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Does back cooling improve human thermal comfort in warm environments?A device for heat conduction by the semiconductor Peltier effect

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Building Simulation 2024年第8期17卷 1253-1271页

作者： Mengyuan He Hong Liu Lianggen Shao Baizhan Li Yuxin Wu Joint International Research Laboratory of Green Building and Built Environments(Ministry of Education) Chongqing UniversityChongqingChina National Centre for International Research of Low-carbon and Green Buildings(Ministry of Science and Technology) Chongqing UniversityChongqingChina School of Civil Engineering and Architecture Zhejiang Sci-Tech UniversityHangzhouChina

The hot environment and the metabolic heat of commuting in summer caused individual overheating and intense thermal *** cooling presents huge potential for optimizing thermal *** study investigates the performance of a back cooling device,based on the semiconductor Peltier effect,in improving thermal comfort after summer *** studied one case without cooling,and three cases with surface temperatures of the cooling device of 29,27,and 25℃using a simulated summer commute at a moderate activity *** results showed that thermal sensation,perceived sweating rate,and skin temperature decreased markedly in the cooling cases compared to the non-cooling case,with the changes being most notable in the lower back,in contact with the cooling *** decrease in overall thermal sensation and mean skin temperature was approximately 0.52 score and 0.31℃on average,respectively,with a 1.71 score increase in overall thermal *** contend that the surface temperature of local contact cooling devices should not be lower than 22℃to minimize local *** cooling devices present a huge potential for building energy-savings at ambient air temperature exceeding 30℃.Moreover,the functional paradigms for individual comfort predict improved comfort performance in future *** study contributes to the understanding on the well-being and physiological recovery of individuals after a summer commuting.

关键词： back cooling heat conduction summer commuting thermal comfort prediction

Interaction effects on heat conduction and thermal stress in an infinite elastic plane with two circular holes

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Applied Mathematics and Mechanics(English Edition) 2021年第2期42卷 223-234页

作者： Kun SONG Deshun YIN Haibing YANG P.SCHIAVONE College of Mechanics and Materials Hohai UniversityNanjing 211100China School of Civil Engineering and Transportation South China University of TechnologyGuangzhou 510641China Department of Mechanical Engineering University of AlbertaEdmontonAlberta T6G 1H9Canada

Numerous researches have focused on the physical behavior of an elastic material in the vicinity of a single hole under the assumption that the interaction effects arising from the introduction of multiple holes remain negligible if the holes are placed sufficiently far from each *** an effort to understand hole interaction effects on heat conduction and thermal stress,we consider the case when two circular holes are embedded in an infinite elastic material and use complex variable methods together with numerical analysis to obtain solutions describing temperature and elastic fields in the vicinity of the two circular *** results indicate that the interaction effects on temperature distribution and stress strongly depend on the relative size of the two holes and the distance placed between them but not on the actual size of the holes.

关键词： heat conduction temperature field thermal stress interaction effect two circular holes

Lightweight diamond/Cu interface tuning for outstanding heat conduction

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Carbon Energy 2023年第12期5卷 229-240页

作者： Wenjie Dou Congxu Zhu Xiwang Wu Xun Yang Wenjun Fa Yange Zhang Junfeng Tong Guangshan Zhu Zhi Zheng Henan Key Laboratory of Diamond Optoelectronic Materials and Devices Key Laboratory of Materials PhysicsMinistry of EducationSchool of Physics and MicroelectronicsZhengzhou UniversityZhengzhouChina Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province College of Chemical and Materials EngineeringXuchang UniversityXuchangChina Work-Station of Zhongyuan Scholars of Henan Province Henan Huanghe Whirlwind Co.Ltd.ChanggeChina Key Laboratory of Polyoxometalate and Reticular Material Chemistry of Ministry of Education Northeast Normal UniversityChangchunChina

With rapid developments in the field of very large-scale integrated circuits,heat dissipation has emerged as a significant factor that restricts the high-density integration of *** to their high thermal conductivity and low thermal expansion coefficient,diamond/Cu composites have attracted considerable attention as a promising thermal management *** this study,a surface tungsten carbide gradient layer coating of diamond particles has been realized using comprehensive magnetron sputtering technology and a heat treatment ***/Cu composites were prepared using high-temperature and high-pressure *** results show that,by adjusting the heat treatment process,tungsten carbide and di-tungsten carbide are generated by an in situ reaction at the tungsten–diamond interface,and W–WC–W_(2)C gradient layer-coated diamond particles were *** diamond/Cu composites were sintered by high-temperature and high-pressure technology,and the density of surface-modified diamond/Cu composites was less than 4 g cm^(-3).The W–WC–W_(2)C@diamond/Cu composites have a thermal diffusivity as high as 331 mm^(2)s^(-1),and their thermal expansion coefficient is as low as 1.76×10^(-6)K^(-1).The interface coherent structure of the gradient layer-coated diamond/copper composite can effectively improve the interface heat transport efficiency.

关键词： coherent interface diamond composite heat conduction surface modification

New analytic solutions to 2D transient heat conduction problems with/without heat sources in the symplectic space

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Applied Mathematics and Mechanics(English Edition) 2022年第8期43卷 1233-1248页

作者： Dian XU Xinran ZHENG Dongqi AN Chao ZHOU Xiuwen HUANG Rui LI State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanicsand International Research Center for Computational MechanicsDalian University of TechnologyDalianLiaoning Province116024China

The two-dimensional(2D)transient heat conduction problems with/without heat sources in a rectangular domain under different combinations of temperature and heat flux boundary conditions are studied by a novel symplectic superposition method(SSM).The solution process is within the Hamiltonian system framework such that the mathematical procedures in the symplectic space can be implemented,which provides an exceptional direct rigorous derivation without any assumptions or predetermination of the solution forms compared with the conventional inverse/semi-inverse *** distinctive advantage of the SSM offers an access to new analytic heat conduction *** results obtained by the SSM agree well with those obtained from the finite element method(FEM),which confirms the accuracy of the SSM.

关键词： heat conduction heat source symplectic superposition method(SSM)

Multi-domain physics-informed neural network for solving heat conduction and conjugate natural convection with discontinuity of temperature gradient on interface

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Science China(Technological Sciences) 2022年第10期65卷 2442-2461页

作者： WANG TongSheng WANG ZhiHeng HUANG Zhu XI Guang School of Energy and Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Deep learning has been increasingly recognized as a promising tool in solving kinds of physical problems beyond powerful approximations. A multi-domain physics-informed neural network(mPINN) is proposed to solve the non-uniform heat conduction and conjugate natural convection with the discontinuity of temperature gradient on the interface. Local radial basis function method(LRBF) is applied to compute the case without the analytical solution and is regarded as the benchmark *** physical domain matches a private neural network and all neural networks are connected by the shared information of temperature and heat flux on the interface. Joint training and separate training are utilized to minimize the loss function, which usually consists of the residual of boundary conditions, interface conditions and governing equations. Joint training minimizes the sum of all losses from neural networks with one shared optimizer, while separate training owns its private optimizer. Local adaptive activation function(LAAF) is used to accelerate the convergence and acquire a lower loss value when compared with its fixed counterpart. The numerical experiments on three types of residual points, uniform, Gauss-Lobatto and random, are conducted and it can be concluded that the uniform residual points can obtain the most accurate solution than the random and Gauss-Lobatto. Joint training is more accurate than the separate training when the number of residual points is relatively small,while the separate training performs better than the joint training for the large number of residual points. Numerous test cases on multi-domain heat transfer and fluid flow show the accuracy of the proposed m PINN. Local and global heat transfer rates show good agreements with the results from LRBF. Excepting the forward problems, the thermal conductivity ratio, the constant source and the characteristic parameters of natural convection are accurately learned from sparsely distributed data points.

关键词： multi-domain physics-informed neural network heat conduction conjugate natural convection interface condition

Anomalous energy diffusion and heat conduction in one-dimensional system

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Chinese Physics B 2010年第5期19卷 393-398页

作者：李海彬李珍 Department of Applied Physics Zhejiang University of Technology

We propose a new concept, the centre of energy, to study energy diffusion and heat conduction in a one-dimensional hard-point model. For the diatom model, we find an anomalous energy diffusion as （x2） - tβ with β = 1.33, which is independent of initial condition and mass rate. The present model can be viewed as the model composed by independent quasi-particles, the centre of energy. In this way, heat current can be calculated. Based on the theory of dynamic billiard, the divergent exponent of heat conductivity is estimated to be α = 0.33, which is confirmed by a simple numerical calculation.

关键词： energy diffusion heat conduction one-dimensional hard-point model

Two exact solutions of the DPL non-Fourier heat conduction equation with special conditions

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Acta Mechanica Sinica 2009年第2期25卷 205-210页

作者： Youtong Zhang Changsong Zheng Yongfeng Liu Liang Shao Chenhua Gou School of Mechanical and Vehicular Engineering Beijing Institute of Technology 100081 Beijing China School of Mechanical-Electronic and Automobile Engineering Beijing University of Civil Engineering and Architecture100044 Beijing China

This paper presents two exact explicit solutions for the three dimensional dual-phase lag （DLP） heat conduction equation, during the derivation of which the method of trial and error and the authors＇ previous experiences are utilized. To the authors＇ knowledge, most solutions of 2D or 3D DPL models available in the literature are obtained by numerical methods, and there are few exact solutions up to now. The exact solutions in this paper can be used as benchmarks to validate numerical solutions and to develop numerical schemes, grid generation methods and so forth. In addition, they are of theoretical significance since they correspond to physically possible situations. The main goal of this paper is to obtain some possible exact explicit solutions of the dual-phase lag heat conduction equation as the benchmark solutions for computational heat transfer, rather than specific solutions for some given initial and boundary conditions. Therefore, the initial and boundary conditions are indeterminate before derivation and can be deduced from the solutions afterwards. Actually, all solutions given in this paper can be easily proven by substituting them into the governing equation.

关键词： Exact solution Dual-phase lag Non-Fourier Benchmark solution heat conduction

A phase-field study on the oxidation behavior of Ni considering heat conduction

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Acta Mechanica Sinica 2016年第5期32卷 881-890页

作者： Chao Wang Shigang Ai Daining Fang State Key Laboratory for Turbulence and Complex Systems Peking UniversityBeijing 100871China Institute of Engineering Mechanics Beijing Jiaotong UniversityBeijing 100044China Beijing Institute of Technology Beijing 100081China

Phase-field modeling approach has been used to study the oxidation behavior of pure Ni when considering heat conduction. In this calculation, the dependence of the coefficient of the Cahn–Hilliard equation Lc on the temperature T was considered. To this end, high-temperature oxidation experiments and phase-field modeling for pure Ni were performed in air under atmospheric pressure at 600,700, and 800？C. The oxidation rate was measured by thermogravimetry and Lc at these temperatures was determined via interactive algorithm. With the Lc-T relationship constructed, oxidation behavior of Ni when considering heat conduction was investigated. The influence of temperature boundaries on the oxidation degree, oxide film thickness, and specific weight gain were discussed. The phase-field modeling approach proposed in this study will give some highlights of the oxidation resistance analysis and cooling measures design of thermal protection materials.

关键词： High-temperature oxidation Phase-field approach heat conduction Thermogravimetry analysis Nickel

Fuzzy finite difference method for heat conduction analysis with uncertain parameters

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Acta Mechanica Sinica 2014年第3期30卷 383-390页

作者： Chong Wang Zhi-Ping Qiu Institute of Solid Mechanics Beihang University

A new numerical technique named as fuzzy finite difference method is proposed to solve the heat conduction problems with fuzzy uncertainties in both the phys- ical parameters and initial/boundary conditions. In virtue of the level-cut method, the difference discrete equations with fuzzy parameters are equivalently transformed into groups of interval equations. New stability analysis theory suited to fuzzy difference schemes is developed. Based on the parameter perturbation method, the interval ranges of the uncertain temperature field can be approximately predicted. Subsequently, fuzzy solutions to the original difference equations are obtained by the fuzzy resolution theorem. Two numerical examples are given to demonstrate the feasibility and efficiency of the presented method for solving both steady-state and transient heat conduction problems.

关键词： heat conduction Fuzzy uncertainties Finitedifference method Parameter perturbation Stability analysis