高频超轻多孔回热器脉动换热与流动特性研究

Based on the status of research about thermoacoustic regenerator and the excellent properties of ultra-lightporous fiber materials and structures, the acoustic characteristics such as flow resistivity, porosity, structural constant, effective heat conduction and integrated heat transfer coefficient, sound velocity, complex characteristic impedance, complex propagation parameters and viscoelastic waveare studied. Using fractal theory, pulsating enhanced heat transfer, transfer function, Forchheimer correction method, experimental measurement and other means,the microstructures of ultra - light porous regenerators were described by using fractal dimension and fiber volume fraction as the main parameters of micro and the fractal model of Scheerenboski was established. Then the non-linear thermal bonding effect and the thermoacoustic effect excitation mechanism in the high-frequency regenerator are analyzed, and the design method of the acoustic and thermoacoustic conversion of the high-frequency multi-layer porous regenerator is studied with the bionic thinking. This is of great significance to improve the acoustic heat transfer conversioneffect of the regenerator, reduce its thermal viscous resistance, revealthe mechanism of the high-frequency porous media regenerator thermal energy and sound energy conversion and energy transport and the alternating flow characteristics and heat transfer characteristics of compressible fluid in different porous fiber micro-channel and the positive and negative temperature gradient.The study can provide a new idea of high-frequency regenerator,and new theories and new structures to evaluate its performance and characterize. The results of the research are of great value to all regenerative cryogenic refrigerators.

基于超轻多孔纤维材料和结构的优异特性及热声回热器现状，研究回热器中流阻率、孔隙率、有效导热和综合传热系数、声质点速度、复特性阻抗与复传播参数、粘弹性波等声学特性，采用分形理论、脉动传热、传递函数、Forchheimer修正方法、实验测量等手段，以分形维数和纤维体积分率为表征微空间结构主要参数，对超轻多孔回热器微结构进行描述，建立回热器谢尔宾斯基分形模型和脉动换热模型，分析高频回热器中非线性热粘效应及热声效应激发机制，以仿生学思维来寻找高频高效多层多孔回热器声热与热声转换设计方法，对提高回热器的声热传递转换效果，减少其热粘阻力，揭示高频多孔介质回热器中气--固脉动强化换热与流动机理、高频热声系统阻抗与相位匹配、以及可压缩流体在不同多孔纤维微细流道中传热与流动特性有重要意义。可提供高频回热器研究新思路、评价其性能表征新理论和新结构，课题成果对所有回热式低温制冷机均具有重要价值。

回热器是研制热声热机、低温制冷机及其性能提高的物质基础和保障。充分认识并正确对回热器性能进行表征，对热声热机及其相关设备的研究、生产和择优选用具有非常重要的实际意义。. 课题基于超轻多孔纤维材料和结构的优异特性及热声回热器现状，针对回热器中流阻率、孔隙率、有效导热和综合传热系数、声质点速度、复特性阻抗与复传播参数、粘弹性波等声学特性展开研究，采用分形理论、脉动传热、传递函数、Forchheimer修正方法、实验测量等手段，以分形维数和纤维体积分率为表征微空间结构主要参数，对超轻多孔回热器微结构进行描述，建立回热器谢尔宾斯基分形模型和脉动换热模型，分析高频回热器中非线性热粘效应及热声效应激发机制，以仿生学思维来寻找高频高效多层多孔回热器声热与热声转换设计方法，对提高回热器的声热传递转换效果，减少其热粘阻力，揭示高频多孔介质回热器中气--固脉动强化换热与流动机理、高频热声系统阻抗与相位匹配、以及可压缩流体在不同多孔纤维微细流道中传热与流动特性有重要意义。. 为提高超轻多孔回热器脉动换热与流动特性，以分形理论为依据，研究了回热器材料及结构对其整体换热特性的影响关系。结果表明：对于多孔回热器材料的传热，热量传递相当复杂，热量通过不规则固体骨架以及间隙中流动流体的对流与导热两种进行传递；不同的分形结构会影响回热器内的换热效果，科赫边界模型的换热效果更佳；脉动流的存在会在一定程度上影响介质温度、压力、速度场的分布，回热器的换热特性会随着脉动振幅和频率的增加而增大。课题研究提供了高频回热器研究新思路、评价其性能表征新理论和新结构，成果对所有回热式低温制冷机均具有重要价值。