气凝胶玻璃系统动态传热模型及能耗性能研究

研究纳米气凝胶玻璃对太阳辐射的透过、吸收特性,考虑室外太阳入射角变化和气凝胶材料吸收太阳辐射引起温度变化的影响,建立动态状态空间传热模型和太阳辐射传递模型,并实验验证模型的准确性。模拟分析该气凝胶玻璃在长沙地区的节能潜力,结果表明与中空玻璃对比,通过气凝胶玻璃的传热得热增加,太阳辐射得热减少,夏季气凝胶玻璃引起的总得热量比中空玻璃减少约20%,冬季通过中空玻璃的室内得热量比气凝胶玻璃低61%。     

透过玻璃窗的室内太阳辐射得热量测试研究

搭建了室外太阳辐射得热最的测量装置,通过测量电加热量、风机功率,计算风机盘管换热量、围护结构传热量得到室内太阳辐射得热量.测试结果表明:室内太阳辐射得热量和实际情况一致,并且当太阳辐射强度有波动时,装置也能很好的跟踪测量透过玻璃的室内太阳辐射得热量.依据太阳辐射理论及当地地理气象条件进行数值模拟,将测试值与模拟值进行比较,两者吻合度很好.     

基于聚光集热和脉动风压的定日镜群模拟研究

太阳辐射量和风荷载会直接影响光热电站的持续发电量。文章根据新疆哈密地区中电淖毛湖光热电站的实际环境情况,建立定日镜群的三维数值模型,对不同季节太阳辐射和迎风仰角下镜群的受热情况及流场特性开展数值模拟,分析获得风在不同入射角下镜面耀斑分布情况和脉动风压系数。结果表明：模拟所得镜群阻力系数和升力系数与相关研究结果较为吻合,验证了所建模型的有效性;不同季节下耀斑的分布规律较为相似,主要取决于太阳方向角的变化;随着风入射角的增大,镜群的尾流区域呈先减小后增大趋势;由于定日镜镜群中的尾流可有效抑制风压,结合镜群的排布方式保证内部的稳定性,其中,正五边形定日镜的中心处保持较低的脉动风压,极大提高了镜面受力均衡性。     

菲涅尔聚光PV/T系统热电输出特性分析

基于螺旋式微通道冷却的菲涅尔聚光PV/T系统性能进行研究,分析太阳直射辐照度(DNI,G)、冷却水流速及入射角对其热电性能的影响。结果表明,增大冷却水流速可提高PV/T系统的光电转换效率,但当流速大于某一值后,系统光电转换效率基本保持不变;光热转换效率随流速的增大呈先增后减的趋势,且随着G的增大光热转换效率逐渐升高,当G为1000 W/m~2,冷却水流速为3.8 m/s时,系统光热转换效率可达43%;当G在200~1000 W/m~2范围时,光电光热综合效率最大值为79.55%,DNI对其影响较小;入射角的增大对系统能量转化与利用均产生不利影响,为保证系统高效运行入射角应控制在0.3°以内;同时,对菲涅尔聚光PV/T系统的输出性能进行试验测试,结果表明,呼和浩特冬季一日内,系统峰值功率13.89 W出现在G最大时,但光电转换效率最大值26%出现在G突降时刻。     

基于㶲损失分析的太阳能喷射制冷系统性能研究

利用?分析法对太阳能喷射制冷系统?损失随太阳辐射值的变化情况进行分析,了解系统各部件的?损失情况,给出系统总?损失随太阳辐射值变化的规律和系统各部件?损失占系统总?损失的比例随太阳辐射值变化的规律。结果表明:集热器?损失占系统总?损失的比例最大且随太阳辐射值的增加而减小,在太阳辐射值为500～1 100 W/m~2时,集热器?损失占系统总?损失的比例为79.28%～81.94%,因此提高集热器效率对降低系统?损失有着至关重要的影响。另外,由于喷射器固有结构的限制,随着发生温度的升高,喷射系数EER、系统性能系数COP并非一直增大,系统存在一个最佳的发生温度;控制发生温度在75℃时,随着太阳辐射值的增大,系统性能系数COP逐渐增大,在太阳辐射值达到600 W/m~2时逐渐变小。     

储热式真空管集热器入射角修正系数的研究

在实验测定吸热板表面相对太阳辐射度和涂层太阳吸收比的基础上,分析研究了圆柱形吸热体具有圆形和半圆形吸收涂层的真空管集热器,在不同管中心距下的入射角修正系数随光线入射角变化的规律。指出对于真空管集热器而言,其入射角修正系数同时取决于入射角度和入射方位角,并给出入射角修正系数的解析式,为进一步研究全日入射角修正系数提供依据。     

太阳能CO2热泵联合采暖运行特性研究

介绍一套以太阳能为主,CO2热泵机组为辅助热源的采暖系统。通过建立系统的数学模型,并对一套实际系统的现场测试,验证模型的可靠性。同时,分析太阳集热器面积对CO2热泵机组运行特性的影响。结果表明,在夜间无太阳辐射时,CO2热泵机组的功耗、制热量不随集热器面积的增加而变化;随着日间太阳辐射逐渐变大,功耗、制热量开始逐渐减少;对比集热面积为360m2和0m2时机组的制热系数,在太阳辐射最大的13∶00时,CO2热泵机组的COP提高了26.7%;一天平均提高17.3%;且系统的整体效率随集热器面积的增大也逐渐变大。     

扰流板式太阳墙内部流动传热分析

为了减少太阳墙的换热损失,提高其集热效率,文章提出了一种扰流板式太阳墙,并对普通太阳墙和扰流板式太阳墙进行数值模拟。研究结果表明:典型工况下,扰流板式太阳墙的平均集热效率和平均出风温度分别比普通太阳墙高30.03%,10.1℃;当太阳辐射强度由200 W/m~2逐渐升高至800 W/m~2时,两种太阳墙的出风温度、集热效率和热损失系数均呈现出逐渐增加的变化趋势,但总体来讲,太阳辐射强度对集热效率影响较小,对出风温度和热损失系数影响较大;当送风量发生变化时,若保证室内的最低送风温度为30℃,则扰流板式太阳墙的集热效率比普通太阳墙高32.59%,扰流板式太阳墙的热损失系数比普通太阳墙低0.94 W/(m~2·℃)。     

基于模拟光源的遮阳窗口系统太阳得热系数测试研究

为精确测量各种遮阳窗口系统的太阳得热系数,搭建一套遮阳窗口系统太阳得热系数测定实验平台。该平台主要由太阳辐射模拟器、环境室、热箱、试件、热计量箱、循环水温度控制及计量系统等组成。实验测试基于稳定传热原理测量2个恒温箱之间建筑围护的净热流值,平台对温度、流量、太阳辐射强度等热物理参数实时监控,能实现系统工况参数的自动检测、监控与存储,从而实现智能控制。接着,重点分析实验测试所需的3个标定测试以及测试方法。最后对典型试件进行测试,并与Windows 7.4的计算值进行对比,研究结果表明测试数据与计算数据具有较好的一致性,测试平台的可靠性较高。     

带平面反射板的真空集热管表面能流分布

采用几何解析的方法,对带平面反射板的真空集热管的圆周方向能流分布进行分析.根据太阳辐射晴天模型计算理论太阳辐射值,运用MatLab编程计算得出上海地区的常规安装条件下,在不同入射角时真空集热管的能流分布.通过结果分析可知,接收太阳能的主要时间段是8:40-15:20.集热管的管间距对太阳能得热有较为明显的影响,一般1.5～2.0倍管外径较为合适.尽管平面反射板使真空集热管的得热量增大15%～36%,但是否会增强真空集热管的换热效果还有待通过模拟和实验进行证实.     

Reversible low solar heat gain windows for energy savings

Summer cooling loads in buildings can be reduced with windows of low solar heat gain coefficients (SHGC). Such windows are often double glazed with the exterior pane tinted or selectively absorbing. They reject part of the absorbed solar radiation to the environment, reducing the solar heat gain. This effect is undesirable in the cold season. However, the same window installed in reverse, i.e. turned by 180°, has a significantly higher SHGC. Thus, windows that can be reversed according to the season will both reduce summer heat gains and collect much of the beneficial solar radiation in winter. This paper investigates the energy savings achievable by reversing equator-facing windows for the duration of the cold season as opposed to leaving them in the “summer position”. Candidate climates in which these savings may be significant are identified. By means of a computer simulation, seasonal energy savings are predicted for a model room with reversible, low SHGC, windows. The results indicate that for suitable climates, significant savings are achievable.     

附着液滴的玻璃层太阳辐射传递模型

针对液滴和玻璃层的太阳辐射传递特点,提出附着液滴玻璃层的太阳辐射传递模型。将入射的太阳辐射进行直散分离,基于蒙特卡洛射线追踪法对直射辐射光学性能进行计算,同时将入射角进行离散,分别在各角度范围内采用蒙特卡洛射线追踪法的直射辐射原理计算散射辐射光学性能。为了对模型进行验证,通过实验测试液滴覆盖率和太阳入射角对附着液滴玻璃层光学性能的影响,并与模型计算结果进行比较。结果表明：实验结果与计算结果差别较小,总透过率最大误差仅约为0.05,模型的准确性较高。附着液滴的玻璃层能有效降低太阳辐射透过率,且太阳辐射透过率随液滴覆盖率的增大而减小,随入射角的增大而减小。     

Optical performance of vertical axis three azimuth angles tracked solar panels

In this work, a new sun-tracking concept was proposed, and the optical performance of solar panels with such sun-tracking system was theoretically investigated based on the developed mathematical method and monthly horizontal radiation. The mechanism of the proposed sun-tracking technique is that the azimuth angle of solar panels is daily adjusted three times at three fixed positions: eastward, southward and westward in the morning, noon, and afternoon, respectively, by rotating solar panels about the vertical axis (3A sun-tracking, in short). The analysis indicated that the tilt-angle of solar panels, β_3A, azimuth angle of solar panels in the morning and afternoon from due south, ?_a, and solar hour angle when the azimuth angle adjustment was made in the morning and afternoon, ω_a, were three key parameters affecting the optical performance of such tracked solar panels. Calculation results showed that, for 3A tracked solar panels with a yearly fixed tilt-angle, the maximum annual collectible radiation was above 92% of that on a solar panel with full 2-axis sun-tracking; whereas for those with the tilt-angle being seasonally adjusted, it was above 95%. Results also showed that yearly or seasonally optimal values of β_3A, ?_a and ω_a for maximizing annual solar gain were related to site latitudes, and empirical correlations for a quick estimation of optimal values of these parameters were proposed based on climatic data of 32 sites in China.     

Off-axis aberration correction surface in solar energy application

A new fixed aberration correction surface for applications in solar energy is proposed. The surface equation was derived based on the theory of focusing heliostat and the technique of canting the mirror array at a particular incident angle. The performance of the optimized new surface is simulated and compared with that of a spherical surface for two different ranges of incident angles, i.e., 0°–33° and 33°–57°. The comparison result shows that there are considerable improvements: not only is the size and concentration of the sun’s image improved, but it is also possible to shift the hot spot from noon time to early morning and late afternoon.     

Optimization of building window system in Asian regions by analyzing solar heat gain and daylighting elements

This paper presents and optimizes the annual heating, cooling and lighting energy consumption associated with applying different types and properties of window systems in a building envelope. Through using building simulation modeling, various window properties such as U-value, solar heat gain coefficient (SHGC), and visible transmittance (Tvis) are evaluated with different window wall ratios (WWRs) and orientations in five typical Asian climates: Manila, Taipei, Shanghai, Seoul and Sapporo. By means of a regression analysis, simple charts for the relationship between window properties and building energy performance are presented as a function of U-value, SHGC, Tvis, WWR, solar aperture, effective aperture, and orientation. As a design guideline in selecting energy saving windows, an optimized window system for each climate is plotted in detailed charts and tables.     

Design guidelines for a glazing with a seasonally dependent solar transmittance

The basic design guidelines for a window and facade glass which rejects direct solar radiation during the summer period and which transmits direct solar radiation during the remainder of the year are derived. The design employs purely passive control means and is based on the seasonal change of the incident angle of solar rays and on the capability of glass prisms to refract and totally reflect or transmit solar rays dependent on the relevant incident angle. Two new design elements essentially extend the applicability of the glass in accordance with window orientation and season of direct solar light rejection.     

Solar energy availability in greenhouses as affected by condensation on cladding materials

To investigate the solar radiation transmission through cladding materials covered with condensation on their inner surface a new experimental set-up was constructed. Transmittance experiments were carried out on vertical glass plates and polyethylene films covered with condensation without and with runoff for several incidence angles in the horizontal plane using perpendicularly polarized radiation. It was observed that condensation on a glass plate slightly decreased the solar radiation transmittance when compared with the dry state. The reduction in transmittance increased from 0.8% at normal incidence to 8.5% at an incidence angle of 60°. Results for polyethylene pointed out that condensation affected the solar radiation transmission and so the available solar energy in the greenhouse much more than in a glasshouse. At normal incidence, a transmittance reduction of 20.8% with respect to the dry state was obtained. For higher incidence angles, the transmittance reduction decreased gradually to 7.2% at an incidence angle of 60°. For both glass and polyethylene, it was observed that the start of runoff gave rise to a transmittance increase of up to 2% when compared with the phase of condensation without runoff.     

An analysis of solar gain through externally shaded window of buildings

The development of computer software for analyzing the solar gain through windows of buildings is presented. The program which is capable of stating the hourly values of solar altitude angles, azimuth angles and extra-terrestrial intensity is written in the BASIC Language. The main feature of the program is that it can be used to determine the hourly values of normal solar intensity and solar energy incident on windows treated with reveals, over-hangs and side-fins. Application of the software in analyzing the solar gain through windows in some experiments yield results which are as consistent as those done manually. The experiments show that in every case, reveals have the effect of reducing the incident solar intensities, and hence incident solar energy on windows. Further analysis shows that over-hangs are much more effective in shading than vertical side-fins.     

独立风光互补供电系统能量配比性能分析

对全年不同方位角和倾角的太阳能辐射量进行数值模拟,得知方位角南偏西30°倾角35°的倾斜面接收的太阳能辐射量最大。对光伏组件和风力发电机的功率输出影响因素进行了仿真,利用仿真结果计算全年的风光出力,由计算最佳倾斜面的太阳能辐射量和当地实际气象参数数据对风光互补匹配特性进行统计分析,得知风能与太阳能最佳配比为1:0.85,为以后风光互补供电系统的设计提供参考依据。     

建筑窗体玻璃节能研究

本文对建筑中的外门窗在太阳辐射热的传递与利用,对几种玻璃光在不同波段情况有效光的传递等方面作了分析研究,得出了不同的太阳高度角下、建筑不同朝向的窗户应选用的建筑门窗玻璃。并特别指出Low-E玻璃对建筑节能有着突出的优势。