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

作　　者：程亮元 徐进良[1,2] Cheng Liang-Yuan;Xu Jin-Liang(Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization,North China Electric Power University,Beijing 102206,China;Key Laboratory of Power Station Energy Transfer Conversion and System,Ministry of Education,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学,低品位能源多相流与传热北京市重点实验室,北京102206 [2]华北电力大学,电站能量传递转化与系统教育部重点实验室,北京102206

出　　处：《物理学报》2024年第2期192-201,共10页Acta Physica Sinica

基　　金：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。

摘　　要：本文基于拟沸腾理论研究了超临界二氧化碳(sCO_(2))在水平和垂直向上管中的流动和传热特性差异.比较了不同质量流量、热流密度和压力下水平管与垂直向上管的流动和换热特性差异.与以往超临界流体的经典单相流体假设不同,本文引入拟沸腾理论来处理sCO_(2)在两管中的流动和传热,将超临界流体视为多相结构,包括近壁区的类气层和管芯中的类液流体.结果发现,传热方面,在正常传热模式下垂直向上管内壁温和水平管底母线内壁温基本一致.当垂直向上管发生传热恶化时,垂直向上管的壁温峰值会随着超临界沸腾数(SBO)的增大超过对应焓值位置的水平管顶母线内壁温.垂直向上管中SBO区分了正常传热和传热恶化.而在水平管中,当弗劳得数小于100时,SBO主导顶底壁面最大壁温差.相比于垂直向上管,相同压力下的超临界流体在水平管内发生传热恶化需要更高的热流密度和质量流量的比值.流动方面,引起垂直向上管压降斜率增高的机理是孔口收缩效应.主导水平管压降变化的机理是分层效应,并用弗劳得数在水平管中顶底壁温差异与压降之间建立联系.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(sCO_(2))based on the pseudo-boiling theory and the experimental parameters:mass flux G=496-1100 kg/m^(2)s,heat flux qw=54.4-300.2 kW/m^(2),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 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 variati

关 键 词：超临界二氧化碳 流动传热 拟沸腾 传热恶化 

分 类 号：TK124[动力工程及工程热物理—工程热物理]