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Simultaneous measurement of liquid film characteristics and heat transfer in annular two-phase flow is a major experimental challenge. In this study, we implement an innovative integrated infrared (IR) heater and liquid film electrical-conductance sensor in combination with high-speed IR thermography, which results in an accurate, synchronized and co-located measurement of liquid film characteristics and local heat transfer at the heated surface in diabatic annular two-phase flow. The measurements reveal that disturbance waves have a significant effect on the instantaneous heat transfer response in nominally-steady vertically upward annular flow of steam-water mixtures. Although the heat flux applied at the wall is constant in time, the passage of the waves causes significant periodic oscillations of the local heat transfer coefficient and wall superheat in the forced convective evaporation regime, which are reported in this study.

Nucleate boiling is important in many energy systems including light water reactors. Currently significant efforts are underway to develop mechanisticmodels for nucleate boiling based on computational fluid dynamics (CFD). Development and validation of these models require new high fidelity experimental data with high spatial and temporal resolutions. Previous work such as has measured temperature distributions and diameter of a growing bubble. It is important to obtain further information, such as bubble shape during growth and after departure, and velocity profiles in the liquid.This paper presents an improved experimental approach for synchronized measurement of these data.