高真空度低质量流率下蒸汽水平管内凝结特性研究

发布时间：2018-03-15 08:55

  本文选题：水平管内蒸汽凝结　切入点：传热系数　出处：《大连理工大学》2014年博士论文　论文类型：学位论文

【摘要】：随着我国经济的发展,淡水的需求量越来越大,水资源短缺日益严重。《国家“十二五”科学和技术发展规划》中要求加快海水淡化技术的发展,特别是低温多效蒸发(MED)海水淡化技术。水平管内凝结现象是低温多效蒸发海水淡化装置中的主要传热过程之一,低温多效蒸发海水淡化装置中的管内凝结现象具有小传热温差、低质量流率和较严格的流动阻力要求等特点,开展对水平管内凝结的研究,探索强化传热方式,将为开发具有自主知识产权的海水淡化设备提供重要的技术依据和理论基础。 水平管内凝结广泛存在于人们的生产和生活中。研究水平管内凝结传热,对提高换热器性能具有重要意义。为系统深入地研究水平管内凝结过程,本文对水平管内流型、传热系数分布和流动阻力进行了实验研究和理论分析。主要研究内容包括： (1)建立水平管内凝结流动与传热实验台,对入口质量流率0-8kg/(m2.s)、入口蒸汽饱和温度45～70℃的水平管内凝结流动与传热进行了实验研究。 (2)根据对凝结液流动的观测实验,分析了蒸汽流量、干度、蒸汽饱和温度对液位角的影响；对空隙率和液位角的计算模型进行了探讨,并归纳出空隙率和液位角计算的经验公式。 (3)根据对水平管内凝结传热系数的实验研究,分析了分层流型对水平管内传热的影响；讨论了传热温差、蒸汽饱和温度、入口质量流率和不凝结气体含量等因素对传热过程的影响；分析了管内传热系数沿管圆周方向的分布与液位角之间的关系；探讨管内凝结传热系数沿管长方向下降的原因；并分析了凝结液侧和蒸汽侧管内传热系数的变化规律。 (4)根据对水平管内流动阻力的实验研究。分析了入口质量流率、蒸汽雷诺数、蒸汽饱和温度和传热温差对管内摩擦系数的影响；讨论了蒸汽与凝结液界面表面粗糙度与气液间剪切力的关系。 (5)综合流型观测、传热系数和流动阻力测量结果,讨论了入口质量流率、传热温差和蒸汽饱和温度对水平管凝结传热量的影响,分析最优出口干度的变化规律。 (6)本文在双极坐标系下,采用低雷诺数模型,计算了水平管内的液位高度、流动阻力和速度场分布,并分析了气相和液相的物性变化对液位高度和流动阻力的影响。
[Abstract]:With the development of China's economy, the demand for fresh water is increasing, and the shortage of water resources is becoming more and more serious. The 12th Five-Year Plan for Scientific and technological Development of China calls for speeding up the development of seawater desalination technology. The condensation phenomenon in horizontal tube is one of the main heat transfer processes in low temperature multi-effect evaporative seawater desalination unit, and the condensation phenomenon in low temperature multi-effect evaporation seawater desalination device has small heat transfer temperature difference. With the characteristics of low mass flow rate and strict flow resistance, the study of condensation in horizontal pipe and the exploration of enhanced heat transfer mode will provide important technical and theoretical basis for the development of seawater desalination equipment with independent intellectual property rights. Condensation in horizontal tube is widely existed in people's production and life. It is very important to study condensation heat transfer in horizontal tube to improve the performance of heat exchanger. In order to study the condensation process in horizontal tube systematically, the flow pattern in horizontal tube is studied in this paper. The distribution of heat transfer coefficient and flow resistance are studied experimentally and theoretically. The condensation flow and heat transfer in a horizontal tube are studied experimentally at the inlet mass flow rate of 0 ~ 8 kg / m ~ 2 路s ~ 2 路s ~ (-1) and the inlet vapor saturation temperature at 4570 鈩，

本文编号：1615318