CO2 and propane blends: Experiments and assessment of predictive methods for flow boiling in horizontal tubes

The CO2 and propane blends are an interesting alternative to solve technical and safety issues related to the use of pure CO2 or pure hydrocarbons. These mixtures of pure fluids are environmentally friendly and have a large glide, that affects remarkably heat transfer.In this paper a review of works and predictive methods on flow boiling of wide-boiling mixtures is first presented. Experiments during flow boiling in a smooth horizontal tube with an internal diameter equal to 6.00 mm of CO2 and propane mixtures (with 83.2/16.8% and 70.0/30.0% in mass concentrations) are reported. The experiments are related to the following operating ranges: mass fluxes from 200 to 350 kg m−2 s−1, heat fluxes from 10 to 20.2 kW m−2, temperatures of the mixture from 6.9 to 14.0 °C in the whole range of vapor qualities.An assessment of predictive methods based on the present and independent databases is reported.