Mass Transfer Cooling on a Porous Flat Plate in Carbon-Dioxide and Air Streams

Abstract

Heat transfer results are reported for a transpiration cooled porous flat plate placed in a stream of air and in a stream of CO2 . The tests were performed at a Mach number of 1.96 over a range of effective length Reynolds number, from 5 million to 9.1 million, when CO2 was used as the free stream gas. A Mach number of 2.53 for an effective length Reynolds number range of 5.3 million to 8.3 million was characteristic when the free stream gas was air. The heat transfer data were normalized and presented as the ratio of the Stanton number to the no-blowing Stanton value (St/St0 ) as a function of the dimensionless transpiration rate F/St0 . The recovery factor data were also normalized and presented as the ratio of r/r0 as a function of the transpiration rate F. The results for both the air and the CO2 free stream flows showed a reduction in heat transfer with increasing transpiration rate, using air and CO2 as the injectant gases. The measured recovery factor and the normalized recovery factor also decreased with increasing transpiration for the reported gas combinations. It was found that Rubesin’s air theory adequately predicts all of the heat transfer results including those obtained in CO2 atmospheres within the reported Mach number range. Also, the empirical theories which predict recovery factor results for air free streams can be used for air or CO2 injection into a CO2 free stream gas.