Experimental Determination of Heat Transfer Coefficients in Oscillatory Two-Phase Annular Flow

Upward concurrent two-phase annular flow occurs in many evaporating, condensing and reacting flows. In vaporizing flow systems involving high heat flux in multiple parallel channels, thermohydraulic instabilities are frequent, resulting in pulsing or oscillating flow. The work describe here presents a unique data set involving wall temperature, film thickness and pressure drops. Making these measurements simultaneously allows comparison of published heat transfer coefficient correlations with experimentally determined HTCs. One published model relates HTC to the wall shear, τ, and film thickness, δ. The δ-τ model consistently under-predicts the measured heat transfer coefficient. Further, as pulse frequency increases, both the film thickness and heat transfer coefficient respond less to the oscillating flow.