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Show 6. Results and Discussion For the present work, computations were made for run no. R930716 of the CAGCT furnace at conditions of full firing rate of natural gas fuel, to all three side wall burners, with full sink exposure. Several parameters in computations have been investigated. Details of the effect of each parameter are discussed in the following subsection. 6.1 Effect of radiative absorption coefficient The first specific objective of the computations is to investigate the optimum value of the radiative absorption coefficient by comparing the predictions of total sink heat flux, local sink heat flux and local refractory temperatures with the measurements. The computation was carried out by using 45xllx30 grid and keeping mass mb and momentum flux Gb on 3x3 control surface elements of the burner exit plane the same as those on the real burner inlet, mexp. and G exp. ' Figure 6 shows the computed results for heat flux distribution, total heat heat and volume average gas temperature at three levels of radiative K = 0.2,0.3 and 0.4. The measurements for heat flux distribution and the total heat flux are also plotted on the same graph. It is shown that the heat flux profile of the computed results is pick up very well for all three values of K. The values of the local heat flux on the panels in row number 4 (z = 2.5) are very close to the experimental values. Under-predictions of the heat flux are in evidence for panels in row 3 (z = 1.5). On panels row 3, the under-predictions are found at x = 0.75 to 1.25m; the other panels in this row show good predictions. However, for the first row, the computed heat fluxes are slightly over predicted. From this comparison, it can be said that the predictions show good agreement with experiment in the far-field, along row number 4 or x > 3m. Over-prediction in row number 1 is expected because of the simplified combustion model where the gases enters the combustion chamber at adiabatic flame temperature. Under prediction in the region z = 0.75 to 1.5m and x = 0.75 to 2.5m, on the other hand, is attributable to the neglect of the convection heat transfer. In this region, the discrepancies between .the computed results and the experiments are less than 15%. The presence of strong convection is supported by the flow recirculation seen in Fig. 1Ic at x = 0.75m. Higher value of radiative absorption coefficient K gives higher predictions of the heat flux. The difference of the predictions among three levels of K is not large. The realistic range of values of K can be estimated from the emissivity of the combustion gas products. At 10 |