Abstract To predict the performance of turbine materials at engine conditions, experiments are performed at lower temperature laboratory conditions. To ensure the results accurately predict the nondimensionalized surface temperature, the Biot number must be matched, requiring the ratio of the thermal conductivity of the material to that of air is matched. With alloys such as Inconel, it is sometimes assumed that the Biot number is matched since Inconel's thermal conductivity variation scales similarly to that of air. However, the thermal conductivity ratio does not scale perfectly sosome Biot number error exists, with the problem exacerbated at lower temperatures. To date, there has been no quantification of the error in the overall effectiveness, ϕ, that might be caused by this Biot number error. Ti-6Al-4V is predicted to allow for a better Biot number match, better simulating Inconel at engine conditions in a low temperature experiment. In this research, we utilized geometrically identical models constructed of Ti-6Al-4V and Inconel 718 to evaluate the error in ϕ that might occur through using an actual engine nickel alloy part at experimental conditions. While the Ti-6Al-4V model has nearly perfectly matched Biot number, the Inconel model's value was 73% higher. The theoretically more Biot number appropriate Ti-6Al-4V model produced area averaged ϕ values that differed by only 0.01 from its Inconel counterpart. These results suggest that typical nickel superalloy turbine components may be tested at low temperature without the use of a surrogate material.
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