【作者】 黄超；

【导师】 杨龙滨；

【作者基本信息】 哈尔滨工程大学 ， 动力工程及工程热物理， 2024， 硕士

【摘要】 基于“双碳”目标和低碳减排等相关政策背景,有机工质冷凝换热的机理研究以及强化传热技术的研发等方向对我国提高能源利用效率、降低环境污染、实现能源高质量发展具有重要意义。本文针对螺旋管管内强化换热研究的不足,自主设计并搭建了有机工质分液冷凝实验台,开展了分液螺旋管内R245fa流动冷凝强化换热实验研究,重点讨论了螺旋管结构和分液结构对换热管的气液分离性能、冷凝换热系数和冷凝压降的影响,为分液螺旋管的强化换热研究提供理论基础。主要研宄内容及结论如下:(1)以分液螺旋管为研究对象,开展了螺旋管的气液分离性能、冷凝换热系数和冷凝压降在不同流动工况下的变化规律相关研究,对比研究了管型和分液装置对其换热性能的影响。实验结果表明:在工质质量流量为100 kg/(m~2·s)时,可实现有效分液的范围最大,对应的入口干度为0.104-0.928。分液螺旋管相较于螺旋管有着的更大冷凝换热系数和更小的冷凝压降,得到的最大综合评价因子为1.79。分液螺旋管相较于分液竖直管有着更大冷凝换热系数和更大的冷凝压降,得到的最大综合评价因子为1.44。(2)以分液螺旋内肋管为研究对象,开展了螺旋内肋管的气液分离性能、冷凝换热系数和冷凝压降在不同流动工况下的变化规律相关研究,对比研究了螺旋螺距和内肋表面对其换热性能的影响。实验结果表明:分液螺旋内肋管的螺旋螺距越大,管内冷凝换热系数和管内冷凝压降越大,螺距为110 mm时得到最大的冷凝换热系数7158.06W/(m~2·K)和压降14.08 k Pa。内肋表面会增大螺旋管的冷凝换热系数和冷凝压降,同时扩大螺旋管的有效分液的工况范围。其综合评价因子在扩大的有效分液的工况范围得到极大提高,得到最大综合评价因子1.38。(3)以分液螺旋管为研究对象,开展了分液装置内气液分离效果随质量流量、入口干度和分液孔孔径变化的可视化研究,对比研究了分液孔孔径、孔数和孔排列对其气液分离性能和冷凝换热系数的影响。实验结果表明:孔径的增大会降低其有效分离对应的入口干度,分液孔径为2 mm时存在最大有效分离范围0.106-0.89和最大分液效率0.99。分液孔数为3时存在最大有效分离范围0.034-0.89和最大分液效率0.994。不同孔排列的有效分离范围有所差距,但差距不大。有效分离范围的改变直接影响分液效率,进而影响冷凝换热系数,分液效率越大,冷凝换热系数越大。更多还原

【Abstract】 Based on the"double carbon"goal and the related policy background of low-carbon emission reduction,the research on the mechanism of condensation heat transfer of organic working medium and the research and development of enhanced heat transfer technology are of great significance for improving energy utilization efficiency,reducing environmental pollution and achieving high-quality energy development in China.Aiming at the shortcomings of enhanced heat transfer in spiral tube,this paper independently designed and built an organic working medium gas-liquid separation and condensation experimental platform,and carried out experimental research on R245fa flow condensation enhanced heat transfer in spiral tube of gas-liquid separation,focusing on the influence of spiral tube structure and gas-liquid separation structure on gas-liquid separation performance,condensation heat transfer coefficient and condensing pressure drop of heat exchange tube.It provides a theoretical basis for the research of enhanced heat transfer in the helical tube of gas-liquid separation.The main research contents and conclusions are as follows:(1)Taking the gas-liquid separation spiral tube as the research object,relevant studies were carried out on the gas-liquid separation performance,condensation heat transfer coefficient and condensation pressure drop of the spiral tube under different flow conditions,and the influence of the tube type and gas-liquid separation device on its heat transfer performance was compared.The experimental results show that when the mass flow rate of working medium is 100 kg/(m~2·s),the maximum range of effective gas-liquid separation can be achieved,and the corresponding inlet dryness is 0.104-0.928.Compared with the spiral tube,the gas-liquid separation spiral tube has a larger condensing heat transfer coefficient and a smaller condensing pressure drop,and the maximum comprehensive evaluation factor is1.79.The gas-liquid separation spiral tube has a larger condensing heat transfer coefficient and a larger condensing pressure drop than the gas-liquid separation vertical tube,and the maximum comprehensive evaluation factor is 1.44.(2)Taking the gas-liquid separation spiral inner ribed tube as the research object,relevant studies were carried out on the gas-liquid separation performance,condensing heat transfer coefficient and condensing pressure drop of the spiral inner ribed tube under different flow conditions,and the effects of spiral pitch and inner rib surface on its heat transfer performance were compared.The experimental results show that the larger the spiral pitch of the inner rib tube of the gas-liquid separation spiral,the larger the condensing heat transfer coefficient and condensing pressure drop in the tube.When the pitch is 110 mm,the maximum condensing heat transfer coefficient is 7158.06W/(m~2·K)and the pressure drop is14.08k Pa.The surface of the inner rib will increase the condensing heat transfer coefficient and condensing pressure drop of the spiral tube,and expand the working range of the effective gas-liquid separation of the spiral tube.The comprehensive evaluation factor is greatly improved in the extended operating range of effective gas-liquid separation,and the maximum comprehensive evaluation factor is 1.38.(3)Taking the gas-liquid separation spiral pipe as the research object,a visual study was carried out on the gas-liquid separation effect in the gas-liquid separation device with the mass flow rate,inlet dryness and the aperture of the liquid separation hole.The effects of the aperture,number and arrangement of the liquid separation hole on the gas-liquid separation performance and the condensation heat transfer coefficient were compared.The experimental results show that the increase of the pore diameter will reduce the inlet dryness corresponding to the effective separation.When the pore diameter of the separation liquid is 2 mm,the maximum effective separation range is 0.106-0.89 and the maximum atmospheric liquid separation efficiency is 0.99.The maximum effective separation range is 0.034-0.89 and the maximum atmospheric liquid separation efficiency is 0.994 when the number of liquid separation holes is 3.The effective separation range of different pore arrangements is different,but the difference is not large.The change of the effective separation range directly affects the gas-liquid separation efficiency,and then affects the condensation heat transfer coefficient.The greater the gas-liquid separation efficiency,the greater the condensation heat transfer coefficient.更多还原