共查询到20条相似文献,搜索用时 15 毫秒
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Chein-Shan Liu 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(4):305-323
We consider an inverse problem for numerically estimating a spatial-dependence heat conductivity α(x) in T t (x, t) = ?[α(x)T x ]/? x + h(x, t), 0 < t < t f , 0 < x < ?; α(x) is assumed to be a continuous function of x, and α(?) is given. An iterative Lie-group adaptive method (LGAM) is developed, which can be used to find α(x) at the spatially discretized locations x i , requiring only a few measured temperature data at a final time t f as a target to select a suitable value of the parameter r ∈ [0, 1] appearing in the present method. The new method has three advantages in that no a priori information of the heat conductivity function is required, only a few extra data are measured, and it is robust againt noise. The accuracy and efficiency of the present method are confirmed by comparing the estimated results with some exact solutions. 相似文献
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M. Vynnycky 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(4):275-292
Although the numerical solution of parabolic partial differential equations (PDEs) is widely documented, the effect of discontinuous boundary conditions on numerical accuracy is not. This article employs the Keller box finite-difference method to study the effect of such discontinuities when solving the linear one-demensional transient heat equation. We demonstrate that this formally second-order-accurate scheme can lose accuracy, but that an analytical understanding of the behavior of the solution helps in providing an accuracy-restoring formulation. Benchmark computations are presented that will provide guidance in the numerical solution of nonlinear parabolic PDEs for which there are no closed-form analytical solutions. 相似文献
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Cheng-Ying Lo 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(2):130-146
This article presents a numerical approach using the hybrid differential transform/finite-difference method to study heat transfer in a thin film exposed to ultrashort-pulsed lasers based on the hyperbolic two-step model. The governing equations are transformed from the time domain into the spectrum domain using the differential transform method and then discretized in the space domain by the finite-difference method. The numerical solutions are obtained through a recursive process. The results show that even though the electron/lattice temperature is at equilibrium at only a couple hundred degrees, the maximum electron temperature can reach as high as several thousand degrees. 相似文献
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Sergei Yakovenko 《Journal of Dynamical and Control Systems》2006,12(3):433-449
We give a simplified proof and an improvement of a recent theorem of A. Grigoriev, placing an upper bound for the number of
roots of linear combinations of solutions of systems of linear equations with polynomial or rational coefficients.
To Yulij Sergeevich Ilyashenko on his 60th birthday.
2000 Mathematics Subject Classification. 34C08, 34C10, 34M10.
Gershon Kekst professorial chair in Mathematics. 相似文献
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S.K. Sahu P.K. Das Souvik Bhattacharyya 《International Journal of Thermal Sciences》2009,48(11):2100-2107
Conduction-controlled rewetting of two-dimensional objects is analyzed by the Heat Balance Integral Method (HBIM) considering three distinct regions: a dry region ahead of wet front, the sputtering region immediately behind the wet front and a continuous film region further upstream. The HBIM yields solutions for wet front velocity, sputtering length and temperature field with respect to wet front. Employing this method, it is seen that heat transfer mechanism is dependent upon two temperature parameters. One of them characterizes the initial wall temperature while the other specifies the range of temperature for sputtering region. Additionally, the mechanism of heat transfer is found to be dependent on two Biot numbers comprising a convective heat transfer in the wet region and a boiling heat transfer in the sputtering region. The present solution exactly matches with the one-dimensional analysis of K.H. Sun, G.E. Dix, C.L. Tien [Cooling of a very hot vertical surface by falling liquid film, ASME J. Heat Transf. 96 (1974) 126–131] for low Biot numbers. Good agreement with experimental results is also observed. 相似文献
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This paper deals with the two-dimensional, non-homogeneous boundary value problem for static, isotropic and thermoelastic material occupying an infinitely long cylinder with a rectangular cross-section. The cylinder is surrounded by a given temperature and subjected to variable pressures at its boundaries. We deal with static, uncoupled, linear thermoelasticity. The equations of heat conduction and mechanical problem are considered separately. The technique of the finite Fourier transform is used for the solution. The thermoelastic behavior, due to an internal heat generation within the domain, is discussed. The results for displacement and stresses have been computed from the Airy stress function and are illustrated graphically. 相似文献
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Optimal Homotopy Asymptotic Solutions for Nonlinear Ordinary Differential Equations Arising in Flow and Heat Transfer due to Nonlinear Stretching Sheet
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Optimal homotopy asymptotic method (OHAM) is used to obtain solutions for nonlinear ordinary differential equations (ODEs) arising in fluid flow and heat transfer at a nonlinear stretching sheet. The solutions for skin friction and temperature gradient for some special cases are tabulated and compared with the available numerical results in the literature. Moreover, OHAM is found to be very easy to use and the technique could be used for solving coupled nonlinear systems of ordinary differential equations arising in science and engineering. 相似文献
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基于蒙特卡洛法的单室火灾热辐射计算 总被引:1,自引:0,他引:1
根据CFAST软件模拟简单房间着火后热烟气层温度及高度的变化情况,采用蒙特卡洛法计算热烟气层对房间地板面及地板中心1m2面积上的平均热辐射通量.计算时,分别假设烟气层的辐射能力集中于热烟气层的下表面,或烟气层为温度均匀的灰体,结果表明两种假设的计算结果相近.根据两种假设计算出的地板面上的热辐射通量,预测出室内发生轰燃的时间分别是640s和700s,与CFAST软件的预测结果665s相近.评估中引入热辐射对人体的伤害判据,其结果也可以用来估算安全疏散时间. 相似文献
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S.K. Sahu P.K. Das S. Bhattacharyya 《International Journal of Heat and Mass Transfer》2006,49(25-26):4978-4986
A two region conduction-controlled rewetting model of hot vertical surfaces with a constant wet side heat transfer coefficient and negligible heat transfer from dry side is solved by the Heat Balance Integral Method (HBIM). The HBIM yields a simple closed form solution for rewetting velocity and temperature distribution in both dry and wet regions for given Biot numbers. Using this method it has been possible to derive a unified relationship for one-dimensional object and two-dimensional slab and rod. The effect of convection is expressed by an effective Biot number whose exact value depends on the geometry and process parameters. The solutions are found to be exactly the same as reported by Duffey and Porthouse [R.B. Duffey, D.T.C Porthouse, The physics of rewetting in water reactor emergency core cooling, Nucl. Eng. Des. 25 (1973) 379–394], Thompson [T.S. Thompson, An analysis of the wet-side heat transfer coefficient during rewetting of a hot dry patch, Nucl. Eng. Des. 22 (1972) 212–224] and Sun et al. [K.H. Sun, G.E. Dix, C.L. Tien, Cooling of a very hot vertical surface by falling liquid film, ASME J. Heat Transfer 96 (1974) 126–131; K.H. Sun, G.E. Dix, C.L. Tien, Effect of precursory cooling on falling-film rewetting, ASME J. Heat Transfer 97 (1974) 360–365]. Good agreement with experimental results is also observed. 相似文献
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Traditional condensing air-conditioning systems consume large amounts of energy in hot and humid areas,and it is difficult to achieve simultaneous control of temperature and humidity.A combined absorption refrigeration(AR) and liquid desiccant dehumidification(LDD) air-conditioning system based on cascade utilization of low-grade heat source is proposed.The system can realize independent control of temperature and humidity and carry out profound recovery of low-grade heat sources.Under the desig... 相似文献
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为解决工农业干燥过程中存在的干燥效率低、能耗高等问题,同时充分利用生产过程中产生的中低品位热能,设计了一种可控温湿度的中低温热源干燥系统,干燥系统由加热系统、排湿换气系统、温湿度控制系统和干燥室组成。介绍了其干燥工艺,分析了其运行性能和能耗情况,通过试验数据分析发现该干燥系统气流温度和速度分布均匀、能耗低,系统在整个干燥过程中的干燥速率为0.122 kg/(kg∙h),整个过程的能耗因子为391.2 kJ/kg。系统适用于以地热能和工业余热等中低温热能为热源的工农业干燥过程。 相似文献
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以输配能耗最小为目标,室内舒适和建筑节能相关要求为约束条件,利用MATLAB的优化工具箱,对地表水水源热泵输配系统的优化模型进行研究,确定影响地表水水源热泵输配系统能耗的主要因素。应用此方法对水源热泵实验系统进行了应用分析,得到了系统随负荷率变化的冷却水和冷冻水变流量优化运行方案。对于大部分时间处于部分负荷运行的系统,优化运行比定流量运行可减少能耗10%以上。该优化模型能方便地应用于实际工程,为输配系统的设计和运行提供最佳参数,实现随负荷变化的流量调控,从而有效降低水源水输配能耗,提高系统能效。 相似文献
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Operation strategies of Ground Source Heat Pump System(GSHPS) such as continuous or intermittent approaches have been extensively studied. In this work, a novel strategy was proposed to maximize the energy efficiency of GSHPS. In this approach, the buildings was first air-conditioned by the preheating/precooling mode and the rest thermal load was covered by the heat pump(HP) mode. The system performance can then be optimized by considering the combination of these two operating modes. A case stu... 相似文献
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The present article aims to extend a previous numerical study on the natural convection process in a square enclosure with a vertical eccentric square heat source (cylinder) [1]. Here, we investigated buoyancy-induced convective flow and heat transfer for horizontal and diagonal eccentric displacement in a square cylinder. Numerical studies are performed for Rayleigh numbers in the range 103–106, using our recently developed flexible forcing IB–thermal lattice Boltzmann method scheme [1]. Detailed analysis of isotherms, streamlines, and Nusselt number distribution as functions of Rayleigh number and eccentricity is provided in this paper. 相似文献