Flow boiling heat transfer coefficients and pressure drop of FC-72 in microchannels

The two-phase pressure drop and heat transfer coefficients of FC-72(C6F14) in two multi-ported rectangular microchannels with hydraulic diameters of 61 and 278 μm were measured by varying heat flux from 0.6 to 45.1 kW/m2 and mass flux from 188 to 1539 kg/m2 s. Direct heating using a DC power supply provided a heating load to the test section. The pressure drop increased with increasing vapor quality and mass flux. The heat flux negligibly affected the pressure drop under identical mass flux and vapor quality conditions, indicating that most of the pressure drop was caused by friction. When the vapor quality exceeded 0.2–0.4, the heat transfer coefficient decreased with increasing vapor quality due to early dry-out of liquid film on the channel surface. In addition, the comparison between the predicted pressure drop and heat transfer coefficient by the existing correlations and the measured values was presented.