B311 RELATION BETWEEN HEAT TRANSFER AND FRICTIONAL PRESSURE LOSS FOR FLOW BOILING OF WATER

概要

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To investigate the momentum and heat transfer analogy for flow boiling, heat transfer coefficient and pressure drop of water flowing in a round tube with an internal diameter of 8.03 mm were simultaneously measured. A correlation of frictional pressure loss was obtained from the experimental data by modifying the correlation of Chisholm-Laird as Φ_l^2=1+17/X_<tt>+5/X_<tt>^2. From the comparison of the data of heat transfer coefficient, h_<TP>/h_<Lf>/(1-α), with correlations of the frictional pressure loss, Φ_l^2,it was found that the analogy between heat transfer and fluid friction did not hold for the flow boiling. The difference between them was considerably large and represented by an experimental factor of K ranging from 1.5 to 2.2. A turbulent eddy diffusivity model was applied to the forced convective evaporation heat transfer to an annular liquid film flow. The calculated results agreed well with the experimental data when the eddy diffusivity of heat, ε_H, proposed by Mudawwar and El-Masri for the freely falling turbulent liquid films with evaporation, was applied.
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