AN IMPROVED DISCRETE TRANSFER METHOD FOR 3-D SURFACE RADIATION CALCULATION

Abstract

Surface radiation heat transfer may become a dominant mode of heat transfer in many engineering applications, and its accurate and efficient modeling is the key to the efficient design of the involved systems. In the study, an improved discrete transfer method (DTM) is developed to meet practical needs for surface radiation modeling. A direct application of the DTM to modeling surface radiative heat transfer usually leads to a large error, due to the strong ray effects. In order to eliminate the ray effects, a total of nine discrete directions over a control angle instead of a single discrete direction as used in the traditional DTM is selected, and the incident radiative intensity over this control angle is then replaced by a weighted-averaged intensity from these nine discrete directions. This approach provides a more accurate value on the mean radiative intensity over a control angle, while it does not increase the total number of radiative intensity to be solved at a surface element. Compared to the modified DTM we developed previously, the present approach is much simpler in terms of numerical treatment. In order to examine the accuracy of the present method, two 3-D benchmark problems are selected and investigated. With a reasonably fine angular discretization, the present solutions are found to match the exact solutions and they are much more accurate than the results from the traditional DTM.