A hybrid transient step-heating heat transfer measurement technique using heater foils and liquid-crystal thermography

A transient heat transfer technique using a heating foil and liquid crystals is described. The basic idea is a step-heating technique, eliminating the local heat flux and the surface temperature during the data reduction. Nonuniformities in the heating pattern are allowed and calibration of the liquid crystals is no longer necessary. They are used as an indicator of an isotherm only. The heat transfer coefficient is deduced from two time measurements. The laminar and turbulent boundary layer flows over a flat plate were tested to verify the applicability and accuracy of the method.