Research On Enhanced Convective Heat Transfer Based On The Representation Of Freeform Surfaces With Channel Structures

As electronic devices with high power consumption,high integration,high complexity,and extreme operating conditions continue to evolve,the impact of temperature on system performance is becoming increasingly critical.Due to its advantages in simplicity,multifunctionality,efficiency,and flexibility,the convective heat exchanger has emerged as an ideal solution for tackling high-temperature challenges.Structural design,as a passive strategy for enhancing convective heat transfer,effectively optimizes the interplay between fluid dynamics and thermal exchange,enabling efficient and reliable thermal management.However,current structural design methods have certain limitations,most notably in two areas: first,in research methodology,as existing design frameworks have not fully explored the potential of characteristic structures in enhancing convective heat transfer;and second,in geometric structure,as current structure design methods often limit designs to single or limited degrees of freedom,thereby constraining the optimization of convective heat transfer performance at both global and local levels.Therefore,it is essential to scrutinize and improve existing structural design methods to gain a more comprehensive understanding of the complex interactions between characteristic structures and convective heat transfer,and to further unlock the potential of multi-degree-of-freedom designs in enhancing both global and local convective heat transfer capabilities.Focusing on the basic structural features of overall convective heat transfer layouts,including serpentine channels,twisted channels,wavy channels,dendritic channels,finned channels,and cross-sections,this research proposes a series of innovative thermal structure design methods through structural modeling and optimization strategies,and further constructs optimization models for achieving optimal thermal performance.The main work carried out is as follows:(1)A design method for enhancing convective heat transfer in free-shape serpentine channels has been proposed.Systematic structural modeling was conducted for the serpentine channels,covering various structural features and associated degrees of freedom,including circular,quadrilateral,channel trajectory,and channel twisting.By introducing Bernstein-Bézier functions and geometric spatial mapping,a design method was developed that allows for the reshaping of serpentine channel structural features under given constraints.Furthermore,through orthogonal experimental design and range analysis,the study delved into the impact of different local structural features on thermal and hydraulic performance.Ultimately,experimental results validated the effectiveness of the proposed method,providing new theoretical and practical foundations for the design of efficient heat exchange serpentine channels.(2)A design method for enhancing convective heat transfer in free-shape twisted channels has been proposed.Building on the twisting features in serpentine channels,the study delves into the optimal structural design and corresponding heat transfer phenomena of twisted channels for enhanced heat transfer.Single-channel and double-channel basic structural models are used,and rational Bernstein-Bézier functions are introduced to enhance the degrees of freedom in cross-sectional types and size variations.From a modeling perspective,the study analyzes the impact of different preset twisting spaces on heat transfer capabilities and employs a gradient-free optimization algorithm,using average temperature and standard deviations of temperature as objective functions,to achieve optimal design of the model.Additionally,in the double-channel model,numerical simplification of constraints and a step-by-step optimization strategy are proposed to avoid geometric,mesh,and numerical computation errors during the optimization process.Through numerical iterative optimizations,compared to the initial single-channel design,the average temperatures of the target surfaces for the single-channel and double-channel models have decreased by 7.21 K(2.25%)and 15.56 K(4.89%)respectively.The standard deviations of temperature have decreased by 2.22 K(59.68%)and 1.97 K(47.43%)respectively.Ultimately,experimental results validate the effectiveness of the proposed method,providing modeling theory and optimized design for efficient thermal management in twisted channels.(3)A design method for enhancing convective heat transfer in free-shape wavy channels has been proposed.Systematic structural modeling was conducted for wavy channels to enhance their heat transfer performance,utilizing cubic spline functions,wavelet functions,truncated functions,and rational Bernstein-Bézier functions to describe amplitude,wavelength,waveforms,and cross-sectional features.Horizontal wavy channels and radial wavy channels were taken as the subjects of study,and average temperature and standard deviations of temperature were used as objective functions.Optimal designs for both types of channels were obtained through the use of non-dominated sorting genetic algorithms and Pareto front graphs.A comparison was also made with empirically-based uniform wavy channels,and the results showed that non-uniform wavy channels outperform uniform wavy channels in terms of heat transfer performance.Specifically,based on overall thermal performance ranking: non-uniform horizontal wavy design(VHWC-22)> uniform radial wavy design(URWC)> ≈ non-uniform radial wavy design(VRWC-30)> uniform horizontal wavy design(UHWC);according to temperature uniformity ranking: nonuniform radial wavy design(VRWC-30)> non-uniform horizontal wavy design(VHWC-22)> uniform radial wavy design(URWC)> uniform horizontal wavy design(UHWC).Ultimately,experimental results validated the effectiveness of the proposed method,providing modeling theory and optimized design for efficient heat exchange in wavy channels.(4)A biomimetic tree-like channel design method for enhancing convective heat transfer has been proposed.Systematic structural modeling was conducted to improve the heat transfer performance of tree-like channels,encompassing structural elements such as branch angles,branch lengths,the number of branches,branch levels,channel patterns,elliptical crosssectional shapes and sizes,as well as channel twisting.A three-dimensional spatial topological framework for biomimetic tree-like channels was constructed,and methods for segmenting models within branches were further derived.Based on the modeling approach,a planar cold plate model commonly used in battery thermal management was designed.Average temperature and standard deviations of temperature were used as objective functions,and optimal design for the cold plate was obtained using non-dominated sorting genetic algorithms and Pareto front analysis.The results indicate that there can be a maximum reduction of 5.91 K(1.75%)in the average temperature and 2.06 K(23.54%)in the temperature standard deviation of the target surface.Ultimately,experimental results validated the effectiveness of the proposed method,providing modeling theory and optimized design for efficient heat exchange in tree-like channels.(5)A method for secondary modeling and optimization design of fin channel topological boundaries has been proposed.Based on the fin structures generated through topological optimization,secondary modeling and optimization design were conducted on their topological boundaries.Bernstein-Bézier functions were utilized for segmentation and fitting,and three optimization frameworks were defined to further iteratively optimize explicit geometric boundaries,that is,normal search,radial search,and rectangular search.By comparing with current typical cold plate models,the effectiveness of the proposed method was validated,and an in-depth exploration was conducted on the impact of secondary optimization of topological boundaries in enhancing heat transfer.(6)Through the optimization design of obtained foundational structures or overall formats,localized optimization designs were conducted on serpentine,tree-like,and fin and parallel channels cold plates.The quantitative evaluations of the performance disparities among different designs were carried out,scrutinizing the thermal and comprehensive performance of various cold plate designs with different layouts under different Reynolds numbers,and providing qualitative conclusions concerning general heat transfer principles.