Abstract
The airflow in the exhaust pipe of an automobile engine fluctuates periodically in terms of flow velocity and gas temperature, and understanding the complex flow and heat transfer characteristics is extremely important for improving the performance of exhaust systems. In this study, using a horizontal rectangular pipe with a rectangular cross section, we experimentally obtained the time-averaged temperature in the cross section measured by thermocouples and the wall temperature by thermography on the outer wall of the pipe under the pulsation conditions assumed in the actual system, and investigated the effects on the heat transfer characteristics. The influence of flow characteristics on heat transfer characteristics was also investigated by using PIV. The results showed that the heat transfer coefficient peaked at a pulsation frequency of 25 Hz. At higher frequencies, the decrease in velocity amplitude was considered to be responsible for the decrease in heat transfer coefficient. At lower frequencies, the decrease in turbulent energy in the area close to the inner wall was considered to be the cause.
