The Experimental Investigation on the Transpiration Cooling : (2nd Report, Coolling Effectiveness and Heat Transfer Performance of Gaseous Coolant)

Abstract

The heat transfer coefficient and the cooling efficiency with transpiration of gaseous coolant were decided experimentally. The conditions selected for the experiments were as follows : Velocity of free stream is 5∼25 m/sec Temperature of free stream is 100∼600°C Coolant flow ratio is 0.5∼5% From these investigations the following results were obtained. (1) The cooling efficiency is proportional to the cooling flow ratio and the proportionality constant increases with Reynolds number of free stream. (2) The heat transfer coefficient invreases with the coolant flow ratio and then begins to decrease. The coolant flow ratio for the maximum value of heat transfer coefficient decreases with an increasing Reynolds number of free stream. (3) The ratio of Nusselt number with and without transpiration of air remains at about unity or slightly larger than unity.