Pressure drop during condensation of R134a flowing inside a multiport minichannel

This paper is a continuation of the authors' previous work on the condensation of R134a flowing inside a multiport minichannel (Sakamatapan et al., 2013) [22]. The pressure drop's characteristics during condensation were investigated in an experiment for R134a flowing inside a multiport minichannel. The pressure drop characteristics were observed under mass flux range of 345-685 kg/m2, heat flux of 15-25 kW/m2, and saturation temperature of 35-45 °C. Two types of multiport minichannels having 14 channels, one with a 1.1 mm hydraulic diameter and another with 8 channels with a 1.2 mm hydraulic diameter, were designed as a counter flow tube in a tube heat exchanger. The results showed that the total pressure drop is dominated by the frictional pressure drop. The frictional pressure gradient increased with the augmentation of mass flux and vapor quality, but the increase of the saturation temperature and channel size play an important role in the decrease of frictional pressure gradient. On the other hand, the heat flux had an insignificant effect on the frictional pressure gradient. Moreover, the miniscale correlations were conducted to predict the frictional pressure gradient, and it was found that only the multiport minichannel correlations gave a reasonable result. A new two-phase friction factor correlation was proposed using the equivalent Reynolds number concept to predict the frictional pressure gradient during condensation.