Analysis of transient radiative heat transfer using high bounded scheme of the FTn finite volume method

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.In this work, the transient behavior of the absorbing, emitting, and isotropically scattering medium in radiative equilibrium is examined, using the FTn Finite Volume Method (FTnFVM), in terms of temporal and spatial evolutions of the incident radiation, radiative heat flux, and temperature of the medium. Commonly used convection schemes in computational fluid dynamics (CFD) such as STEP and CLAM are introduced for spatial discetization of the transient radiative transfer equation (TRTE). Also a non-uniform (FTn) angular scheme is used to capture the physics of the radiative wave propagation. The present approach is then validated by comparing with published data and applied to problems of three-dimensional isotropically participating media. It is shown that the FTn FVM reduces largely the ray effects. Also, the false scattering is largely remedied using the CLAM scheme is applied for the angular discretization. In all computations, the CLAM scheme produces more accurate results (with coarse grid) than the step scheme. Using the same (relatively coarse) spatial grid, the CLAM scheme captures the steep gradients and penetration depths more accurately than the step scheme. Then, effects of the scattering albedo and the optical thickness on the incident radiation distributions are presented and discussed.cf201

Modelling and experimental results of a biomass pyrolysis pilot plant

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Fire Dynamics Simulator (FDS) and global modelling are used to solve numerically pyrolysis, combustion and heat recuperation in a pilot plant of biomass pyrolysis using pyrolysis products as fuel. Obtained results are validated with experimental measurements. In the case of FDS modelling three different treatments of radiation are considered: without radiation, with gray gas radiation and with non gray gas radiation. The results of numerical simulations are compared with the global model results and with the experimental results. It was shown that the FDS results are in good qualitative and quantitative agreement with the experimental results. The global model gives qualitative results in agreement with experimental results with less CPU time compared with FDS results. Whereas FDS results are more accurate than those of the global model. At the end of the process FDS results are better than global model results this is due to the fact that global model doesn’t take into account the thermal inertia of the pilot plant. The global model is used to study the racing reaction in the pilot plant and to study the case with and without catalyser. FDS is used to predict CO and CO2 emissions. The effect of the non gray gas behaviour is emphasised and demonstrated to affect pollutant emissions.cf201