of bulk temperature and total Nusselt number describing the combined thermal process for a thin gas in laminar motion. In general, the comparisons reveal that these asymptotic solutions are valid when the entrance-to-wall temperature ratio is less than 2. |
