Yun et al. [6] were concerned with flow boiling heat transfer
characteristics in rectangular multi-channels with hydraulic diameters
ranging from 1.08 to 1.54 mm. Working fluids tested were
CO2 and R-134a. Generally, the average heat transfer coefficient
of CO2 increased by around 53% as compared with that of R-
134a. The effect of heat flux on heat transfer coefficient was much
more obvious for CO2 than for R-134a. The dry-out phenomenon
was promoted by an increase in mass flux and it was also noted
that the effect of mass flux on heat transfer coefficient was less sig-