The effect of microscopic and global radiative heat exchange on the field predictions of compartment fires

This paper reports on some further results of the CFD simulations of large- scale compartment fires previously reported in Wen et al. (Proceedings of t he Combustion Institute, vol. 27, 1998) and Well and Huang (Fire Safety J 2 000;34(1)). It focuses on the use of the laminar flamelet approach and high lights the effect of microscopic radiation on the field predictions of temp erature and species concentrations in compartment fires. The flamelet calcu lations with and without microscopic radiation are performed using RUN-1DL (Rogg. RUN-1DL Manual, 1099). Radiative properties in the flamelet are calc ulated by a modified exponential wide band model. Global radiation is coupl ed with the field calculation through the discrete transfer radiation metho d (Shah. Ph.D. thesis, Imperial College of Science and Technology: 1979) an d Hubbard and Tien's (ASME J Heat Transfer. 1978;100:235-9) mean emission a nd absorption coefficient concept. The soot model of Leung et al. (Combust Flame 1991;87;289-305) is used for soot predictions. Improved agreement wit h experimental data on temperature distributions has been achieved by inclu ding the microscopic radiation in the flamelet calculation. Microscopic rad iation is also found to have significant effect on the predictions of soot and OH radical but its effect on the predictions of CO2, CO and H2O are fou nd to be marginal. The present study recommends that radiative heat exchang e at microscopic level (within the laminar flamelet) should be included whe n using the laminar flamelet approach to compute turbulent reacting flows. (C) 2001 Elsevier Science Ltd. All rights reserved.