Two-phase pressure drop during CO₂ vaporization in horizontal smooth minichannels

Pressure drop experiments for a natural refrigerant vaporization of CO₂ were performed in horizontal minichannels. The test section was made of stainless steel tubes with inner diameters of 1.5 mm and 3.0 mm and with lengths of 2000 and 3000 mm. This test section was uniformly heated by applying electric current directly to the tubes. Experiments were performed at inlet saturation temperatures of -10, -5 and 10 °C, mass flux ranges from 200 to 600 kg m^-2 s^-1 and heat flux ranges from 10 to 30 kW m^-2. The current study showed the significant effect of mass flux, tube diameter, and saturation temperature on the pressure drop. The experimental results were compared against 13 existing two-phase pressure drop prediction methods. A new pressure drop prediction method based on the Lockhart-Martinelli method was developed with 9.41% mean deviation.