The paper reports on the prediction of turbulent heat transfer in flows between parallel plates with wall transpiration. The elliptic blending second moment closure for turbulent stresses and the GGDH model for turbulent heat fluxes are employed to predict the turbulent flow and heat transfer. The numerical results by the adopted models are directly compared to the DNS data and the measurements to assess the performance of the model predictions. The predictions show correctly the effect of deceleration and acceleration of the flow caused by the transpiration, and the anisotropy of the turbulence structure is augmented towards downstream by the fluid injection. The turbulence structure and heat transfer characteristics of transpired flows are well captured by the present turbulence and heat flux models.

For material recovery of black carbon and pyrolysis oil, pyrolysis is considered as an alternative to combustion-based technologies for treatment of waste tire. This study investigated the heat transfer optimization in a pyrolysis reactor for waste tire chips with a capacity of 24 t/d. The reactor was required to have a larger heat transfer rate from hot gas to tire chips in the early stage of pyrolysis, whereas the rate in the later stage should be lower. This was to prevent thermal cracking of heavy compounds in the pyrolysis vapor and to improve the quality of black carbon. CFD was applied to analyze the flow and heat transfer in the complex geometry of the reactor for a total of nine design cases. It was found that modifications to control the distribution of gas flow rate along the reactor are more effective for the present reactor than adjusting the measures for heat transfer enhancement (such as fins). The ideal design improvement was to divide the reactor into two gas sections for a separate control of the flow rate, and to remove the fins of which its alignment perpendicular to the flow inhibits the hot gas from approaching the tube of tire chips.