Abstract
This study aims to numerically investigate the radiation heat transfer in a complex, 3-D biomass pyrolysis reactor which is consisted of two pyrolysis chambers and a heat recuperator. The medium assumes to be gray, absorbs, emits, and Mie-anisotropically scatters the radiation energy. The finite volume method (FVM) is applied to solve the radiation transfer equation (RTE) using the step scheme. To treat the complex geometry, the blocked-off-region procedure is employed. Mie equations (ME) are applied to evaluate the scattering phase function and analyze the angular distribution of the anisotropically scattered radiation by particles. In this study, three different states are considered to test the anisotropic scattering impacts on the temperature and radiation heat flux distribution. These states are as: (i) Isotropic scattering, (ii) forward and backward scattering and (iii) scattering with solid particles of different coals and fly ash. The outcomes demonstrate that the radiation heat flux enhances by an increment of the albedo and absorption coefficients for the coals and fly ash, unlike the isotropic case and the forward and backward scattering functions. Moreover, the particle size parameter does not have an important influence on the radiation heat flux, when the medium is thin optical. Its effect is more noticeable for higher extinction coefficients.
Highlights
For a vast range of engineering applications, radiation is a substantial method of heat transfer.Especially, in high temperature equipment like furnaces, boilers, gas turbine combustors, and nuclear reactors, where the combustion generating luminous flames includes combustion gases and other particles
The temperature of all the walls was evaluated equal to 300 K with an emissivity equal to = 0.8, except the wall at y = 0 and for 0.75 < x < 1.05 m, where the temperature was assumed 1000 K with a blackbody surface
The two pyrolysis chambers are considered as black and at a uniform temperature 500 K. This choice is made based on experimental measurements
Summary
For a vast range of engineering applications, radiation is a substantial method of heat transfer.Especially, in high temperature equipment like furnaces, boilers, gas turbine combustors, and nuclear reactors, where the combustion generating luminous flames includes combustion gases and other particles. For a vast range of engineering applications, radiation is a substantial method of heat transfer. Where the scattering is mostly anisotropic, the particles emit, absorb and scatter radiant energy. The necessity for analysis of radiation heat transfer leads to an increase demand for developing well-designed radiation models, applicable to arbitrary shaped multi-dimensional. Energies 2019, 12, 3986 geometries and capable of treating anisotropic characteristics in participating media. Many researchers have tried to calculate the radiation transfer equation (RTE) in multidimensional complicated geometries. The first description of the discrete transfer method (DTM) is presented by Lockwood and Shah [1] and applied later to complex geometries by the cell-blocking process according to Cartesian coordinates [2], and nonorthogonal grid systems [3]. Chai et al [4] used the DOM with the blocked-off-region procedure
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