Two-phase pressure drops of CO2 are investigated in mini tubes with inner diameters of 2.0 and 0.98 mm and in microchannels with hydraulic diameters from 1.08 to 1.54 mm. For the mini tubes, the tests were conducted with a variation of mass flux from 500 to 3570 kg/m2s, heat flux from 7 to 48 kW/m2, while maintaining saturation temperatures at 0, 5, and 10°C. For the microchannels, mass flux was varied from 100 to 400 kg/m2s and heat flux was altered from 5 to 20 kW/m2. A direct heating method was used to provide heat flux into the refrigerant. The pressure drop of CO2 in the mini tubes shows very similar trends with those in large diameter tubes. Although the microchannel has a small hydraulic diameter, it shows a larger Chisholm parameter in two-phase multiplier. Based on the experimental data in this study, the Chisholm parameter in the Lockhart and Martinelli correlation is modified by considering diameter effects on the two-phase multiplier.
- Carbon dioxide
- Mini tubes
- Two-phase pressure drop
ASJC Scopus subject areas
- Mechanical Engineering
- Materials Science (miscellaneous)
- Physics and Astronomy (miscellaneous)