溶液除湿/再生过程中场均匀分布原则的探讨

通过分析溶液除湿、再生过程中传热作用与传质作用的相互影响关系,得出:传质驱动力(湿差)和全热换热驱动力(焓差)的变化规律并不一致.传质驱动力场分布越均匀,传质效果越优.除湿过程和以热溶液为热源的再生过程中,传质方向与全热换热方向相同,相同条件下逆流流型的传质效果最优、叉流次之、顺流最差.而以热空气为热源的再生过程中,传质方向与全热换热方向相反,相同条件下顺流流型的传质效果最优、逆流最差.     

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.     

溴化锂溶液除湿系统再生过程实验研究

溶液除湿技术是解决空调热湿解耦控制以及将废热与太阳能引入空调的有效途径.溶液再生则是溶液除湿的一个关键过程.设计了一套溴化锂溶液再生实验装置,对溶液流量、进口溶液温度、空气流量、进口空气温度、进口空气相对湿度对系统的再生性能进行了实验研究.结果表明:对于一定结构参数和进出口溶液、空气参数的再生装置,溶液流量存在一个最佳...     

波纹板强化换热装置中带水膜饱和烟气对流传热的实验研究

为了探讨糖厂的烟气水膜除尘耦合换热技术实施的可行性,建立了带水膜湿烟气与空气之间的换热实验装置,进行带水膜湿烟气的对流传热实验研究。在该换热装置中,烟气在矩形通道中流动并喷入雾化热水,通过换热面加热另一侧的空气,同时,在烟气侧通道安装波纹板强化单元,以强化热质传递。实验确定最佳液气比,通过改变波纹板峰高、波纹段高、段数及烟气流速,研究带水膜饱和烟气的对流传热系数。结果表明:饱和烟气对空气的换热量显著;最佳液气比为3.3~4.2 L/m~3;烟气流速和波纹板添加段数的增加显著增大对流传热系数。回归了最佳液气比下的传热准则关联式。     

太阳能平板降膜型再生器的模拟和实验研究

在对液体再生机理研究的基础上,针对对流和辐射传热边界条件,建立了太阳能平板集热型再生器中逆流降膜再生过程的数学模型,并通过实验方法对该模型进行验证,实验采用CaCl2水溶液作为除湿剂,分析了各种进口参数对再生效果的影响.结果表明:模拟结果与实验数据能够较好地吻合;太阳辐射强度、空气温度、空气含湿量和溶液浓度等均对再生过程有不同程度的影响.     

开式逆流能源塔传热传质特性分析

以开式逆流能源塔为研究对象,建立开式逆流能源塔传热传质数学模型,并运用Matlab软件对数学模型进行求解。通过对开式逆流能源塔热泵实际冬季工况的测试,对数学模型的正确性进行验证。并运用所建立的数学模型对能源塔冬季传热传质的特性进行分析,得出提高能源塔空气进口干球温度和含湿量,降低载冷剂进口温度,能够增加能源塔换热量的结论。     

余热制冷装置中氨吸收器热、质耦合数值研究

船用柴油机废热品位较高,基本满足吸收式制冷装置的需要。作为吸收式制冷装置中重要的部件,吸收器的合理设计直接决定了制冷系统的综合性能。在对水平管氨降膜吸收器中传质与传热的相互关系进行详细分析的基础上,建立了完全基于热、质耦合传递的二维模型。数值计算结果表明,在氨降膜吸收过程中,强烈的传质过程是实质,起着主导作用,而传热过程仪是传质过程的外在表现。     

两种除湿溶液的再生性能对比实验研究

该文旨在比较LiBr和LiCl溶液的再生传热传质性能。通过搭建的溶液再生实验台,分别采用LiBr和LiCl溶液实验测试了一系列在溶液调湿空调的再生器中常见的工况;整理再生实验数据,针对评价传热传质性能的指标——再生量,拟和了经验公式,通过经验公式可以计算出实验范围内任意工况下的传热传质性能;再生量是衡量传热传质性能的最直观指标,进口参数等效时,LiBr和LiCl溶液的再生量差别很小,在进口溶液浓度较低(LiBr溶液在40%～43%)时,LiCl溶液的再生量较高;而进口溶液浓度较高(LiBr溶液在48%～50%)时,LiBr溶液的再生量略高。     

固着液滴蒸发研究进展及展望

固着液滴是指附着于壁面上的液滴,其蒸发行为及传热传质特性是喷雾冷却、喷墨打印等相变传热传质领域的基础问题之一。文中重点针对固着液滴蒸发过程所涉及的自身形态演变规律、气液固三相耦合传热/传质/流动特性进行了综述。结合毫微尺度固着液滴基本蒸发模式、热质传递形式、气液两相流动特征和界面输运行为,分析了液滴性质、壁面条件、气相环境条件等关键因素对固着液滴蒸发过程的内在作用机制和影响规律,提出了微纳尺度固着液滴（群）热质传递过程与机理的相关研究展望。     

可呼吸墙体热质耦合传递研究及数值模拟

可呼吸墙体中不仅有热传递,还伴随着湿传递及空气渗透,并且3个过程互相影响,协同作用。在分析国内外相关资料的基础上,采用热力学方法,并根据多孔介质中多相流体流动描述的体积平均方程,建立了热、湿和空气耦合作用下的可呼吸墙体热质传递模型。推导出热、湿和空气耦合传递等效扩散方程;找到可呼吸墙体热、湿及空气耦合作用下热质传递过程的主要影响因素湿容量Lθ、气压pG和温度T;根据等效扩散方程,通过TDM A算法,可以求得可呼吸墙体内的湿容量分布、气压分布和温度分布,并进行了数值模拟。     

Coupled heat and mass transfer characteristic in packed bed dehumidifier/regenerator using liquid desiccant

The dehumidifier and regenerator are two key components in liquid desiccant air conditioning systems. The heat transfer driving force and the mass transfer driving force influence each other, the air and desiccant outlet temperatures or humidity ratio may exceed the air and desiccant inlet parameters in the dehumidifier/regenerator. The uncoupled heat and mass transfer driving forces, enthalpy difference and relative humidity difference between the air and desiccant are derived based on the available heat and mass transfer model and validated by the experimental and numerical results. The air outlet parameter reachable region is composed of the air inlet isenthalpic line, the desiccant inlet equivalent relative humidity line and the linkage of the air and desiccant inlet statuses. Except the mass flow rate ratio and the heat and mass transfer coefficients, the air and desiccant inlet statuses and flow pattern have great effects on the dehumidifier/regenerator performance. The counter flow configuration expresses the best mass transfer performance in the dehumidifier and the hot desiccant driven regenerator, while the parallel flow configuration performs best in the hot air driven regenerator.     

溶液全热回收装置及其优化分析

分析了制约现有溶液全热回收装置效率的主要因素,以内部驱动势分布均匀一致为原则,对溶液全热回收装置进行了优化分析,并给出了在不增加装置体积投入的前提下,提高热回收装置效率的有效措施。构建了溶液全热回收装置最高可达效率的处理流程,并分析实际装置接近可达效率的程度。     

Analytical solution of combined heat and mass transfer performance in a cross-flow packed bed liquid desiccant air dehumidifier

Heat and mass transfer between air and liquid desiccant in a cross-flow packed bed dehumidifier is investigated. Analytical solutions of air and desiccant parameters as well as enthalpy and moisture efficiencies are given in the present study, based on the analogy between the combined heat and mass transfer process in the cross-flow dehumidifier and the heat transfer process in the cross-flow heat exchanger. The results given by the analytical solution are compared with numerical solutions and experimental findings. Good agreement is shown between the analytical solutions and the numerical or experimental results. The analytical solutions can be used in the optimization of the cross-flow dehumidifier.     

Heat and mass transfer in a countercurrent moving bed dryer

The objective of this work is to study the heat and mass transfer between air and soybean seeds in a countercurrent moving bed dryer, based on the application of a two-phase model to the drying process. The numerical solution of the model is obtained by using a computational code based on BDF methods (Backwards Differentials Formulas). The experimental data of air humidity and temperature and of seed moisture content and temperature at the dryer outlet are compared to the simulated values, showing a good agreement.     

Simultaneous heat and moisture transfer through a composite supported liquid membrane

Composite supported liquid membranes (SLM) are an efficient transfer media to recover heat and moisture from exhaust air due to the high moisture diffusivity in the liquid layer. However, heat transfer has adverse effects on moisture transfer since the water concentration in the LiCl solution decreases at higher temperatures. This study gives a detailed quantitative analysis of these effects. More specifically, simultaneous heat and moisture transfer through a composite supported liquid membrane is modeled. The SLM involved comprises three layers: two hydrophobic porous skin layers and a hydrophilic porous support layer where a layer of LiCl liquid solution is immobilized in the macro and micro pores as the permselective substance. The equations governing the heat mass transport in the microstructures, as well as the transfer of heat and moisture in the air streams adjacent to the membrane, are solved numerically in a coupled way. An experiment has been built to validate the model. The results found that though heat transfer has adverse effects on moisture transfer, in general, the effects on moisture effectiveness are quite limited. The high moisture permeation rates of SLM can be sustained when there is concomitant simultaneous heat transfer.     

Investigation of heat and moisture migration in unsaturated soil under natural boundary conditions

Theoretical and experimental investigations were conducted to determine the heat and moisture migration in unsaturated soil under natural surface boundary conditions. Theoretically, a new model of heat and moisture migration in unsaturated porous media was developed, in which the gradients of volume water content, temperature, and partial vapor pressure were considered as the main driving forces which influence the process of heat and moisture migration in unsaturated soil. A set of coupled, nonlinear, partial differential equations were developed, which are related dynamically to the surface boundary conditions. Heat and moisture migration in sandy soil under solar radiation and air convection were studied experimentally. Temperature, volume water content, and water table evaporation were measured under unsteady conditions. The predictions are in good agreement with experimental data from a fairly sandy soil. © 1999 Scripta Technica, Heat Trans Asian Res, 28(1): 3–17, 1999     

Experimental and Numerical Study on Heat and Mass Transfer of Cross-Flow Liquid Desiccant Dehumidifier/Regenerator

Abstract

A liquid desiccant air dehumidification system driven by heat pump was established. The performance of cross-flow dehumidifier/regenerator was experimentally investigated. The empirical correlations of Sherwood number for dehumidification/regeneration were obtained by fitting the experimental data. On the basis of the empirical correlations of Sherwood number and thermodynamics analysis of heat and mass transfer process for dehumidifier/regenerator, a cross-flow heat and mass transfer model was established. The effects of air and solution parameters on the dehumidification/regeneration performance were analyzed. The number of mass transfer units and the height-to-length ratio of the packing module were also studied. The results show that there exist optimal number of mass transfer units and height-to-length ratio in the dehumidifier/regenerator.     

大气对流对土壤内热湿迁移影响的实验研究

对土壤内热湿迁移过程进行了研究,通过对土壤内热湿迁移机理分析,根据质量守恒和能量守恒原理,建立了土壤非饱和区热湿迁移的理论模型,对大气对流环境条件下砂土内热湿迁移过程进行了实验研究,实验测量和数值计算,获得了不同大对流速度作用下土壤中温度,含水率分布以及水分蒸发强度的变化。