A theoretical and experimental approach to heat transfer from high temperature gas flowing inside nonhomogeneous rectangular pipes

The purpose of the present paper is to develop a mathematical model for predicting thermal field and heat transfer inside short length/height ratio, rectangular and nonhomogeneous material pipe connecting a combustion chamber with outdoors, while the gas combustion temperatures are in the range of 2 000 to 3 000 K and the pipe is made of heat-resistant material. The used approach is based on a finite difference simulation and makes certain idealizations and approximations in order to get to an engineering workable and at the same time adequate, solution. Main assumptions are an equivalent temperature cavity to describe radiant heat transfer due to both the combustion chamber luminous flame and outdoors.

The proposed model shows a very good agreement with experimental results coming from an experimental set-up used for materials testing, that is embodied in a refractory rectangular pipe, at high temperature.