Accurate Measurements of the Local Heat Transfer Coefficients along the Dedicated Test section

With regard to the new experimental test facility for the advanced heat transfer and fluid flow studies, which has recently been designed and built at Reactor Engineering Division of Jožef Stefan Institute, special calculation procedure has been adopted for accurate local Heat Transfer Coefficient calculation (HTC). In this procedure, knowing the precise values of the local heat flux, the fluid and the wall surface temperature is of paramount importance. On one hand, the wall temperature is measured directly. On the other hand, the local heat flux distribution is deduced from the secondary fluid temperature gradient profile and the saturation temperature is calculated either from the thermal balance on the secondary side or from the calculated distribution of the measured pressure at the inlet and outlet of the test section. In both cases, the fluid temperature is calculated iteratively. Moreover, error propagation analysis has been studied to identify and to work on key parameters that are affecting the accuracy of our measurements. In this context, CFD analysis has been carried out in wide range of test conditions to better account for the expected discrepancy between the actual and the measured wall surface temperature distribution. The calculation procedure and the experimental setup are presented in the present paper.