Critical heat flux of cyclohexane in uniformly heated minichannels with high inlet subcooling

• CHF increased with increasing mass velocity and decreasing heated length.
• Reducing channel diameter did not increase CHF values.
• CHF mildly increased with an increase in pressure at higher mass velocities.
• Experimental CHF data well agreed with those predicted by existed correlations.
• Corrected CHF correlation can predict CHF in the deviations of ±10%.

The critical heat flux (CHF) for flow boiling of cyclohexane was experimentally investigated in electrically heated minichannels with inside diameters of (1 and 2) mm, and heated lengths of (360 and 710) mm at mass velocities ranging from (318 to 1274) kg/m2 s, heat fluxes from (50 to 1000) kW/m2, and pressures of (1.0, 2.0, 3.0) MPa. Cyclohexane entered the test channel at ambient temperature of about 20 °C, equivalent to high subcooling of (162.1, 206.4 and 236.3) °C at (1.0, 2.0 and 3.0) MPa respectively. The critical vapor qualities ranged from −1.35 to 0.83. Results indicated that CHF of cyclohexane increased with increasing mass velocity and decreasing heated length. Reducing channel diameter at the same length-to-diameter ratio was proved to have no effects on CHF values of cyclohexane at the evaluated conditions. CHF mildly increased with an increase in pressure at higher mass velocities, but critical vapor quality always decreased with the increasing pressure. Experimental CHF data were compared with the Katto–Ohno (1984) correlation and Shah (1987) correlation. Good agreements were achieved between the experimental data and those predicted with most deviations not exceeding 30%. A corrected Katto–Ohno CHF correlation is developed to fit the current experimental data. Excellent agreement was obtained with all the deviations (whatever of saturation CHF or subcooled CHF) in the range of ±10% with RMS error of 5.35%.