A generalized correlation for two-phase forced flow heat transfer

Abstract

A generalized correlation for forced convection vaporization heat transfer is suggested which is valid for both vertical and horizontal channels with a fully wetted perimeter. It represents, with a mean absolute deviation of 12.9%, experimental data for nine different fluids (water, freons, cryogens) in the following main parameter ranges: pressure 0.61–30.4 bar, mass flow rate 50–2690 kg m −2s −1, vapour quality 0.017–1.00, channel diameters 1.63–41.3 mm. The vaporization heat transfer rate is found to depend on the thermal conductivity of channel wall material. A universal criterion for convective boiling is suggested which determines the dominant mode of heat transfer of the two main ones: nucleate boiling or evaporation. Recommendations for calculating heat transfer to a two-phase flow in the presence of both heat transfer mechanisms are given.