Applicability and practical concerns of lock-in thermography for measurement of heat transfer coefficients

Starting with a brief review on the measurement of heat transfer coefficient by periodic thermal perturbation, the analysis on the extendibility of the method to the time-averaged scenario, in general, is followed by the impact of environmental (i.e., where the periodic perturbing heat flux is imposed) heat transfer coefficient on the infeasible region where the model fails, and the corresponding location of the minimum sensitivity in the operational space of the measurement. We conclude the present work with a discussion based on the multiobjective optimization in which the systematic error in the measured phase lag, the sensitivity (the derivative of heat transfer coefficient with respect to phase lag), the signal-to-noise ratio, and the temperature fluctuation of the working fluid that follows the periodic perturbing heat flux are to be minimized simultaneously.