Heat Transfer Measurements in an Expansion Tube Using Infrared Thermography

This paper presents two-dimensional heat transfer results for the first time in an expansion tube, using infrared thermography at a Mars entry condition. Experiments were performed in the X2 expansion tube at The University of Queensland in a Martian (CO2/N-2) test gas on a wedge model. Infrared filtering from 3.5 to 4 mu m was performed in data acquisition to remove significant radiation from the shock layer. Thermal images of a preheated surface from the infrared camera were used together with measurements from a fast response infrared sensor to obtain heat flux maps at a hypervelocity condition with flight duplicated enthalpy. Experimental heat flux results have an uncertainty of less than 10% and agreed with laminar convective theoretical correlations to within 16%, making thermography suitable for heat transfer measurements in expansion tubes. This technique has potential for future applications in studying wall/near-wall viscous phenomena dependent on surface temperatures in expansion tubes.