Flow boiling of carbon dioxide: Heat transfer for smooth and enhanced geometries and effect of oil. state of the art review

Abstract

This paper presents a state-of-the-art review on flow boiling of carbon dioxide, including experimental studies and correlations for smooth and enhanced tubes, with pure CO2 and CO2/lubricant mixtures. Specifically, 5223 CO2 heat transfer coefficient data in smooth tubes are collected, and the effect of the operating conditions is discussed. Additional 883 data points in microfin tubes and 1184 experimental heat transfer coefficients in smooth tubes with CO2/oil mixture are also collected, and the influence of the microfin structure and of the oil presence on the heat transfer mechanism is analyzed.The statistical analysis has highlighted that the CO2-based correlation of Fang et al. is very accurate (MAE = 5.1%) for the smooth tube database, whereas the heat transfer coefficients in microfin tubes are satisfactorily predicted (MAE = 30.5%) with the model of Mehendale. Among the available correlations for CO2/oil mixture in smooth tubes, the method of Gao et al. provides the highest accuracy (MAE = 63.2%).