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

• Published in: The International journal of heat and fluid flow 2003-02, Vol.24 (1), p.23-28
• Main Authors: Owen, J.Michael, Newton, Paul J, Lock, Gary D
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Physics; Thermal instruments, apparatus and techniques; Thermochromic liquid crystal; Thermometry; Transient heat transfer; Uncertainties
• ISSN: 0142-727X; 1879-2278
• DOI: 10.1016/S0142-727X(02)00207-2

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, Φ h , 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 Φ h 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.