Unified correlation for heat transfer during boiling in plain mini/micro and conventional channels

A correlation is presented for predicting heat transfer coefficients during saturated boiling prior to critical heat flux in mini/micro channels as well as channels of conventional sizes in horizontal and vertical upward flow. The correlation is verified with a database that includes channels of various shapes (round, rectangle, triangle), fully or partially heated, horizontal and vertical downflow, diameters 0.38 to 27.1 mm, 30 fluids (water, CO₂, ammonia, halocarbon refrigerants, organics, cryogens), reduced pressure 0.0046 to 0.787, and mass flux 15 to 2437 kg m^?2s^?1. The new correlation predicts the 4852 data points from 137 data sets from 81 sources with a mean absolute deviation of 18.6 %. Several other correlations were also compared with the same database; all had significantly higher deviations.