OCR Text |
Show If all surfaces in the enclosure are visited and rays traced forward and backward, then the incident radiation for each surface is obtained. Since the backward ray traces require a previous iteration value of incident radiation at surface Q, the calculations must be repeated for all surfaces. Iterations are, therefore, required until incident radiation for all the surfaces converges to within some preset convergence criteria. The wall heat transfer is computed with the incident radiative flux, a , obtained from the radiation module according to the expression: H\<T " V • V < " O + ^ R ^ - 0 <21> \ where Ax 1 ^ • * \ + *A; (22) Eq. 21 is solved with the Newton-Raphson technique for wall temperature, T . Wall temperatures and internal control volume temperatures are then provided to the radiation module for the next iteration. The B&W developed computer program, NOXMO, was used for the NO pollutant analysis. It extends the capabilities of COMO to predict NO emissions from combustion systems. The model is presented in Reference 5. To summarize, NOXMO accounts for thermal NO, fuel NO and NO-char reduction mechanisms as follows: -12- |