【作者】 杨晨；

【导师】 杨龙滨； 王建志；

【作者基本信息】 哈尔滨工程大学 ， 动力工程（专业学位）， 2022， 硕士

【摘要】 利用有机朗肯循环发电技术将海底热液的热能转化为电能是解决深海设备供电问题的有效手段之一。影响有机朗肯循环的发电效率的因素之一是有机工质的种类选择,采用非共沸混合工质作为循环工质,其在相变过程中独特的温度滑移特性可以减小由传热温差导致的不可逆损失,提高系统发电效率。本文开展了非共沸混合工质及其纯组分工质流动沸腾换热和压降特性实验研究。为了明确非共沸混合工质流动沸腾换热的基本变化规律,自主搭建了有机工质流动沸腾换热实验系统,以R123、R245fa及二者的混合物作为工质进行流动沸腾特性实验研究,实验运行参数为质量流量21-37kg/m~2·s、热流密度13-19.6k W/m~2,并选用光滑面和金属泡沫两种加热面结构,对比分析加热面结构对换热性能的影响。R123和R245fa两种纯工质的流动沸腾实验结果表明:光滑加热面结构下,R123和R245fa的换热系数随运行参数的变化趋势相近,换热系数随着质量流量的增大而减小,随着热流密度的增大而增大,但R245fa的换热系数远高于R123的换热系数;在金属泡沫加热面结构下,两种工质的换热系数都远高于光滑加热面结构下的换热系数,大部分运行参数条件下,金属泡沫加热面结构下R245fa的换热系数随热流密度增大而增大,但在G=21kg/m~2·s条件下换热系数随着热流密度的增大先上升后下降;两种加热面结构下,较低质量流量条件下的压降总是最大的。组分比例为80/20%的非共沸混合工质R123/R245fa流动沸腾实验结果表明:与纯工质相比,混合工质的换热系数介于两种纯工质换热系数之间,换热系数在较高热流密度条件下的增幅比纯工质换热系数的增幅大;金属泡沫加热面结构下,在G=21kg/m~2·s条件下混合工质的换热系数同样随热流密度增大先上升后下降,下降点的热流密度比R245fa下降点的热流密度大,下降幅度也较小。较大质量流量时,压降随着热流密度的增大而增大,较小质量流量时,压降先增大后减小。对比分析不同组分比例非共沸混合工质的流动沸腾特性发现,随热流密度增大,R245fa组分比例越高的混合工质换热系数的增幅越大,35/65%和22/78%混合工质在q=19.6k W/m~2时的换热系数超过了同工况下R245fa的换热系数,且35/65%和22/78%混合工质的压降比78/22%的更小。更多还原

【Abstract】 Organic Rankine cycle power generation technology is one of the effective means to solve the power supply problem of deep-sea equipment.One of the factors affecting the power generation efficiency of the organic Rankine cycle is the selection of the type of organic working fluid.The non-azeotropic mixed working fluid is used as the circulating working fluid.The unique temperature slip characteristic of the non-azeotropic mixed working fluid in the phase transformation process can reduce the irreversible loss caused by the heat transfer temperature difference and improve the power generation efficiency of the system.In this paper,the flow boiling heat transfer and pressure drop characteristics of non-azeotropic mixed working fluid and its pure components are studied.In order to clarify the basic variation law of flow boiling heat transfer of non-azeotropic mixed working fluid,an experimental system of flow boiling heat transfer of organic working fluid was built independently.R123,R245fa and their mixture were used as working fluid to conduct experimental research on flow boiling characteristics.The experimental operating parameters were mass flow rate 21-37kg/m~2·s and heat flow density 13-19.6k W/m~2.Two heating surfaces,smooth surface and metal foam,were selected to compare and analyze the influence of heating surface structure on heat transfer performance.The flow boiling experiment results of R123 and R245fa pure working fluid show that:Under the smooth heating surface structure,the heat transfer coefficients of R123 and R245fa have similar trends with operation parameters.The heat transfer coefficients decrease with the increase of mass flow rate and increase with the increase of heat flow density,but the heat transfer coefficients of R245fa are much higher than those of R123.Under the metal foam structure of heating surface,both of the heat transfer coefficient is much higher than smooth and heating surface structure of the heat transfer coefficient,most of the operation parameters under the condition of metal foam under the structure of heating surface heat transfer coefficient of R245fa with heat flux density increases,but in G=21kg/m~2·s under the condition of heat transfer coefficient with the increase of heat flux decline after rising first;The pressure drop is always maximum at lower mass flow rate under both heating surfaces.The flow boiling experiment results of R123/R245fa non-azeotropic mixed working fluid with a component ratio of 80/20%show that the heat transfer coefficient of the mixed working fluid is between that of the pure working fluid and that of the pure working fluid,and the increase of the heat transfer coefficient is larger than that of the pure working fluid at higher heat flux density.Under the metal foam heating surface structure,the heat transfer coefficient of the mixed working fluid also increases first and then decreases with the increase of heat flux at G=21kg/m~2·s,and the heat flux at the decreasing point is larger and smaller than that at the decreasing point of R245fa.When the mass flow rate is larger,the pressure drop increases with the increase of heat flux,while when the mass flow rate is smaller,the pressure drop increases first and then decreases.It is found that the heat transfer coefficient of the mixed fluid with a higher proportion of R245fa increases with the increase of heat flow density.The heat transfer coefficient of 35/65%and 22/78%mixed fluid at q=19.6k W/m~2exceeds that of R245fa under the same working condition.The pressure drop of 35/65%and22/78%mixed fluid is smaller than that of 78/22%.更多还原