Experimental Investigation Of Condensation Heat Transfer With A Large Percent Of CO₂

The global environmental issue with the core of climate change is increasinglyserious. To avoid the progressive and irreversible deterioration of environment, theCO2based greenhouse gas emission reduction has become hot-topic of internationalsociety. Carbon capture and storage (CCS) is one important technology option thatcan limit and reduce global carbon dioxide emissions. According to the calcium-basedsorbent method undergoing carbonation and calcination reactions, the decompositionof CaCO3occurs simultaneously with high concentration CO2. The introducing steamas weep gas to dilute CO2under low CO2partial pressure has benefit to thecalcination rate, while the gas mixture containing released CO2and steam exits thereactor for further purification. So, the research of steam condensation with highconcentration CO2has important significance.Condensation experiment is performed to investigate the effects of CO2underthe conditions of gas mass concentration of11.2%～89.8%and different vapormixture velocity and surface subcooling. The condensation heat transfer coefficientreduces greatly with the CO2increases because of the CO2gas is carried with vaportoward the interface and accumulates as a strong resistance. The vapor boundary layerresistance and condensed water increases as inlet CO2increases while the heattransfer coefficient is only200W/m2K when the CO2concentration reaches89.8%.Higher steam flow results in higher condensation heat transfer coefficient. However,the effect of velocity decreases as the mass concentration of CO2and surfacesubcooling increases. Besides, the result of local heat transfer characteristics researchshows the different heat transfer rates in tube location. The effect of surfacesubcooling and vapor velocity is more obvious on top of tube which has higher heattransfer coefficient. The derived empirical formula under different velocities has anestimated maximum error of±20%compared with experimental solution.