Approximation calculation of radiant heat transfer in a duct of rectangular cross section

Abstract

An approximate radiant heat-transfer calculation method of dealing with cylindrical systems of rectangular cross section is presented in the paper. Under given conditions, the two-dimensional theory may be applied. A system of gray walls is considered, filled with an absorbing medium having no reflectivity and no refractivity. The method of solution of the problem is based on integral equations. Calculation can be carried out in the following way : 1. 1. The system is divided into zones. 2. 2. For a duct of rectangular cross section, having four surface zones and two volume zones, direct interchange factors and areas are determined by (21) to (29). 3. 3. Determination of overall interchange areas and factors is carried out by using (30) to (33). 4. 4. Calculation of resulting heat fluxes or zone temperatures is carried out using (17) and (18). The method is illustrated by an example. The numerical part of the example is given in Table 3, whilst in Table 4 some experimental data are compared with initial conditions and results of the numerical example. The method can be used for solving problems on radiant heat transfer if various locations of the flame in the furnace chamber are to be taken into consideration. The method may also be useful in determining resulting heat flux distribution in a cross section of the furnace.