空气隙膜蒸馏系统对流换热实验研究

空气隙膜蒸馏是一种新型的膜分离技术,可用于海水、苦咸水的淡化处理,尤其是在超纯水制备方面具有极强的竞争力.文中的空气隙膜蒸馏实验装置采用旋转切向入流的方式来强化膜蒸馏的传热传质过程,针对这种新型的入流方式,结合实验数据,给出了料液进口温度对于膜通量的影响,给出了计算空气隙膜蒸馏系统中热容腔内对流换热传热系数的经验公式.     

太阳能膜蒸馏集热系统实验研究

根据实测太阳辐射量、风向、风速等气象数据以及集热器进出口温度、水箱温度等参数的变化情况,分析了太阳能集热系统稳定高效运行的基本规律,该系统可以使用太阳能等低位热能作为驱动力,用于海水、苦咸水的淡化处理,采用的新型U型管式集热器系统作为膜蒸馏的低位热源,不仅环保、节能,而且高效。     

太阳能膜蒸馏系统建模与仿真

以太阳能为驱动力，利用高分子疏水性微孔膜提供较大的传质表面来实现水溶液气化和传质的分离过程。文章概述了太阳能膜蒸馏的技术，根据传热学及相关理论建立了数学模型，并运用LabVIEW软件对太阳能膜蒸馏系统进行了动态模拟与仿真。     

空气隙膜蒸馏产水量预测模型研究

对比分析了几种主要的膜蒸馏传质模型,发现对于实验所用孔径较大的膜,应以Poiseuille流动为主要的传质模式,不能用单一的Knudsen扩散来预测膜通量。针对现有的传质模型所需计算参数多、计算过程复杂等问题,并出于简单易算的考虑,在斯蒂芬定律的基础上引入了膜材料特性修正系数和膜变形修正系数,给出了一个适用于空气隙膜蒸馏的工程预测模型,该模型直接使用热溶液和冷却水的温度来进行计算,虽然在个别点上误差较大,但其具有方程简单、易于计算的特点,仍不失为一种较好的工程预测模型。     

新型太阳能膜蒸馏聚光系统光学性能模拟研究

利用太阳能加热膜蒸馏淡化苦咸水是一项水处理技术。通过对完整型抛物面聚光系统进行改造,建立了完整型抛物面、非完整型抛物面、同轴非完整型平移抛物面3种聚光系统的三维模型。利用蒙特卡洛光线追踪法模拟了经聚光器聚光在平板接收器表面的辐射强度分布。与其它两种聚光系统比较,同轴非完整型平移聚光系统的辐射强度峰值最小、均值相差不大,且有两条光斑,光学效率达到85.65%。针对同轴非完整型平移聚光系统,在焦距不变的条件下,模拟环数和边缘角对接收器表面辐射强度分布的影响,从而得出辐射强度随环数和边缘角的变化规律。     

太阳能膜蒸馏淡化系统试验及热性能分析

太阳能膜蒸馏淡化水是新型的水处理技术。通过太阳辐射量、水箱温度、膜通量等参数对系统运行影响的试验研究表明,即使在较寒冷的11月份,自然循环条件下水箱的温度也可维持在40℃以上,最高温度可达65℃,可以满足膜蒸馏系统运行的热源条件;在夏季,注入新水的太阳能膜蒸馏实验系统12 h的产水量为4.98kg,可为3口之家提供一天的健康饮用水。文章根据系统的热平衡条件,给出了太阳能膜蒸馏系统产水量的计算公式。     

太阳能聚光光伏-膜蒸馏海水淡化复合系统研究

提出一种可在海岛或偏远地区同时产生电力和淡水的聚光光伏-膜蒸馏海水淡化复合系统。对该系统的工作原理以及结构设计进行介绍。对系统的聚光结构进行光学仿真,研究汇聚到太阳电池上的光线接收率及能流密度的均匀性,结果表明,入射角在15°以内时,位置聚光比方差均小于0.8。在实际天气条件下对系统进行实验研究,结果表明,在夏秋季太阳辐照度为800 W/m²的条件下,系统每小时淡水产量可达375.8 g/m²,产水效率可达33.1%,每小时平均输出功率可达61.7 W/m²,电效率为8.0%,系统整体效率可达41.3%。在冬季条件下,对光伏发电功率和发电效率影响不大,但对装置的产水量有较明显的影响,但产水效率仍可达到26%以上。     

太阳能膜蒸馏海水淡化技术研究和发展状况

太阳能膜蒸馏海水淡化技术是以太阳能为驱动能源、基于膜蒸馏过程的新型海水淡化技术。介绍了太阳能膜蒸馏海水淡化技术的原理,总结并分析了国内外研究发展状况,指出了其优势所在和发展前景。     

太阳能光热-光电空气隙膜蒸馏系统实验研究

针对传统苦咸水淡化中的高能耗问题,设计太阳能光热-光电空气隙膜蒸馏耦合系统。实验研究系统运行稳定性,系统连续9、24 h运行工况下热电参数对膜通量的影响;系统获得温度和膜通量随太阳辐照度的变化,理论计算集热面积与膜面积最优匹配。研究表明:系统白天连续9 h运行最大膜通量为5.84 kg/(m~2·h),总产水量为1.80 kg,实际日产水量达43.47 kg/(m~2·h),单位产水热耗为495.3 kWh/m~3;连续24 h运行最大膜通量13.07 kg/(m~2·h),总产水量为2.99 kg,实际日产水量为71.95 kg/(m~2·d),单位淡水热耗为1095.1 kWh/m~3;系统在2种工况下均稳定运行,因此,按照系统连续9 h的产水量,需5.67 m~2的太阳集热器配备0.1248 m~2的平板膜和实际产水7.42 L/d满足3口之家6 L的日常饮用水需求。     

太阳能空气集热器研究进展

本文综合评述了各种太阳能空气集热器的研究进展。     

以空气源热泵辅助加热的太阳能热水系统

介绍了太阳能热泵热水系统的运行原理及控制方式,分析了太阳能热泵热水系统在上海某高校学生宿舍的应用情况。以每吨热水的加热成本为指标,对几种热源热水系统的经济性进行了比较,分析了太阳能热泵热水系统的节能效果。     

Mixed convection heat transfer in a passive solar building

Convective heat transfer through apertures such as doorways can be an important process by which thermal energy is transferred from one zone to another zone of a building. In this article, interzonal natural and forced convection in a two- and a three-zone, full-scale building are examined. Aperture velocity and temperature distributions are measured and the experimental interzonal mass flow rate and heat transfer are determined. A model based on zone temperature distributions is derived to predict the interzonal mass flow rate and heat transfer. The measured and predicted interzonal flow rate and heat transfer are compared and found to be in good agreement.     

Numerical study of the heat and mass transfer in inclined glazing cavity: Application to a solar distillation cell

A numerical analysis is performed for the natural convection flow resulting from the combined buoyancy effects of thermal and mass diffusion in an inclined cavity. This work enters within the framework of general study dealing with the mathematical model for solar brackish water desalination unit. The problem is stated in a Cartesian coordinates system, involves the use of a control volume-based finite-element method and solves the full vorticity transport equation together with the stream function, concentration and energy equations. The predicted stream function patterns, isoconcentration and isotherms are presented for different thermal Rayleigh numbers. The heat and mass transfer evolution are explained in terms of dynamic and temperature fields of the flow in the inclined cavity. In particular, the desirable flow for enhancing the performance of the solar distiller is determined by examining flow patterns.     

辐射侧加热腔内自然对流传热特性研究

为了明确辐射侧加热封闭方腔内半透明流体的自然对流传热现象及规律,采用有限体积法进行数值模拟研究,分析了瑞利数和光学厚度对流场、温度场以及传热特性的影响。结果表明：与传统侧壁加热腔内自然对流相比,辐射侧加热腔内等温线和流场分布规律不一致;随着瑞利数和光学厚度增加,涡心由中心位置沿直线向辐射入射侧斜上方偏移;随着瑞利数增加,等温线变得更均匀;随着光学厚度增加,等温线变密,努塞尔数Nu与瑞利数RaT的标度律指数减小,当光学厚度增加到一定时标度律不再变化,此时传热标度律与传统恒壁温侧加热腔内自然对流相当,满足Nu~Ra0.29T。     

Natural convection heat transfer of water in a horizontal circular gap

An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data points were correlated using Rayleigh versus Nusselt number in various forms, based on different independent variables. The effects of different characteristic lengths and film temperatures were discussed. The results show that the buoyancy force acts as a resistance force for natural convection heat transfer on a downward facing horizontal heated surface in a confined space. For the estimation of the natural convection heat transfer under the present conditions, empirical correlations in which Nusselt number is expressed as a function of the Rayleigh number, or both Rayleigh and Prandtl numbers, may be used. When it is accurately predicted, the Nusselt number is expressed as a function of the Rayleigh and Prandtl numbers, as well as the gap width-to-heated surface diameter ratio; and uses the temperature difference between the heated surface and the ambient fluid in the definition of Rayleigh number. The characteristic length is the gap size and the film temperature is the average fluid temperature.     

Modeling the free convection heat transfer in a partitioned cavity using ANFIS

In this paper, an adaptive neuro-fuzzy inference system (ANFIS) is used to predict the free convection in a partitioned cavity consisting of an adiabatic partition. The main focus of the present paper is to consider the effects of partition angle and Rayleigh number variation on average heat transfer in the partitioned cavity. The training data for optimizing the ANFIS structure is obtained experimentally. For the best ANFIS structure obtained in this study, the mean relative errors of the train and test data were found to be 0.055% and 1.735% respectively, which shows that ANFIS can predict the experimental results precisely.     

太阳能热水系统用热管性能要求及功率测试方法

阐述了热管传热性能的重要参数——等温性和传输功率的测试方法。规定了热管测试中,蒸发段、绝热段和冷凝段的长度、循环水流量以及进出口的温度差等参数的要求及控制方法。提出了一般的热管质量控制方案。