Flow boiling of non-azeotropic mixture R32/R1234ze(E) in horizontal microfin tubes

• HTC of flow boiling R32 alone is higher than that of R1234ze(E) in horizontal microfin tube.
• R32/R1234ze(E) yielded a significantly lower HTC than either of the single components.
• HTC is minimized at 0.2/0.8 by mass, where the mole fraction difference is maximized.
• Based on Stephan, Momoki et al., and Thome, a predicting correlation was proposed.

Flow boiling of a potential refrigerant R32/R1234ze(E) in a horizontal microfin tube of 5.21 mm inner diameter is experimentally investigated. The heat transfer coefficient (HTC) and pressure drop are measured at a saturation temperature of 10 °C, heat fluxes of 10 and 15 kW m−2, and mass velocities from 150 to 400 kg m−2 s−1. The HTC of R1234ze(E) is lower than that of R32. Degradation in the HTC of the R32/R1234ze(E) mixture is significant; the HTC is even lower than that of R1234ze(E). The HTC is minimized at the composition 0.2/0.8 by mass, where the temperature glide and the mass fraction distribution are maximized. A predicting correlation based on Momoki et al. (1995) associated with the correction methods of Thome (1981) to consider the mass transfer resistance and Stephan (1992) to consider the additionally required sensible heat is proposed and validated with the experimental results.