双面受热太阳能平板接收器热性能模拟研究

为提高太阳能光热转换效率,建立同轴非完整型平移抛物面聚光系统。分析双面受热平板接收器的能量传递及转换过程,采用热阻网络图的分析方法建立平板接收器的理论计算模型。利用MATLAB 7.0软件编制程序实现了平板接收器的热性能计算。在结构参数、环境参数和进口参数确定的情况下,当吸热板导热系数、厚度和吸热板表面发射率变化时,分析温度、能量及热性能的变化趋势。研究表明：导热系数和吸热板厚度达到一定数值,继续增加对于提高接收器的热性能基本没有太大意义;吸热板表面发射率对热性能影响显著,采用发射率为0.1的选择性涂层可实现能量最大转化;环境温度在0～30 ℃变化时,双面受热比单面受热的热效率提高了8.18%～37.01%。     

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。     

采用真空柱状接收器的碟式集热器光热特性研究

提出利用柱状真空管作为碟式太阳能聚光系统的接收器,强化碟式抛物面太阳能聚光器的接收效率、降低系统对跟踪精度的要求,进而降低整个系统的工程造价,实现系统低成本运行。对系统结构进行光学和传热性能分析,给出几何聚光比随接收器几何参数的变化规律。结果表明,接收器在跟踪误差为0.5°时,几何聚光比仍可达到理想情况时的80%。结合传热学计算和Tracepro光学仿真,得到接收器热损失系数随接收表面温度,以及局部能量聚光随跟踪误差的变化规律,为此类碟式太阳能聚光集热器的优化设计提供依据。     

旋转抛物面误差对聚光性能的影响

采用蒙特卡洛法,建立了太阳光分布、抛物面误差及反射的概率模型,跟踪光线行程,研究了误差对抛物面焦平面上聚光性能影响.研究表明,误差会显著改变焦平面上的聚光比分布和大小,影响旋转抛物面的聚光性能.总体而言,随着最大误差角度增大,旋转抛物面的最大聚光比和总聚光比减小,热点和最远进光的r/R增大.只是在最大误差较小的范围内,最大聚光比基本相等,热点的r/R则会小于理想旋转抛物面.因此,为了对接收器进行合理的设计和性能预测,需要认真分析旋转抛物面误差对聚光性能的影响,并尽可能提高抛物面的制作精度.     

非对称槽式抛物面聚光器的仿真与性能研究

基于光学成像原理,设计了一种由两个不同抛物面组合而成的、适于在太阳能中低温集热领域应用的新型非对称槽式抛物面聚光器。文章介绍了该聚光器的工作原理,并在计算机上三维建模,利用光学分析软件计算了其中所安装的圆管型接收器和平板型接收器的光学效率,分析了接收器上的光线接收率随入射偏角的变化趋势。研究结果表明,新型非对称槽式抛物面聚光器在入射偏角为6°时,圆管型接收器表面的光线接收率达到71%;在最大尺寸条件下,圆管型接收器的接收效果优于平板型接收器;实际测试所得的装置聚光热效率为34%。     

空间薄膜抛物面聚光系统辐射能流密度的研究

结合薄膜聚光器的光学特性,同时考虑空间太阳形状模型、薄膜表面反射误差的概率模型,采用蒙特卡罗光线追迹法计算空间薄膜抛物面聚光系统接收面上辐射能流密度,分析薄膜聚光器的表面反射误差、焦径比、接收器的遮挡作用和接收器的位置对系统接收面上辐射能流密度分布的影响,为空间薄膜聚光系统的参数设计和性能分析提供参考。     

抛物面槽式太阳能SolTrace 模拟与实验分析

结合抛物面槽式聚光器的光学特性,应用Sol Tarce光学仿真模拟软件,采用蒙特卡洛射线追踪法对设计搭建的呈东西轴布置的抛物面槽式聚光集热实验系统,建立光学系统模型并进行Sol Tarce模拟分析,获得抛物面槽式吸热管在当天不同时刻下及不同太阳直射辐照度下的有效辐射能通量和抛物面槽式吸热管壁面的能流密度分布,并将模拟得到的结果与实测实验数据进行对比分析,结果表明:模拟结果与实验数据具有较好的一致性,最小及最大偏差分别为8.1%和16.4%,实验数据可较好地验证Sol Tarce模拟系统的可行性及模拟结果的可信度,抛物面槽式吸热管吸收太阳辐射能受太阳光入射角和太阳辐照度的影响较大。模拟结果能够有效地反映聚光型太阳能热发电系统的光学性能及热性能,为聚光型太阳能热发电系统的设计与优化以及工程应用提供参考依据。     

槽式太阳能集热管热性能评估方法

真空集热管是槽式太阳能聚光集热系统的核心部件之一.集热管工作过程中通过辐射换热、对流换热和热传导的方式将热量传递给环境,这部分传递到环境中的热量称为集热管的热损失.真空集热管的热损失是聚光集热系统热损失或总能量损失的主要组成,在很大程度上决定着聚光集热器的光-热转换效率,因此对集热管热性能的正确评估对聚光集热系统的研究至关重要.本文对槽式太阳能集热管热性能的计算、评估分析方法等进行了分析.     

圆柱型碟式太阳能接收器聚光集热耦合实验研究

太阳能热发电系统中聚光、集热协同进行,聚光太阳能能流极不均匀,对能量转换效果有较大影响。为避免太阳直射辐照度的变化对实验结果的影响,采用碟式聚光器和圆柱型接收器,搭建了两套结构一致的实验系统,同时开展聚光和集热实验,提高了实验数据的准确度。接收器采光口能流分布是聚光和集热效率研究的基础,利用水冷式能流密度传感器,在接收器集热实验时同步测量了接收器采光口能流密度分布,通过面积剖分,得到接收器入射能流。开展集热实验,分析了太阳能直射辐照度和工质流量变化对系统集热效率的影响。研究结果表明:随直射辐照度增加,系统入射功率、输出功率和接收器采光口截获功率不断增加,但上升趋势逐渐变缓;聚光器聚光效率、接收器热效率、系统总热效率均呈下降趋势,且斜率逐渐变缓;随着传热工质流量增加,接收器腔内壁面温度下降且温度场梯度变小,减少了接收器热损失,系统输出功率不断加大,总热效率不断提高。     

聚光太阳能热发电中吸热器吸收涂层的选择

对各类聚光比的聚光太阳能热发电中的吸热器吸收涂层进行了研究,同时对耐高温太阳吸收涂层进行了高温热处理和辐射性能测试.研究表明,菲涅耳线式和抛物面槽式聚光吸热器由于聚光比较小,吸热体表面温度较低,主要采用选择性涂层以提高吸热表面温度和吸热效率;而塔式和抛物面碟式聚光吸热器由于聚光比大,吸热体表面温度较高,高温时的吸收涂层在红外波段的吸收率下降,因此主要采用高吸收率的耐高温涂料为太阳吸收涂层.     

Experimental study of a refrigerant charged solar collector

The performance of a heat-pipe solar collector was investigated experimentally using refrigerants R11 as the working fluid. The unit is fabricated locally and its performance is evaluated under Beirut Solar conditions. The heat transfer from the heat pipes to the hot-water storage tank took place through a circular end condenser section of the heat-pipe integrated within the collector frame. Tests of single heat pipes showed that the thermal performance of the heat pipe were dependent on its tilt angle, condenser section length and configuration, and type of internal wick used. A circular condenser end of the heat-pipe performed better than a straight condenser due to increased surface area for heat transfer. The R11-charged solar collector with integrated condenser for secondary cooling of water had an efficiency in early operation hours that reached values higher than 60% for the forced circulation mode. The instantaneous system efficiencies varied from 60 to 20%, which are in the range of conventional water solar collectors. System response was fast and sensitive to the incident solar radiation. The thermosyphonic mode of the system operation generated build up of stored energy in the condenser, resulting in oscillating-type flow thus reducing system efficiency below values obtained with forced circulation. © 1998 John Wiley & Sons, Ltd.     

Performance analysis of a solar cooker in Turkey

A box‐type solar cooker is designed and its thermal performance is analysed experimentally. The cooker tracks the sun in two axes, altitude and sun azimuth, by hand control for hourly periods. The experimental results show that the tested cooker may be assumed suitable in some cooking processes for specific country conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance investigation of a solar water distiller integrated with a parabolic collector using fuzzy technique

A recent study of the design of solar distillation with solar radiation concentration was carried out by an independent device. Transformer oil was used as a fluid to transfer heat to the distilled basin. The design and operational variables are essential, such as distiller dimensions, concentration ratio, pressure, and temperature. A mathematical model was proposed to simulate the system for 2 July 2018 from 10 am to 4 pm  in the climatic conditions of the city of Kirkuk, Iraq. Fuzzy logic (FL) was used to select the affected parameters: water temperature (T_w), water pressure (P_w), glass temperature (T_g), and vapor pressure (P_g) which have a separated membership function that control the linguistic variables. The results showed that the best performance of the distiller is at T_w = 100°C, P_g = 10 000 Pa, T_g = 20°C, and P_w = 20 000 Pa, and concentration ratio of 30. This study used FL to analyze solar distiller performance and identify optimum temperature, pressure, and concentration ratio on the productivity of solar distiller.     

一种新型太阳能海水淡化系统的实验研究

介绍了一种新型的太阳能海水淡化方法,即结合太阳能空气集热器和太阳能热管、利用空气增湿除湿来实现海水淡化。分别进行了电吹风模拟太阳能空气集热器的蒸发器实验,以及结合3m2太阳能空气集热器和热管集热器的实际装置实验。结果表明,影响蒸发量的主要因素为热空气温度、热空气流量、初始水量、水温、出气孔直径和数量。实验结果表明,装置可获得的最大冷凝量为790g/h,计算出系统的产水率和热力学效率分别为5.59×10-5kg/kJ和12.4%。     

Performance of a bi-layer solar steam generation system working at a high-temperature of top surface

Many efforts have been focused on enhancing the vapor generation in bi-layer solar steam generation systems for obtaining as much pure water as possible. However, the methods to enhance the vapor temperature is seldom studied although the high-temperature vapor has a wide use in medical sterilization and electricity generation. In this work, to probe the high-temperature vapor system, an improved macroscopic heat and mass transfer model was proposed. Then, using the finite element method to solve the model, the influences of some main factors on the evaporation efficiency and vapor temperature were discussed, including effects of the vapor transport conditions and the heat dissipation conditions. The results show that the high-temperature vapor could not be obtained by enhancing the heat-insulating property of the bi-layer systems but by applying the optimal porosity and proper absorbers. This paper is expected to provide some information for designing a bi-layered system to produce high-temperature vapor.     

空气集热器透明蜂窝透过率的二维理论推导

透明蜂窝的太阳透过率是衡量平板式太阳能集热器性能的主要参数.本文考虑入射光线所在平面垂直于集热器表面的情况,从而将光线在蜂窝内部的复杂的传播过程简化为在一个矩形单元内的二维多次反射.根据几何光学原理,推导出蜂窝的有效透过率的计算公式:τe=[(1-Atanθ+N)+(Atanθ-Nρe]τ2ρNe.根据公式,透明蜂窝的有效透过率为入射角θ、材料的透射率τ和反射率ρ、以及蜂窝单元的高宽比A的函数,与蜂窝的具体尺寸无关.该公式提供了计算透明蜂窝透过率的一个简单而有效的方法.     

Experimental comparison of a solar-assisted heat pump vs. a conventional thermosyphon solar system

A solar-assisted heat pump system (SAHPS) for hot-water production has been developed and compared for its experimental performance, under similar ambient conditions with a conventional thermosyphon solar system (CTSS) with a single direct tank. Both systems were monitored from 1993 to 1997 during summer and winter time periods. The performance of CTSS was seriously affected by weather conditions, whereas SAHPS could always operate with no significant variation and with a COP above 3·0. A comparison between the two systems proved the performance of the SAHPS to be better than that of CTSS under all climatic conditions. © 1998 John Wiley & Sons, Ltd.     

“八面玲珑展威风”——介绍一种新的“采用数倍聚光的光伏发电系统”

尽管太阳能是发展潜力最大的可再生能源资源,但由于太阳能光电的成本远远高于风电、生物质发电,使得人们对太阳能的大规模利用还依然是一种奢望。那么,如何使太阳能从“高处不胜寒”的境遇走入寻常百姓家呢?关键在于技术突破!本文介绍的“采用数倍聚光的光伏发电系统”使我们看到了太阳能光电大规模发展的希望。根据陈应天教授的聚光和跟踪理论而开发的这种系统,可以使太阳能光电成本比传统的平板固定式光电技术降低1倍!本文以详实的数据介绍了这项完全自主创新的新技术的特点和经济优势。在我国风电、生物质发电技术落后并受制于国外技术垄断的情形下,这项新技术的示范推广,将是我国在太阳能利用方面的重要突破。     

Mathematical modelling of a thin layer drying of apricots in a solar energized rotary dryer

In this paper we present a mathematical modelling of a thin layer forced solar drying of apricots. An indirect forced convection solar dryer consisting of a solar heater and a rotary column cylindrical drying (RCCD) cabinet was used in the experiments. Air heated by the solar air heater was forced through the apricots by an electrical fan. Moreover, the natural sun drying experiments were conducted for the comparison at the same time. Fourteen different thin layer mathematical drying models were compared according to their coefficients of determination (r,χ², RMSE) to estimate solar drying curves. The effects of the drying air temperature, velocity and the rotation speed of column on the drying model constants and coefficients were predicted by multiple regressions using a linear type model. Copyright © 2004 John Wiley & Sons, Ltd.     

Energy efficiency of a solar drying system

A solar collector, part of a drying system using solar energy as a heat source, was developed and reported previously and used in product-drying applications. In this study, energy efficiency analyses of the drying system in terms of the collector efficiency were investigated. The results obtained show that the present collector used in this solar drying system is an efficient and effective unit for practical drying applications.