摘要
本文对水平管道内超临界压力下甲烷的流动与传热过程进行了数值模拟,得到了5 MPa下质量流率范围为200~400 kg/(m^2·s),热流密度范围为100~400 kW/m^2工况下的传热规律。提出了以热质比r(热流密度与质量流率的比值)为判据来预测异常传热行为(传热强化和传热恶化相继发生):在r>0.5 kJ/kg工况下,传热出现异常行为;在r≤0.5 kJ/kg工况范围内,异常传热行为消失,换热系数沿程呈下降趋势。在此基础上,对典型传热工况进行了深入的机理分析。结果表明:二次环流涡心的偏移是传热异常的主要原因,环流涡心向管壁偏移可使边界层减薄从而强化传热,环流涡心向轴线偏移则使边界层增厚、发生“湍流层流化”,从而恶化传热;湍动能的增大是换热系数增大、换热进入恢复区的主要原因,随着二次环流减弱换热进入正常传热阶段。
The flow and heat transfer of supercritical pressure methane in a horizontal tube was studied by numerical method within the mass flux range of 200-400 kg/(m^2·s) and heat flux range of 100~400 Kw/m^2 under the pressure of 5 Mpa in this paper.The ratio(r),which is referred to as the rate between heat flux and mass flux,was proposed as a new criteria of special heat transfer: when the ratio(r) is above 0.5 Kj/kg,heat transfer enhancement and deterioration occur continuously,which belongs to special heat transfer;While the special heat transfer behavior disappears and heat transfer coefficients decrease along the tube in the condition of r≤0.5 Kj/kg.Major causes of special heat transfer are revealed through further mechanism analysis to two typical cases: the vortex deviation of secondary flow is the main reason causing special heat transfer,when the vortex of secondary flow shifts to the tube wall,the boundary layer will be weaken,which enhances the heat transfer,and when the vortex shifts from the wall to the axis,the boundary layer will be thicken and turbulent flow will laniinarize,which can deteriorate the heat transfer.The increase of turbulent kinetic energy is the major reason of heat transfer recovery and normal heat transfer will begin with the weaken of the secondary flow.
作者
杨帆
王国付
姜文全
陈树军
潘斌
陈保东
YANG Fan;WANG Guo-Fu;JIANG Wen-Quan;CHEN Shu-Jun;PAN Bin;CHEN Bao-Dong(College of Petroleum Engineering,Liaoning Shihua University,Fiishun 113001,China;College of Pipeline and Civil Engineering,University of Petroleum (Huadong),Qingdao 266580,China;Liaoning Institute of Science and Technology,Benxi 117004,China)
出处
《工程热物理学报》
EI
CAS
CSCD
北大核心
2019年第8期1921-1927,共7页
Journal of Engineering Thermophysics
基金
国家自然基金青年基金资助项目(No.61602228)
辽宁省教育厅科学研究经费项目(No.L2019024)
关键词
传热异常
热质比
二次环流
湍流层流化
湍动能
special heat transfer
ratio of heat flux to mass flux
secondary flow
laminarization of turbulent flow
turbulent kinetic energy
