Investigation of Radiation and Conjugate Heat Transfers for Vehicle Underbody

A computational study was conducted in order to characterize the heat transfers in a sedan vehicle underbody and the exhaust system. A steady-state analysis with consideration for both the radiation and conjugate heat transfers 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. All three mechanisms of heat transfer, i.e., convection, conduction, and radiation, were included in the analysis. The convective heat transfer due to turbulent fluid motion was modeled with the assumption of constant turbulent Prandtl number; and heat conduction was solved directly for both fluid and solid.

The analysis was carried out at a given set of vehicle and ambient conditions, such as ambient temperature, exhaust specific heat, external emissivity, pipe surface area, the velocity and temperature of the internal exhaust gases which depend on the engine operation conditions and the velocity and temperature of the external airflows which depend on vehicle operations. These variables were independently studied to determine their contribution to changes in exhaust gas temperature and system heat flux.