The effect of internal particle heat conduction on heat transfer analysis of turbulent gas–particle flow in a dilute state

Abstract

In many cases the conduction mechanism inside a particle can not be ignored (large particles, low thermal conductivity and high porosity) during turbulent gas–particle flows. However, the accurate solution might be difficult to apply. Therefore, we first develop here the ability to conduct accurate solution and then we define the criterion for which the internal conductivity might be ignored. A combination between commercial C.F.D. code and user defined programs was developed to predict numerically the gas–particle velocity and temperature profiles. The selected criterion (defined at the outlet of the pipe’s cross-section), referred to the relation between the computational desirable average temperature difference \((T_{{\rm p}_{_{\rm wall}}} - {{T_{\rm p}}_{_{\rm center}}})_{_{_{\rm AVERAGE}}}\) without ignoring internal heat conductivity and the average particles temperature \({T_{\rm p}}_{_{\rm AVERAGE}}\) by ignoring internal heat conductivity, determines whether to consider the heat conduction mechanism in numerical simulations or to ignore it. It was found that the average particles temperature for Tp = f(r) is lower than the case when Tp = constant. Also, it was found that the non-dimensional temperature difference criterion is a continuous function of [Bi × (dp/D)] for a specific geometry, various pipe and particle diameters, various particles’ thermal conductivities, constant heat flux and Re number. The numerical code enables to extend the classical criterion for Bi number of solids to various gas–particle systems and different operational conditions.