Effect of micro-grooves on the two-phase pressure drop of CO2 in a mini-channel tube

• Pressure drop in a grooved mini-channel can be estimated using hydraulic diameter.
• Smaller hydraulic diameter of the grooved channel made the pressure drop higher.
• Pressure drop during evaporation could be well estimated using adiabatic data.
• Most of the two-phase pressure drop models showed a reasonable prediction.

The pressure drop characteristics of CO2 have been experimentally investigated for a mini-channel tube with and without micro rectangular grooves. The multiple mini-channels have an inner diameter of 0.8 mm and the grooves have a rectangular cross section (0.1 × 0.2 mm). The pressure drop was measured for a saturated liquid phase and two-phase. Using the hydraulic diameter, the pressure drop in the grooved mini-channel can be successfully estimated with the correlations used for smooth channels. Because of a smaller hydraulic diameter, the pressure drop of the grooved channel was found to be about 1.3 times and 1.1–1.45 times greater than that of the smooth channel, for liquid and two-phase, respectively. The experimental results were compared with widely used two-phase pressure drop models. Most of the models showed the mean absolute error of 17–35% for the smooth channel and 13–32% for the grooved channel.