物理学报2024，Vol.73Issue(2)：156-165,10.DOI:10.7498/aps.73.20231142
流动方向对超临界二氧化碳流动传热特性的影响
Effect of flow direction on heat transfer and flow characteristics of supercritical carbon dioxide
摘要
Abstract
This work is devoted to investigating the difference in flow and heat transfer characteristics between vertical upward flow and horizontal flow of supercritical carbon dioxide(sCO2)based on the pseudo-boiling theory and the experimental parameters:mass flux G = 496-1100 kg/m2s,heat flux qw = 54.4-300.2 kW/m2,and pressure P = 7.531-20.513 MPa.The differences in flow and heat transfer characteristics between horizontal upward tube and vertical upward tube are compared at different mass fluxes,heat fluxes and pressures fully.Finally,unlike the classical treatment of flow and heat transfer for supercritical fluid,single-phase fluid assumption is abandoned,instead,the pseudo-boiling theory is introduced to deal with the flow transfer and heat transfer of sCO2 in the two tubes.Supercritical fluid is regarded as a multiphase structure in this work,including a vapor-like layer near the wall and a liquid-like fluid in tube core.The results are indicated below.1)In terms of heat transfer,the inner-wall temperature of the vertical upward tube and the bottom generatrix of horizontal tube are basically the same under normal heat transfer mode.When the heat transfer deterioration occurs in the vertical upward tube,larger supercritical boiling number(SBO)will cause the wall temperature peak of the vertical upward tube to be much higher than the wall temperature at top generatrix of the horizontal tube at the corresponding enthalpy.The SBO(SBO = 5.126×10-4)distinguishes between normal heat transfer deterioration and heat transfer deterioration in the vertical upward tube.In the horizontal tubes,SBO dominates the maximum wall temperature difference between the top generatrix and the bottom generatrix.Comparing with vertical upward tubes,higher qw/G is required for the heat transfer deterioration of supercritical fluid in the horizontal tubes under the same pressure.2)In terms of flow,the increase in slope of pressure drop in the vertical upward tube is due to the orifice contraction effect.The mechanism that dominates the variation of pressure drop in the horizontal tube is the flow stratification effect,and we show that Froude number Frave can be the similarity criterion number to connect the temperature difference between the top and bottom generatrix of horizontal tube and the pressure drop.The analysis suggests that mechanisms governing horizontal flow and vertical flow of sCO2 are different in heat transfer deterioration mode.For the vertical flow,the SBO plays a leading role,while for the horizontal flow,the Fr plays an indispensable role.关键词
超临界二氧化碳/流动传热/拟沸腾/传热恶化Key words
supercritical carbon dioxide/flow heat transfer/pseudo-boiling/heat transfer deterioration引用本文复制引用
程亮元,徐进良..流动方向对超临界二氧化碳流动传热特性的影响[J].物理学报,2024,73(2):156-165,10.基金项目
国家自然科学基金重点项目(批准号:52130608)和国家自然科学基金创新研究群体科学基金(批准号:51821004)资助的课题. Project supported by the Key Program of the National Natural Science Foundation of China(Grant No.52130608)and the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51821004). （批准号:52130608）
