NUMERICAL INVESTIGATION OF MASS AND HEAT TRANSFER IN SODIUM POOL COMBUSTION

Liquid sodium pool combustion is a coupled phenomenon of heat and mass transfer, chemical reaction, and aerosol dynamics. This article presents numerical investigation of the coupled phenomena using a new computational tool. Boundary layer equations are solved to obtain the thermalhydraulic field above the pool surface. The chemical reaction and heat and mass transfer are solved interactively considering radiation heat transfer and behavior of reaction product aerosols. Numerical results are compared with experiments, and agreement is excellent concerning burning rate, flame temperature, and height. It is concluded that the sodium pool combustion is self-limited and negative feedback is at work.     

开式吸收式热泵降膜吸收器热质传输研究

针对开式循环吸收式热泵系统中的吸收器,建立了竖直管降膜式吸收器模型,分析了吸收器内部的热质传输规律,并将拟合的传质系数与实验结果进行了比较.计算结果表明,溶液浓度升高最利于水蒸汽吸收,溶液温度升高有利于热的回收利用,增大降膜管径及增加降膜管长度均利于吸收过程的进行.计算结果可为此类吸收器的设计提供参考.     

叉流高效降膜蒸发器传热传质规律研究

建立了描述叉流式和膜蒸发过程的理论模型,预测结果与实验基本相符,在分析和探讨蒸发器传热传质规律过程中,发现根据入口水温的不同,蒸发器可分别用于蒸发冷却和海水淡化,从蒸发冷却和加热蒸发两个角度讨论了气流,水流及蒸发器结构参数对系统性能的影响,为蒸发器的优化设计奠定了基础。     

多孔介质对太阳池传热传质影响的研究

通过实验与数值模拟相结合的方法研究在太阳池底部增设多孔介质水层对太阳池热盐双扩散及储热量、稳定性等的影响.在实验室研究了多孔介质对盐扩散的抑制作用.在海边沙滩建造了两个小型太阳池,测量了有无多孔介质太阳池的温度分布和盐度分布并进行数值模拟,模拟值与实验值吻合较好.计算了有无多孔介质太阳池盐梯度的分布、池子稳定性情况以及多孔介质对太阳池的储热量的影响.结果表明,在太阳池底部加设多孔介质水层可以提高太阳池LCZ温度.多孔介质水层有利于提高太阳池的储热量,有利于抑制盐分向上扩散,可以节省太阳池的盐资源消耗,并有利于提高非对流层的盐梯度和稳定性.     

吸附式制冷系统传热传质过程的数值模拟

建立了沸石－水吸附式制冷系统吸附床在非第一类边界条件时的二维传热传质模型。考虑了工质对的吸附特性对脱附过程的影响,讨论了肋片数量、肋片物性参数,吸附床的有效导热系数,接触热阻等参数对脱附时间的影响。结果表明,增加肋片可以改善吸附床的性能,其中肋片的数量和接触热阻的影响较大,肋片的物性参数影响不大。     

抛物跟踪式太阳高温集热器的研究

对单轴跟踪太阳聚集系统（ＰＴＣ）进行了光学分析。对集热管内流体的混合对流（强迫对流加自然对流）和传热过程进行了探讨。理论模拟结果与实验结果吻合较好,两者间的最大偏差小于８％。     

STOCHASTIC FINITE-ELEMENT ANALYSIS OF COUPLED HEAT AND MASS TRANSFER PROBLEMS WITH RANDOM FIELD PARAMETERS

A first-order perturbation algorithm for the computation of mean values and variances of transient temperature and moisture fields during coupled heat and mass transfer problems with random field parameters has been developed and implemented. The algorithm is based on the Galerkin finite-element discretization of Luikov's heat and mass transfer equations for capillary porous bodies and is computationally less demanding than the Monte Carlo method. The algorithm has been programmed in MATLAB and applied to a published test case of a drying process for soybean kernels. The simulations indicate that the stochastic fluctuations of the thermophysical properties and the process conditions may cause a considerable level of uncertainty in the predicted temperatures and moisture contents inside the product.     

MODELING SIMULTANEOUS HEAT AND MASS TRANSFER USING THE CONTROL-VOLUME METHOD

A control-volume formulation for the solution of a set of two-way coupled heat and diffusive moisture transfer equations is presented in three dimensions. The three-dimensional model in Cartesian coordinates was extended to other geometries using an equivalent surface area-to-volume ratio index. The solution procedure developed uses a fully implicit time-stepping scheme for the solution of the coupled set of equations to study the drying behavior of barley and starch food. Simulated results of the one-way and the two-way coupled equations were compared with the finite-element analysis (two-way coupled and three-way coupled equation set) and experimental results from the literature. Among the products tested, the maximum deviations between experimental and simulation results were 5.0°C in temperature for barley drying, and 0.2 % moisture for starch drying. The overall predictions agreed well with the available experimental data and show good potential for application in grain and food drying.     

采用床内强制对流进行传热传质的固体吸附式循环分析

采用一维两温度模型，以活性炭纤维－氨为工质对，模拟计算了对流热波循环的吸附床加热过程和冷却过程中床内的温度分布和变化趋势，并分析计算了对流热波循环的性能参数。系统的回热率达０．４，热泵效率达１．７８，热泵系统的能量密度为１６１６Ｗ／ｋｇ。对系统加以优化，可获得更高的回热率和ＣＯＰ。     

竖直埋管地热换热器钻孔内的传热分析

准三维模型为竖直埋管地热换热器的结构优化提供了较为精确的理论基础。利用准三维模型对竖直埋管地热换热器进行分析与研究得出，不同的行程布置对双U型埋管地热换热器的传热性能有较大影响。就钻孔内热阻的对比，双U型埋管比单U型埋管钻孔内的热阻低，因而双U型埋管地热换热器较单U型埋管地热换热器更为合理。     

太阳能蒸馏器中一组传热传质关系式

建立了盘式太阳能蒸馏器中一组传热传质关系式,并用多级迭盘式蒸馏室进行稳态模拟实验。发现该关系式在较大的雷利数范围及较宽的温度段内能很好地预示蒸馏器的产水量。     

太阳能蒸馏器非稳态传热传质问题的研究

建立了太阳能蒸馏器的非稳态物理数学模型,对其进行了传热、传质问题的研究,分析结果与试验结果吻合较好。结果表明:海水蒸发是海水温度和△T共同作用的结果。温度差是驱动海水蒸发的动力,水温对水表面蒸发有重要影响。在任何温度下,表面蒸发都可进行,但对蒸馏器来说,只有水温超过40℃,且△T为正值时,才有显著的蒸发,收到可观的淡水。高峰产水区主要在下午与傍晚时段,此时段占整个昼夜的比例不大,但是其对日产水量的贡献却是主要的。随着海水深度的增加,瞬时产水量白天减少,晚上增加,日产水量减少;当水深大于10cm时,日产水量变化不大;随着环境风速的增加,瞬时产水量白天增加,晚上减少,风速对日产水量的影响很小,但强风使日产水量有所下降。     

FINITE ELEMENT ANALYSIS OF COUPLED HEAT. MASS,AND PRESSURE TRANSFER IN POROUS BIOMATERIALS

Abstract

The finite element method was used to solve Luikov's system of partial differential equations for neat, mass, and pressure transfer in capillary porous bodies. The finite element predictions were validated by comparing with exact solutions and the analytical results given by Mikhailov and Shishedjiev [1]. An application of the finite element method to the drying of wood (spruce) and a comparison based on an eigenvalue solution for simultaneous heat and mass transfer [2] are also provided. This technique was applied to study the coupled transport process in a silicon gel. The simulation indicated that the results obtained from the heat, mass, and pressure transfer model showed a marked difference from the results obtained by the heat and mass transfer model.     

围护结构热质耦合传递实验研究

对单层围护结构热质耦合传递过程进行了实验研究。在建立围护结构墙体时,预留一块围护结构用炉渣混凝土砌块测量其孔隙率,初始体积含湿量,干、湿状态的导热系数以及完全干燥状态的密度,并计算砌块固体骨架的导热系数。实验测量321d,该文对实验结果进行了分析,分析结果表明:随着边界条件的变化,围护结构表面及内部温度能够很快达到平衡;但由于湿扩散速度比热传递速度慢得多,因此只有围护结构内外表面的相对湿度受边界条件影响,围护结构中间的相对湿度稳定并持续很高。     

内冷型溶液除湿器的热质交换分析及流型比较研究

建立了分析传热传质的数学模型,并采用了文献中的实验数据进行验证,模型的计算值和文献中实验结果的偏差在±10%以内.藉此模型进行计算分析,得出内冷型除湿器的除湿量随着空气进口含湿量、溶液进口浓度、空气与溶液的传质单元数NTUa、溶液与冷水的传热单元数NTUw的增加而增大,随着冷水进口温度的增加而降低.针对文献中的空气与溶液逆流、冷水与溶液叉流的流型1和空气与溶液顺流、冷水与溶液逆流的流型2进行比较分析,得出相同情况下流型1的除湿性能总优于流型2,且两种流型的除湿量的差别随,NTUa的增加而增大.     

SOLUTION OF THE INVERSE PROBLEMS IN HEAT TRANSFER AND THERMAL STRESS ANALYSIS

The stable method of soloing inverse problems in heat transfer and inverse problems concerning thermal stress control in elements of complex shapes is presented. Based on the discrete form of Duhamel's integral and on so-called future time steps, a simple and accurate method of solving one- and multi-dimensional inverse problems is developed. Two examples illustrating the application of the described method are presented.     

U型管埋地换热器三维传热模型及实验对比分析

针对U型管埋地换热器的传热特点,考虑了两管脚之间的相互影响,建立起非稳态传热模型。采用数值解法对该理论模型进行了求解,并将结果与实验值进行了对比分析,发现两者变化趋势一致,但理论计算结果比实验测试值低,其中的一个重要原因是因为换热器与土壤间的热交换不是纯导热过程,还应该进一步考虑土壤中热湿迁移等因素的影响。     

纤维复合相变材料传热模型及性能分析

该文利用所建立的纤维复合相变材料相变问题的焓法求解模型，对影响人口传热单元的传热特性的各参数进行了分析，为进行纤维复合相变材料的优化设计提供了参考。