Transient thermal analysis of the coupled radiative and convective heat transfer in a porous filled tube exchanger at high temperatures

The transient thermal performance of coupled radiative and convective heat transfer in a circular tube exchanger filled with porous material subjected to constant wall temperature is investigated numerically. The porous material is considered as a homogeneous, absorbing, emitting and isotropic scattering medium. Monte Carlo method is used to solve the radiative heat transfer. The local thermal non-equilibrium model is employed to represent the energy transport within the porous material. The temporal temperature difference between the fluid and solid phases is analyzed to assess the availability of local thermal equilibrium model. The effects of different parameters are discussed, such as porosity, average particle diameter, inlet fluid velocity and the solid-phase thermal conductivity. The results indicate that the local thermal non-equilibrium mainly exists in the entrance region during the transient coupled heat transfer within porous material. Increasing the porosity, average particle diameter and inlet fluid velocity causes obvious temperature difference during the transient process. Besides, the solid-phase thermal conductivity has a considerable effect on the temporal temperature difference.