Flow boiling heat transfer of zeotropic mixture R1234yf/R32 inside a horizontal multiport tube

The flow boiling heat transfer and pressure drop of zeotropic binary mixture R1234yf/R32 were experimentally investigated inside a horizontal multiport tube with rectangular minichannels. Local heat transfer coefficients were quantified under mass fluxes in the range 50–400 kgm−2s−1, heat fluxes in the range 5–20 kWm−2, and circulation compositions of 80/20 and 50/50mass%. The obtained heat transfer coefficient of the mixtures were compared with those of pure components under the same experimental conditions. The heat transfer of the mixtures was strongly influenced by mass flux, vapor quality, and mass fraction, whereas the influence of heat flux on heat transfer was small. The heat transfer coefficients of the mixtures were lower than those of the pure components under most conditions owing to mass diffusion resistance and temperature glide; however, the heat transfer coefficients of the mixtures were same or higher than those of R1234yf at high mass flux and high vapor quality regions. The frictional pressure drops of the mixtures increased with increasing mass flux, vapor quality, and mass fraction of R1234yf. The database encompassing more than 900 and 190 for boiling heat transfer coefficient and frictional pressure drop were compared with available previous correlations. Previous correlations underestimated the heat transfer coefficients of the mixtures, especially for data with higher temperature glide and dominant forced convective heat transfer. The proposed correlation shows good agreement with the heat transfer coefficients of the R1234yf/R32 mixtures with mean and mean absolute deviations of −5.0% and 10.3%, respectively.