日照作用对热源建筑自然通风影响的研究

参照变电站主变压器室，建立了双侧开口热源建筑数值模型，通过改变大气透过率（sunshine fraction）的大小改变日照强度，利用FL U EN T进行求解，考察日照作用对热源建筑自然通风流动的影响。计算结果表明：日照作用影响热源建筑室内外热量传递的大小和方向，当大气透过率为0．15时，室内外两侧传递热量达到平衡。较大的日照强度导致通风量增大，室内气流速度分布更均匀，日照作用下不同高度的气流温度受到的主要影响因素不同。     

间隔热源加热下新型热管冷板内部汽液两相流动与传热的数值模拟

为了有效解决阵列行波管的多热源、高热流散热问题，研制了一种结构全新的热管冷板。建立了热管冷板内部汽液两相流动与传热的两相流模型，并采用IPSA算法对间隔热源加热下热管冷板的内部流动和传热特性进行了数值模拟。通过数值模拟和试验验证，考察了该热管冷板的初步运行性能，为其实际应用提供了依据。图8表1参9     

煤矿供热热源探讨

在矿井生产过程中,如何选择热源是煤矿企业面临的一个现实问题。介绍了煤矿工业中常用的两种热源即燃煤锅炉和水源热泵,给出了两种热源的选型计算方法,并结合具体项目进行了比较和能耗分析,提出了煤矿行业在热泵利用中存在的问题,并给出了解决问题的途径,对于我国煤炭行业节能降耗具有一定的参考意义。     

控制容积平衡法在一维、稳态且含内热源导热微分方程中的应用

首先采用区域离散方法A和区域离散方法B分别划分计算网格节点,然后采用控制容积平衡法对某一维、稳态且含内热源导热微分方程进行了数值求解,并与其解析解（精确解）进行了比较.计算结果表明：控制容积平衡法物理意义明确,数值求解精度高,且随网格划分节点数的增加计算精度进一步提高;对于这两种网格划分方法,其网格节点处的离散方程推导均简单明了,且都具有统一的形式,因此对计算节点数增加的情况具有很大的适应性,有利于计算机编程实现.     

低温热源驱动的氨-水吸收式制冷循环分析

对一种低温热源驱动的氨－水吸收式制冷系统进行了计算和分析，这个系统的特点是对氨蒸汽进行两次吸收，用一部分冷凝氨液作为低压吸收器的冷却介质，增大了放气范围，使循环可以在低温热源的驱动下获得低制冷温度。     

地表水源热泵辅助热源节能效果的分析

介绍了地表水水源热泵工程中两种常用的辅助热源形式，指出辅助热源的布置形式影响着系统运行的经济性。推导出了两种形式下热泵系统单位小时运行费用，结合某实例说明采用后置式辅助热源的地表水源热泵系统运行费用小，具有节能的优越性。     

循环风作用下高温热源建筑内表面换热特性分析

采用数值模拟的方法，分析工业建筑在不同热源温度、循环风速和新风比条件下的气流特性和内表面换热特性。结果显示：天花板在整个建筑换热中的占比最大，并且随着热源温度和壁面温度差值的增大以及循环风速和新风比的减小，各表面的平均换热系数增大。同时，拟合关联式和模拟结果之间十分吻合，可以用于顶部循环风和水平新风及高温热源耦合作用下的工业建筑内表面的换热强度分析预测。     

有机朗肯循环工质热源转折温度的新求解法及应用

为获取热源和有机工质的最佳匹配规律,提高系统热力性能,提出求解工质热源转折温度的新方法及基于工质热源转折温度的工质与热源最优匹配新方法。首先,通过定义潜热熵差比推导出工质热源转折温度的理论公式,并采用蜻蜓算法进行精确求解;其次,与文献[14]对比,验证模型准确性;最后,对比工质热源转折温度与热源温度筛选最优工质。结果表明：选用的15种工质的热源转折温度与文献[14]的对比误差不超过1.62%,验证了工质热源转折温度求解公式的准确性;当热源温度确定时,选择热源转折温度小于热源温度的工质可获得最佳工况;当工质确定时,选择高于该工质热源转折温度的热源温度可获得最佳工况。     

开式横流热源塔传热传质特性分析

以开式横流热源塔为研究对象,建立塔体内传热传质数学模型,并采用Matlab软件对数学模型编程求解。根据实际工程的测试数据验证数学模型的准确性,进而运用该数学模型分析热源塔冬季传热传质的特性,并通过对空气流量、载冷剂流量、热源塔空气进口干球温度和含湿量、载冷剂进口温度的研究,帮助改善热源塔的换热性能。     

建筑冷热源优化选型模型

介绍单目标决策模型、多目标决策模型各自的理论基础及其在建筑冷热源优化模型中的应用,分析了两种模型各自的优劣。通过建筑冷热源火用分析研究,发现火用效率从质和量两方面分析系统能源利用情况,比传统的热平衡效率更具有科学性,提出建立空调冷热源系统的火用分析模型及其改进的多目标经济评价模型。     

矩形直肋散热器的散热量的计算方法

介绍了导热、对流与辐射同时存在时，计算矩形直肋散热器散热量的解析方法、数值解法，讨论了两种方法的物理意义和应用，并对两种方法得到的数据做了对比。     

Numerical Simulation of Fluid Flow and Heat Transfer in U-Shaped Microchannels

The numerical simulation of transport in complex microchannel systems for thermal management is considered, focusing on U-shaped microchannels. The simulation is carried out in conjunction with an experimental study. A physical system for fluid flow in U-shaped microchannels with heat generation at the bottom has been set up. This system approximates the use of microchannel flow for heat removal from electronic devices. Different numerical models are considered for system modeling and simulation. By comparing the results from these models and the obtained experimental data, it is found that the two channel model, which employs two channels with periodic boundary conditions, is the optimal model to simulate the overall heat transfer performance. Thus, the focus of the study is on the use of combined experimentation and numerical simulation for an accurate and realistic modeling of such complex microchannel systems, without excessive computations needed for simulating each microchannel of the system.     

A New Numerical Approach for Predicting the Two-Phase Flow of Refrigerants during Evaporation and Condensation

This article reports on four finite-volume–based numerical methods developed for predicting the one-dimensional two-phase flow of pure refrigerants in evaporators and condensers during change-of-phase processes. The methods differ in the physical assumptions considered at the interface separating the liquid and vapor phases and in the equation used to predict the variation of the refrigerant flow quality during change of phase. In all methods, numerical predictions are obtained via a locally iterative marching-type solution algorithm. Therefore, the models permit the prediction of the size of the pipe needed to achieve full evaporation/condensation of the saturated refrigerant. The effectiveness and robustness of the numerical procedures in predicting the flow and heat transfer characteristics are assessed by comparing results with published experimental data. Good agreement is obtained. The new approach is used to perform a parametric study analyzing the effect of refrigerant type, pipe diameter, and mass flow rate on the flow and heat transfer characteristics in evaporators.     

Heat loss characteristics study of a trapezoidal cavity absorber with and without plate for a linear Fresnel reflector solar concentrator system

The numerical and experimental studies are conducted to analyze the heat loss in the cavity absorbers of linear Fresnel reflecting solar concentrator (LFRSC). The cavity is trapezoidal shape in cross section, which is placed at focus of the concentrator, has multiple tubes and water is used as the working fluid. The upper surface of the cavity has two models; with copper plate, above which absorber tubes are placed together and without copper plate i.e. absorber tubes alone without copper plate underneath. In both the models, the heat loss coefficient of projected absorber surfaces is analyzed with and without black chrome coating. For the numerical simulation of the trapezoidal cavity absorber, ANSYS FLUENT 12.0 version is used to develop the two dimensional model with non-Boussinesq numerical approximation. For the experimental study, two cavity absorbers are designed for operating in conjunction with a LFRSC experimental set up for the area of 4.0 m². The overall heat loss coefficients are also estimated analytically by cavity correlations. The trend of variation of estimated heat loss coefficient by both methods is similar to experimental values. Also, estimated values by numerical study are very close to analytical and experimental values and the numerical model can be used for further analysis.     

散热片基板开孔对自然对流换热的影响

为研究自然对流情况下矩形散热片基板开孔对换热的影响,采用数值模拟方法对基板开孔的散热片的传热性能进行了分析,讨论了开孔后换热强化的物理机制。结果表明:开孔后发热元件的温度降低;通孔破坏了散热片基板上速度边界层的形成,从而强化了局部表面处的对流换热。     

Energetic budget on an evaporating monodisperse droplet stream using combined optical methods: Evaluation of the convective heat transfer

Aerothermal properties in a fuel spray is a central problem in the field of the design of the combustion chambers of automotive engines, turbojets or rocket engines. Heat and mass transfer models are necessary in the predictive calculation schemes used by the motorists. Reliable experimental data must be obtained for both the validation and development of new physical models linked to heat transfer and evaporation in sprays, where aerodynamic interactions have a key role. This paper proposes an experimental study of the energetic budget of a monodisperse ethanol droplet stream, injected in the thermal boundary layer of a vertical heated plate. The droplet size reduction is measured using a light scattering technique (interferential method) in order to characterize the evaporation, as the droplet mean temperature is monitored using the two colors laser-induced fluorescence technique. The convection heat transfer coefficient and the Nusselt number are inferred from the overall energetic budget, as a function of the inter-droplet distance, characterizing the interaction regime. The results are compared to physical models combined with numerical simulations available in the literature, for moving, evaporating isolated droplets and for three droplets arrangement in linear stream.     

MACROSCALE AND MICROSCALE THERMAL TRANSPORT AND THERMO-MECHANICAL INTERACTIONS: SOME NOTEWORTHY PERSPECTIVES

Some noteworthy and historical perspectives and an overview of macroscale and microscale heat transport behavior in materials and structures are presented. The topic of heat waves is also discussed. The significance of constitutive models for both macroscale and microscale heat conduction are described in conjunction with generalizations drawn concerning the physical relevance and the role of relaxation and retardation times emanating from the Jeffreys type heat flux constitutive model, with consequences to the Cattaneo heat flux model and subsequently to the Fourier heat flux model. Both macroscopic model formulations for applications to macroscopic heat conduction problems and two-step models for use in specialized applications to account for microscale heat transport mechanisms are overviewed with emphasis on the proposition of a Generalized Two-Step relaxation / retardation time-based heating model. So as to bring forth a variety of issues in a single forum, illustrative numerical applications are overviewed including some relevance to thermo-mechanical interactions     

The thermal modeling of a matrix heat exchanger using a porous medium and the thermal non-equilibrium model

Heat transfer and fluid flow characteristics through a porous medium were investigated using numerical simulations and experiment. For the numerical simulations two models were created: a two-dimensional numerical model and a Fluent™ computational fluid dynamics (CFD) porous media model. The experimental investigation consisted of a flow channel with a porous medium section that was heated from below by a heat source. The results of the numerical models were compared to the experimental data in order to determine the accuracy of the models. The numerical model was then modified to better simulate a matrix heat exchanger. This numerical model then generated temperature profiles that were used to calculate the heat transfer coefficient of the matrix heat exchanger and develop a correlation between the Nusselt number and the Reynolds number.     

Simulation of Velocity and Temperature Distributions of Displacement Ventilation System with Single or Double Heat Sources

In order to obtain a better understanding of flow characteristics of displacement ventilation,thethree-dimensional numerical models are developed using the CFD technology.The numericalsimulation results are verified by experiments,based on this,the velocity and temperature distributionof three-dimensional displacement ventilation system with single and double heat sources are studied.Velocity and temperature fields under two different cases of heat source are analyzed and compared.The numerical results show that there are three layers in vertical temperature fields of displacementventilation system with single or double heat sources,and the vertical temperature distribution ofsingle heat source is different from that of double heat sources.When indoor load is large,the comfortrequirement of people indoor can't be satisfied with displacement ventilation system only,thus anadditional refrigeration system is necessary.Furthermore,under the condition of two heat sources,thedisplacement ventilation parameters can't be computed simply according to single heat source inletparameters,therefore the interaction between heat sources should be considered.     

A NEW LOW-REYNOLDS VERSION OF AN EXPLICIT ALGEBRAIC STRESS MODEL FOR TURBULENT CONVECTIVE HEAT TRANSFER IN DUCTS

This investigation concerns performance of a new low-Reynolds version of an explicit algebraic stress model (EASM) for numerical calculation of turbulent forced-convective heat transfer and fluid flow in straight ducts with fully developed conditions. The turbulent heat fluxes are modeled by a SED concept, the GGDH, and the WET methods. New versions of GGDH, WET, and EASM are presented for low Reynolds numbers. However, at high Reynolds numbers, two wall functions are used, one for velocity fields and one for the temperature field. All the models are computed in a general three-dimensional channel. The low-Reynolds version of the models presented is very stable and has been used for Reynolds numbers up to 70,000 with least demanded number of grid points, and without any convergence problem or stability problem.