Abstract
In this paper the interaction of thermal radiation and laminar forced convection in the thermal entrance region of noncircular ducts is numerically investigated. In particular, because of their complex geometry, the paper investigates in detail the combined modes of heat transfer in right triangular and semicircular ducts. The velocity in these geometries is considered fully developed and the temperature of an absorbing-emitting gas is developing in an isothermal duct with nonblack walls. The method of moments is used to describe the radiation contribution that circumvents the partial intergro-differential equation typical of this kind of problem. Also, the methodology using the method of lines (MOL) involving differential and difference formulations and coarse grids is applied to these ducts of noncircular cross section. The results based on 36 lines or less are computed numerically using a Runge-Kutta subroutine. They are presented in terms of axial bulk temperature and mean Nusselt number and are plotted as a function of the optical thickness, wall emissivity, and radiation-conduction parameter. The results compare very well with those for pure convection available in the literature. In addition, it is observed that radiation influences the thermal development of noncircular ducts in a complicated way.
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