Convective-radiative heat transfer in a square duct with a centered circular core

Abstract

Combined laminar forced convection and radiation heat transfer have been numerically investigated for a gray, absorbing, emitting, nonscattering gas in the entrance region of a square duct with a centered, circular core. The thermal boundary condition imposed on the square duct and the core is a uniform temperature, both axially and peripherally. The method of moments is applied to considered the radiation contribution. The momentum equation, the three-dimensional energy equation, and the two-dimensional irradiaton equation are discretized and numerically solved by the control-volume-based finete-difference method in the boundary-fitted coordinate system. This numerical scheme is found to be simple, accurate, and efficient. The effects of four major parameters influencing combined convective and radiative heat transfer, namely, the geometry parameter, α ∗ , as well as radiation-conduction, N, optical thickness, τ b , and wall emissivity, ϵ w , are discussed in detail. The results for the total Nusselt number variations indicate that heat transfer is enhanced by thermal radiation. The predicted results for pure convective heat transfer are in good agreement with the available data published in the open literature.