Radiative heat transfer from a plasma in tube flow

Abstract

Schmidt and Leppert (1970) have reported experimental and analytical heat-transfer data for partially ionized argon flowing in a circular tube. The finite-difference model used, which was based on the then best available information, considerably underpredicted the total heat flux to the wall in the first few tube diameters. The present study has developed a new finite-difference program, based on the Spalding-Patankar GEN program, which predicts local heat transfer for a partially ionized argon plasma flowing in a cooled, circular tube. The equilibrium radiation model incorporated in the program has been refined to include the effects of the geometry of the radiating flow field. Experiments were conducted, using a newly developed annular radiometer, which showed the total radiation incident on the walls of the tube to be much higher than predicted. It is concluded that the discrepancy earlier reported was due to a 50 per cent underprediction of the radiative heat transfer. Non-equilibrium radiation appears to be the cause of this behavior.