多孔介质粒径对建筑结构热质传递的影响

汲液式多孔层置于建筑结构中,通过多孔材料的主动吸水、被动蒸发产生制冷效果,减少了外界的动力消耗。应用描述非饱和多孔介质热质迁移的数学模型,在不同环境参数下,分析了床层粒径对多孔床内部非饱和场量的影响;以含湿砂石多孔床层为对象,实验研究了不同粒径床层热湿迁移环境因子特性。数值分析与实验相符合,所获的结果可为含湿多孔填料床制冷性能的开发和利用提供一定的指导。     

屋面被动冷却蒸发层温度波衰减

有含湿砂层存在的被动蒸发冷却屋面的温度波衰减，在本质上不同于干燥状态情况。该文研究了含湿砂层蒸发过程的温度波衰减，获得了含湿砂层常温工况下的蓄热系数和热惰性指标，该指标可用于含湿砂层的构造体系的衰减度计算。     

太阳能烟囱对海水蒸发强化效果的研究

针对自然水体蒸发和太阳能烟囱强化蒸发系统分别建立了理论模型和对比实验装置,考察了具体的强化效果.研究结果表明:由于集热棚和烟囱的存在,自然蒸发和强化蒸发系统的温度变化与分布不同,水温分别升高5℃以下和约15℃,多孔材料则产生相反的影响趋势;太阳能烟囱强化水分蒸发的效果是显著的,如果考虑到降雨的影响,加人多孔材料后系统的蒸发量仍最大;理论模型能较好地预测实验结果并可给出优化依据.     

被动蒸发冷却墙体换热性能的研究

采用数值模拟的方法分析由含湿多孔陶瓷管组成的被动蒸发冷却墙体(PECWs)的换热性能。研究不同排列方式对空气温度及水蒸气质量分数的影响,研究得出:在含湿多孔陶瓷管处于叉排布置情况下,流经其表面的空气温度变化和相对湿度变化较大,而且蒸发冷却效果更佳。     

多孔介质蒸发制冷板应用于建筑墙体的性能分析

把含湿多孔介质置于建筑墙体结构中,在室外环境的作用下,多孔介质外表面和内部的水分蒸发吸热,为房间提供部分冷量。文章表述将含湿多孔介质置于建筑北墙中,在建立多孔介质热湿平衡的基础上,采用描述非饱和多孔介质热质迁移的数学模型,分析了室外环境参数及多孔床层结构对床层内温度分布、蒸发量场及水蒸气迁移的影响,为多孔介质应用于建筑结构的推广和应用提供理论指导。     

太阳能被动蒸发用动态热湿气候风洞实验台研制

在传统风洞风速模拟与控制实验技术基础上,通过增加太阳辐射模拟和空气温湿度控制,初步实现对室外自然气候中太阳辐射,风速及温、湿度环境的模拟控制.经过对可视化程序设计的风洞环境测控系统的调试,风洞内4个参数(辐射照度、风速、温度和湿度)各指令值与模拟值的平均偏差分别为-0.6%、 2.9%、 0.7%和-0.7%,此风洞实验台可以用于含湿建筑材料太阳能被动蒸发降温问题的研究.     

基于GO/PI/PTFE复合薄膜的热空气吹掠型太阳能界面蒸发效率实验研究

为了提高太阳能界面蒸发的蒸发效率,从改变结构设计和光热材料两个方面出发,设计了一种热空气吹掠型太阳能界面蒸发装置。该蒸发装置利用平板型太阳能空气集热器产生的高温空气吹过蒸发表面,加速界面蒸发;同时利用氧化石墨烯的性能优势,制备了氧化石墨烯/聚酰亚胺/聚四氟乙烯膜(GO/PI/PTFE)复合薄膜作为光热材料,以提高装置蒸发效率。最后通过实验对该蒸发装置的性能进行分析验证。研究结果表明：制备得到的GO/PI/PTFE复合薄膜具有更强的光吸收能力,且亲水性能更佳。在蒸发表面吹入速度为4 m/s、温度为65℃的热空气,太阳辐照度为1000 W/m²的条件下,在1800 s时,采用GO/PI/PTFE复合薄膜但无热风吹掠的蒸发装置对应的蒸发速率为1.22 kg/(m²·h),与纯水蒸发装置相比,蒸发速率提高了3.2倍,蒸发效率提高了59.5%;热空气吹掠型太阳能界面蒸发装置的蒸发效率为88.0%,高于纯水蒸发装置和无热空气吹掠的蒸发装置,与纯水蒸发装置相比,其蒸发速率提高了5.5倍,蒸发效率提高了68.0%。热空气吹掠可以提高蒸发量,进而提高蒸发装置的...     

太阳能界面蒸发的应用综述

太阳能界面蒸发是利用特定结构将能量局限在光吸收层,使水分在结构表面完成蒸发.由于太阳能界面蒸发器装置结构简单、占地空间小、能量利用率高,且对运行环境要求低,受到研究者的广泛关注.目前,研究者们从光吸收体材料、热量管理、蒸发器结构等方面切入,对太阳能界面蒸发方法进行了丰富研究,然而太阳能界面蒸发方法在应用方面的研究相对较...     

自然环境下湿分分层土壤中热湿迁移规律的研究

建立描述存在干饱和层时的土壤热湿传递的数学模型并进行数值模拟，获得自然环境下土壤中温度、湿分分布以及水分蒸发的动态特性，分析干饱和土壤层对土壤热湿迁移及水分蒸发的影响。数值模拟获得实验支持。     

降膜蒸发—凝结型闭式循环太阳能蒸馏系统的模拟实验研究

建立了一套采光面积为1．07m∧2、主动回收蒸汽潜热及浓海不余热降膜蒸发－凝结型闭式循环太阳能蒸馏系统,4盏卤素灯作为太阳能模拟器，对该系统进行了模拟实验研究。实验结果表明，由于在本蒸馏系统中采用了强迫降膜蒸发及降膜凝结技术，使其中大部分的蒸汽潜热以及浓盐水的显热都得到了重复利用，单位采光面积的产量相对于传统的盘式（单级）太阳能蒸馏器提高了2－3倍。     

Effects of CeO2 additive on redox characteristics of Fe-based mixed oxide mediums for storage and production of hydrogen

Effects of CeO₂ additive to Fe-based mixed oxide mediums with Rh and ZrO₂ for chemical hydrogen storage were investigated in terms of stability and reactivity of the mediums in water splitting oxidation with repeated redox cycles. The mediums with CeO₂ content ranging from 0 to 30 wt% were prepared by co-precipitation method using urea solution as a precipitant. The hydrogen storage and release properties were investigated during repeated isothermal redox cycles at 823 K for reduction with hydrogen and 623 K for oxidation with water vapor under atmospheric pressure. The amount of hydrogen produced by the mediums, both with and without CeO₂, was maintained at an almost constant level over ten repeated redox cycles. However, the oxidation rates of the mediums without CeO₂ were decreased during repeated redox cycles while that increased with increasing CeO₂ contents. Especially, the mediums added with 30 wt% of CeO₂ (FRZC-30) showed high activity and stability for ten redox cycles, the degree of hydrogen storage was almost maintained ca. 1.9 wt% on the basis of total amount of the medium.     

适用于燃气STIG循环中湿燃气的状态方程

将燃煤气的ＳＴＩＧ循环中湿燃气当作实际气体处理，利用两项维里方程的 对比态形式，建立了湿燃气的状态方程，用此状态方程及余函数修正法计算了湿 燃气的热力性质，并与按理想气体计算的湿燃气的热力性质进行了比较。     

An inverse problem of parameter estimation for heat and mass transfer in capillary porous media

This work deals with the solution of an inverse problem of parameter estimation involving heat and mass transfer in capillary porous media, as described by the dimensionless linear Luikov’s equations. The physical problem under picture involves the drying of a moist porous one-dimensional medium. The main objective of this paper is to simultaneously estimate the dimensionless parameters appearing in the formulation of the physical problem by using transient temperature and moisture content measurements taken inside the medium. The inverse problem is solved by using the Levenberg-Marquardt method of minimization of the least-squares norm with simulated measurements.     

适用于宽温度和压力范围的湿空气热力性质分段计算方法

根据计算范围的不同,提出适合宽温度、压力范围,涵盖多个湿空气热物理性质参数的分段计算方法：在低温、低压范围内将湿空气看作理想混合气体,采用理想气体状态方程建立模型计算湿空气的热物理性质参数;在高温、高压范围内将湿空气看作干空气和水蒸气的实际二元混合气体,采用维里方程建立湿空气的半经验模型计算湿空气的热物理性质参数.分析确定了分段计算的分界点,并说明了分段计算的连续性.结果表明：与参考文献的计算结果相比,采用该文提出的湿空气热力性质分段方法得出的计算结果的最大误差仅为4.5%,且计算过程简单快捷,易于程序实现,可用于绘制焓湿图.     

Extension of the zonal method to inhomogeneous non-grey semi-transparent medium

A radiation model is proposed to extend the zonal method of Hottel to semi-transparent inhomogeneous real combusting gas–soot mixture in a 2-D black-walled rectangular enclosure. The direct exchange areas are carried out by direct numerical integration and then adjusted to meet the conservation constraints using two smoothing processes namely the Larsen and Howell's least squares and generalized Lawson's improved smoothing methods, which has not been previously done to the best knowledge of the authors. The predicted net radiative heat flux distributions compare favorably with benchmark solutions for two test cases dealing with isothermal and non-isothermal homogeneous mediums. It is concluded from this investigation that there is no significant effect of the smoothing method on the computed wall heat fluxes for the homogeneous and inhomogeneous test cases using different grey gases number. The grid dependence study depicts that the numerical solutions fully achieve grid independence. It is worth noting that it can be proceeded with the present extended zonal method and computer code to more complex cases. The results based on the generalized Lawson's smoothing method compare favorably with those yielded by the popular least squares method and, consequently, can be considered as a benchmark solution for other investigations.     

Three dimensional numerical modeling of simultaneous heat and moisture transfer in a moist object subjected to convective drying

The drying behavior of a moist object subjected to convective drying is analyzed numerically by solving heat and moisture transfer equations. A 3-D numerical model is developed for the prediction of transient temperature and moisture distribution in a rectangular shaped moist object during the convective drying process. The heat transfer coefficients at the surfaces of the moist object are calculated with an in-house computational fluid dynamics (CFD) code. The mass transfer coefficients are then obtained from the analogy between the thermal and concentration boundary layer. Both these transfer coefficients are used for the convective boundary conditions while solving the simultaneous heat and mass transfer governing equations for the moist object. The finite volume method (FVM) with fully implicit scheme is used for discretization of the transient heat and moisture transfer governing equations. The coupling between the CFD and simultaneous heat and moisture transfer model is assumed to be one way. The effect of velocity and temperature of the drying air on the moist object are analyzed. The optimized drying time is predicted for different air inlet velocity, temperature and moisture content. The drying rate can be increased by increasing the air flow velocity. Approximately, 40% of drying time is saved while increasing the air temperature from 313 to 353 K. The importance of the inclusion of variable surface transfer coefficients with the heat and mass transfer model is justified.     

A new approach to analysis and optimization of evaporative cooling system II: Applications

After introducing the concepts of moisture entransy, moisture entransy dissipation and thermal resistance based on moisture entransy dissipation (TRMED) in part I of this study, we further analyze several direct/indirect evaporative cooling processes based on the above concepts in this part. The nature of moisture entransy, moisture entransy dissipation and TRMED during evaporative cooling processes was reexamined. The results demonstrate that it is the moisture entransy, not the enthalpy, that represents the endothermic ability of a moist air, and reducing the entransy dissipation by both enlarging the thermal conductance of heat and mass transfer, and decreasing the temperature potential of the moist air, i.e. the difference between the dry-bulb temperature of moist air over its dew-point temperature, will result in a smaller system TRMED, and consequently a better evaporative cooling performance. Then, a minimum thermal resistance law for optimizing evaporative cooling systems is developed. For given mass flow rates of both moist air and water, with prescribed moist air and water conditions, minimizing the TRMED will actually lead to the most efficient evaporative cooling performance. Finally, the thermal conductance allocation for an indirect evaporative cooling system is optimized to illustrate the application of the proposed minimum thermal resistance law.     

直流锅炉氢氟酸化学清洗

重点介绍直流锅炉氢氟酸酸洗的目的，方法及过程，还对不同介质的化学清洗进行了比较。     

Analysis of two‐dimensional heat and moisture transfer during drying of spherical objects

This paper deals with the numerical and analytical modelling of two‐dimensional heat and moisture transfer during drying of a spherical object. Drying is considered to be a process of simultaneous heat and moisture transfer whereby moisture is vapourized by means of a drying fluid (e.g. air), as it passes over a moist object. Numerical modelling of two‐dimensional heat and moisture transfer during drying of a spherical object is carried out using an explicit finite‐difference approach. Temperature and moisture distributions inside the object are determined by using the developed computer code. Moreover, the results predicted from the present model are compared with the experimental data available in the literature and a considerably high agreement is found. Copyright © 2003 John Wiley & Sons, Ltd.     

基于神经网络的传热法测量气固两相流中固体流量的研究

利用人工神经网络优良的非线性映射能力,设计了一个3层前馈式神经网络用于传热法预测气固两相流中的固相流量,预测结果和实验结果吻合较好,为稀相气固两相流中固相流量的测量提供了一种简单、可靠的新方法。