Transient heat transfer measurements using thermochromic liquid crystal. Part 2: Experimental uncertainties

In Part 1 of this two-part paper, an “exponential-series technique” was used to calculate heat transfer coefficient, h, for the so-called slow transient case where it is not possible to generate a step-change in the air temperature. Small uncertainties in the measured temperatures can, however, create large uncertainties in the calculated value of h, and the amplification parameter, Φh, is defined as the ratio of the relative uncertainty in h to the relative uncertainties in the temperatures. Using an uncertainty analysis, theoretical expressions for Φh are found for the slow transient case, and these expressions are in excellent agreement with values computed using a Monte Carlo method. The results provide guidance in the selection of design parameters for an experiment and for the calculation and minimisation of the uncertainty in h.