Investigation of fluid-solid conjugate heat transfers for a sedan exhaust system

A simple model was constructed in order to characterize the fluid-solid conjugate heat transfers in a sedan exhaust system. It can compute the temperatures of airflows and exhaust surface from the exhaust temperature and mass flux of the exhaust gas by modeling the fluid-solid conjugate heat transfers of the internal pipe flows, exhaust pipes and the external airflows. The analysis was undertaken using the High Reynolds formulation of the k-epsilon turbulence model with standard wall function and the DO model for the radiation heat transfer. The results show the internal pipe flows temperature reduces gradually to about 310°C at the exhaust ports but the temperature of external airflows and exhaust pipe surface increase to 140°C and 300°C respectively, and the results also show they are reasonable for the simplified model and boundaries. The quantitative results of steady-state and unsteady-state are compared and show the results are not any noticeable differences, and the results also show the quasi-steady method is feasible for analyzing the heat transfer at the same engine operating cycle.