Effect of pulsation frequency of airflow in a horizontal rectangular tube on wall heat transfer

Abstract

This study is directed toward the application of temperature fields due to pulsating flows in automobile exhaust pipes for active control. The temperature fields in multiple cross sections of pulsating and steady flows of high temperature air with an average Reynolds number of about 60,000 flowing in a horizontal straight tube with a rectangular cross section were measured with thermocouples. Measurements were made under pulsating conditions of 15Hz, 30Hz, 45Hz and 90Hz to investigate the change in heat transfer characteristics with pulsating frequency. As a result, it was found that the heat transfer was suppressed by the pulsating flow. At a pulsation frequency of 30 Hz, which is close to the resonant frequency of the piping, the heat transfer was suppressed more than in other pulsation conditions. In this condition, a strong reverse flow occurred. The strong reverse flow made it difficult for heat to escape, and heat transfer was suppressed.