Influence of the heat flux in mixture boiling: experiments and correlations

Heat transfer at nucleate pool boiling of the binary and ternary refrigerant mixtures R404A, R407C and R507 at the outside of a horizontal tube with emery ground surface has been investigated in a wide range of pressures and heat fluxes. Together with experimental data of Bednar and Bier for wide boiling ethane/n-butane mixtures, the results of these comparatively narrow boiling mixtures are used to investigate the influence of heat flux q on the heat transfer coefficient alpha as predicted by various correlations for nucleate boiling of mixtures. At comparatively high saturation pressures with experimental alpha-values markedly smaller than the molar average of the pure components, the alpha,q-relationships predicted differ significantly from the experimental, particularly for wide boiling mixtures. (C) 1998 Elsevier Science Ltd and IIR.