超临界CO2-水耦合传热机理及试验研究OA

Under the background of the"dual carbon"goals,exploring new pathways for industrial restructuring,reducing carbon emissions,improving energy efficiency,and developing new high-quality productivity for CO2 high-energy utilization has become a research focus.To determine the mechanism of CO2 phase-change-induced cracking and expand its engineering applications,this study investigates the safety and environmental advantages of CO2 based on its multiphase characteristics and energy-utilization potential.A numerical gas-water coupling model is established.Using CO2 at 25℃as the research object,a simulation scheme is designed to examine different water temperatures as heat-carrying fluids,thereby revealing the CO2-water heat-transfer mechanism under hydrothermal-CO2 coupling.Furthermore,the heat and mass transfer characteristics of two-phase flow are analyzed by a CO2-water enhanced tube-type heat-exchanger test.The results show that as the hydrothermal-fluid temperature increases,the CO2 heating rate increases proportionally:for every 1℃increase in water temperature,CO2 temperature increases by 0.9℃.The water-stream temperature gradually decreases as CO2 absorbs heat,and the dissipation temperature of the hydrothermal fluid is proportional to the CO2 absorption temperature.The heat-transfer coefficient of the hydrothermal fluid increases from 1 790 W/(m2·K)to 2 090 W/(m2·K)and continues to rise with higher initial water temperatures.The heat transfer coefficient of CO2 is positively correlated with that of the hydrothermal fluids.The CO2 phase-change heat-absorption temperature shows an exponential growth trend with increasing water temperature.The maximum internal CO2 pressure increases from 131 MPa to 199 MPa,undergoing sequential stages:thermal expansion of liquid CO2,thermal expansion of gaseous CO2,phase-change energization,and pressure stabilization.CO2 heat absorption is positively correlated with the initial water temperature,and the thermal power of the water-flow heat source increases with rising water temperature.The effectiveness of supercritical CO2-water convective heat transfer is verified through the establishment of correlation equations and experimental analysis.This research provides significance theoretical and engineering insights for energy-conversion applications under non-uniform heat-flow conditions,such as photothermal systems,boilers,and CO2 fracturing and storage.