Condensation heat transfer and pressure drop characteristics of CO2 in a microchannel

• Flow complexity is dominant factor in condensation with microchannels.
• Existing models highly overpredicted condensation heat transfer coefficient of CO2.
• The Mishima and Hibiki model was suitable for predicting pressure drop.

The condensation heat transfer coefficient and pressure drop of CO2 in a multiport microchannel with a hydraulic diameter of 1.5 mm was investigated with variation of the mass flux from 400 to 1000 kgm−2s−1 and of the condensation temperature from −5 to 5 °C. The heat transfer coefficient and pressure drop increased with the decrease of condensation temperature and the increase of mass flux. However, the rate of increase of the heat transfer coefficient was retarded by these changes. The gradient of the pressure drop with respect to vapor quality is significant with the increase of mass flux. The existing models for heat transfer coefficient overpredicted the experimental data, and the deviation increased at high vapor quality and at high heat transfer coefficient. The smallest mean deviation of ±51.8% was found by the Thome et al. model. For the pressure drop, the Mishima and Hibiki model showed mean deviation of 29.1%.