Fluid-solid heat transfer analysis: In situ validation and calibration of a boiling meter using a combined experimental-numerical heat transfer approach

Abstract

To study and quantify the heat transfer between wall and fluid at the transition regime between natural convection and nucleate boiling, a boiling meter, incorporating two heat fluxmeters coupled with thermocouples, along with other components, was designed and built. This paper explores the methods used to calibrate and characterize this sensor under in situ conditions. The boiling meter has been experimentally investigated in a test cell for two configurations regarding the orientation of its largest faces with gravity: one vertical and the other one horizontal. The experimental results showed inconsistencies when compared to physical expectations. To address this problem, calibration of the boiling meter, using numerical simulations is performed with the CFD software Star-CCM+. These simulations were achieved considering the heat transfer at the scale of the whole test cell. The temperature and the heat transfer rate calculated at the two surfaces at the borders of each heat fluxmeter were compared with the experimental results. It was found that one thermocouple provided temperatures closer to those calculated at the outer end of a heat fluxmeter, while the other was closer to those at the inner end. Moreover, the numerical results revealed that the temperatures and fluxes at the boiling meter-liquid interface differed from the experimental measurements. The reasons for this discrepancy were identified and analyzed. As a result, the combination of experimental and simulation approaches allowed for a deeper understanding of the heat transfer measurements and results.