This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Void fraction measurements are obtained using high speed video for the condensation of R404A in
tubes of diameter 0.508, 1.00, and 3.00 mm. Experiments were conducted on refrigerant R404A throughout
the entire condensation quality range (0.05 < x < 0.95) at varying mass fluxes (200 ≤ G ≤ 800 kg m-2 s-1) and
saturation temperatures from 30 to 60°C (0.38 ≤ pr ≤ 0.77). These high pressures are representative of actual
operation of air-conditioning and refrigeration equipment. The influence of saturation temperature on void
fraction is most pronounced in the quality range 0.25 < x < 0.75. In addition, it was found that the influence
of mass flux on void fraction was negligible for all saturation temperatures and tube diameters investigated.
A new drift flux void fraction model is developed to predict void fraction for condensing flows in
microchannels and compared with the R404A data and R134a void fraction data from Winkler et al. (2012a).
Overall the model is able to predict 92.3% of the R404A data and 81.6% of all refrigerant data within 25%
