An analytical study on the thermal characteristics of flat-plate and evacuated solar collectors

In this study, we highlighted differences in the standards used in performance tests of solar collectors. We analyzed testing results for different types of solar collectors to determine the effects of the collector area and mass flow rate, which were not necessarily consistent across all tests. Our analysis showed that the factor,F′ (τα), including collector efficiency factor (F′), could be correlated with the flow rate or area regardless of the collector type. Moreover, the collector loss coefficient (F′U _L ) per flow rate or area for an evacuated collector was less that of a flat-plate collector; this was also correlated with the flow rate or area, regardless of the type of evacuated collector. As a result of this analysis, we propose a modified heat loss coefficient that includes the effects of all parameters that can be considered in a performance test and show that this coefficient could better describe the thermal characteristics of various types of solar collectors.     

太阳能集热单元中央控制软件系统实现

中央控制软件系统实现了大规模太阳能集热单元的数据采集、存储、计算等功能;实现了实时监控现场参数、实时监控不同驱动单元运行状态、实时诊断故障、实时存储数据、实时运算集热效率等功能.软件开发采用C/S架构,Server端软件采用MFC框架,界面采用第三方IOCOMP控件,数据库采用SQL Server2005.经过项目实践证明:采用了上述架构的软件开发周期短、人机界面友好、可实现功能丰富、可扩展性良好、系统运行稳定、应用范围广泛.设计的远程监控模块、远程故障诊断模块、数据存储模块等也可以借鉴到其他需要进行远程监控、故障诊断的行业.     

Theoretical study on performance comparison of various solar collectors using binary nanofluids

Journal of Mechanical Science and Technology - The performances of three types of solar collectors using various nanofluids are theoretically investigated; further, by varying the concentration of...     

Reliability-driven design optimization of si solar module under thermal cycling

Journal of Mechanical Science and Technology - The lifetime of solar modules is not only a reliability measure but also an important factor in increasing the competitiveness of the modules against...     

Experimental study on the characteristics of longitudinal fin air-heating vaporizers in different seasons

Air-heating vaporizers are usually used to regasify LNG at satellite areas because of the small demand for natural gas there. The common type of air heating vaporizer which exists in the market is the longitudinally finned type with 8 fins, 50mm fin length and 2mm fin thickness. To contribute in developing an efficient air-heating vaporizer, experiment on finned type air-heating vaporizer using 8 fins, 50mm fin length with 2mm fin thickness (8fin50le)-which exist in the market-and 4 fins, 75mm fin length with 2mm fin thickness (4fin75le), which is proposed, were conducted. Then, both types of vaporizers are compared. The experiments were conducted in one hour by varying the ambient condition and the length of the vaporizer. The ambient air was controlled so that it has the same condition (same temperature, humidity and air velocity) with air condition in every season available and the length was varied 4000mm, 6000mm and 8000mm for each type of vaporizer. Additional experiment with longer duration, i.e., 4 hours and in a single room condition was conducted to validate the previous result. In this experiment, the main aspects in analyzing the characteristics of the air heating vaporizer are the inlet-outlet enthalpy difference and the outlet temperature of the working fluid. LN₂ is used to substitute LNG for safety reasons. The results show that the characteristics of the finned type 4fin75le vaporizer are comparable to the finned type 8fin50le vaporizer.     

Analysis of EL images on Si solar module under thermal cycling

Journal of Mechanical Science and Technology - Thermal cycling (TC) induces defects in solar modules. The electroluminescence technique has been used to characterize the defects of solar modules,...     

On-line thermal dependence study of the main solar cell electrical photoconversion parameters using low thermal emission lamps

This paper presents a non-conventional methodology and an instrumental system to measure the effect of temperature on the photovoltaic properties of solar cells. The system enables the direct measurement of the evolution of open-circuit voltage and short-circuit current intensity in relation to a continuously decreasing temperature. The system uses a high-intensity white light-emitting diode light source with low emissions of radiation in the infrared region of the electromagnetic spectrum, resulting in a reduced heating of the photovoltaic devices by the irradiation source itself. To check the goodness of the system and the methodology designed, several measurements were performed with monocrystalline silicon solar cells, dye-sensitized solar cells, and thin-film amorphous silicon solar cells, showing similar tendencies to those reported in the literature.     

Analytical design and analysis of mismatched Smith predictor

In this paper, an analytical design method is developed for the mismatched Smith predictor on the basis of the internal model control (IMC) method. Design formulas are given and design procedure is significantly simplified. One important merit of the proposed method is that the response of the closed loop system can be easily adjusted. The relation between the controller parameter and the system response is monotonous. In addition, necessary and sufficient condition for the robust stability of mismatched Smith predictor is also given. It is shown that the proposed method can provide good performance for perfectly matched system and a better response for mismatched system. Several numerical examples are given to illustrate the proposed method.     

VSAP软件在碟式太阳能热发电系统设计中的应用

进行碟式太阳能热发电系统结构设计的关键是保证其可靠性和稳定性,为此,本文用VSAP有限元软件完成了系统结构的设计计算与分析,并在此基础上解决了聚光器配重、改善系统稳定性等问题。     

Relation of change in geometrical parameters in the thermal performance of solar chimney

Journal of Mechanical Science and Technology - The article deals with the effects of change in dimensions of solar chimney upon the thermodynamic characteristics of the air flowing inside it. The...     

塔式太阳能热发电站定日镜面形检测专用仪器的研制

对于塔式太阳能热发电系统的定日镜,其反射面法线倾角的精度是影响定日镜工作效率的主要光学因素,因此法线倾角也是面形检测的指标.据此,我们提出用基于激光束偏转法的定日镜单元面形检测方法和定日镜主镜安装误差在线检测的方法,研制了相应的检测设备和软件.检测了位于北京的1MWe太阳能塔式热发电示范电站的由55块1.8182 m2(六边形反射镜)定日镜单元组成的100 m2主镜,检测精度优于0.1 m·rad.     

Analysis of thermal performance and thermal stress using two-dimensional thermoelastic model for a 50 MWe external cylindrical solar receiver

Journal of Mechanical Science and Technology - The thermal stress arisen from highly inhomogeneous solar radiation and temperature distribution during operation is mainly responsible for the...     

船用齿轮箱稳态热分析

研究在良好润滑条件下高速重载船用齿轮箱的稳态热传递过程.应用热网络法建立关键部件的热平衡方程组,建立了传动系统功率损失、热阻及对流换热系数的计算模型.利用MATLAB求解热平衡方程组得各关心节点的温度.     

A thermal elastohydrodynamic analysis of flats

A thermal Reynolds equation is developed for a lubricant with an exponential viscosity—temperature variation and for surface contacts with different temperatures. The equation is used to analyse the formation of a lubricant film on a flat rigid punch approaching an elastic plane. The analyses indicate that thermal effects play an important role in controlling the film thickness in such contacts.     

A three-crucible version of thermal analysis

The operating technique and benefits of three-crucible differential thermal analysis are discussed. Using this method, the temperatures and heat effects of iron phase transitions were determined: 773±3°C (α→β), 923±4°C and 10.2±0.8 J/g (β→γ), 1400±3°C and 17.0±1.0 J/g (γ→δ), and 1539±4°C and 250±20 J/g (°→liquid). The temperature of (α→β) beryllium transition (1274±5°C), its melting point (1292±5°C), and the interval of BCC Be (18±5°C) were also measured. The total heat of both trnasitions is 15.1±0.7 kJ/mol, composed of the heat of the α→β transition (7.5±0.4 kJ/mol) and the heat of melting (7.6±0.4 kJ/mol). *** DIRECT SUPPORT *** A31DG005 00013     

Performance analysis of double-flow double-exposure solar air heater

Journal of Mechanical Science and Technology - This work analytically investigates the thermal and thermohydraulic performances of double-flow double- and single-exposure solar air heaters with...     

太阳能汽车车身外形设计要素分析

太阳能汽车利用太阳能驱动且无有害排放物,被称为"未来汽车"。以太阳能汽车为主题,重点介绍了国内外具有代表性的各种太阳能汽车车身外形,分析了车身外形设计要素,认为降低空气阻力、减小滚动阻力,以及增加太阳能的采集,可以有效减少能耗、提高能效。着重从低风阻、车身轻量化,以及太阳能电池板放置来探讨太阳能汽车车身外形的设计。     

永磁同步电机的热路分析及热阻参数测试

针对永磁同步电机设计、参数优化和热分析等问题,对永磁同步电机的热路法温度计算进行了研究,建立了考虑安装和冷却方式的热路模型,提出了一种热路关键参数的测试方法,测试了机壳与空气间的等效热阻、端盖与空气间的等效热阻、安装板与空气间等效热阻,绕组与定子铁芯之间的等效热传导系数,机壳与定子铁芯之间的等效空气隙厚度、端盖与机壳间的等效空气隙厚度、安装板与端盖之间的等效空气隙厚度等热路参数.同时对热路模型进行了热阻敏感性分析,得到了影响电机温升的主要热路参数.实验结果表明,该热路模型和实验测试数据,可以较准确地计算电机温升,误差在5％以内.该热路模型和实验测试热路参数可为同类型电机的设计以及热分析提供很好的参考.     

基于接触热阻的主轴热特性有限元分析

在考虑了轴承、主轴和箱体接触区域的接触热阻影响的基础上,利用大型有限元分析软件ANSYS对某型号机床的主轴系统进行了温度场建模,并综合分析了整个系统的热态特性.论述了热源和边界条件等因素的计算方法,考虑了以往建模时较少考虑的接触热阻因素,对模型在有、无热阻两种情况下进行了分析、对比.对比结果表明,接触热阻对系统的影响是显著的,对于精密机床的研究,建模时不应忽略这一重要因素.     

油品储运伴热软化水太阳能预热系统应用

为解决原油输送过程中易结蜡,不易流动的问题,利用太阳能代替部分传统能源对工业锅炉24h给热,提供伴热软化水,实现了能源消耗的降低和环境保护。提出了油品储运伴热软化水太阳能预热系统,该系统主要应用于场地受限、高热值、高能耗及高污染工业上,具体表现为将太阳能高效集热装置、储热设备与工业锅炉进行结合改造,为锅炉提供预热软水,并且结合相变储热原理以满足出水温度达到工业要求,保证锅炉太阳能集热器完整、连续地运行。在理论研究的基础上,展开了大量的实验,实验结果验证了该系统的可靠性。研究结果表明,预热系统在日问日照充足时,集热效率高,相变蓄热器具有较好地蓄热和放热效果,放热时间能持续5h-7h以上,满足了原油输送过程对热水的需求。