共查询到17条相似文献,搜索用时 203 毫秒
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U型管式全玻璃真空管集热器热效率及性能研究 总被引:1,自引:0,他引:1
在能量平衡分析的基础上,建立了U型管式全玻璃真空管太阳能集热器热效率方程,推导了集热器热损系数、效率因子等性能参数的计算公式,理论计算热效率与实验数据吻合良好。计算分析表明,真空管热损系数与吸热管和环境温差并非线性关系,将其关联式按环境温度分段整理将使计算结果更接近实际;涂层发射比对集热器的热效率影响较大,降低涂层发射比是提高集热器效率的有效途径;采取适当的措施降低吸热管与肋片间的接触热阻后,采用U型管连接方式不会时热利用系统集热器效率造成太大影响。 相似文献
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内插式太阳能真空管空气集热器性能分析 总被引:3,自引:0,他引:3
建立了内插管式真空管空气集热器管内空气流动与换热的三维瞬态模型,该模型能够反映真空管吸热层表面辐射热流随时间和各微元位置不同而变化的特点。对不同工况下集热器的主要性能参数及内插管与真空管吸热体表面的温度分布进行预测。同时对横双排内插管式真空管空气集热器进行实验研究,理论和实验相结合,分析了不同工况下集热器的集热温度、瞬时集热效率、热损系数等性能参数,该集热器春夏季在30~80℃的集热温度范围内,集热效率在50%~70%之间,热损系数集中在2~6W/(m~2·K)的范围内。 相似文献
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热管式真空管集热器的热性能研究 总被引:34,自引:9,他引:34
在传热分析的基础上,提出了确定热管式真空集热器的总热损系数、效率因子和热转移因子的计算方法,通过实验,还分别测定了单根真空管和真空管集热器的瞬时效率曲线。实验结果与理论计算值符合较好。 相似文献
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金属吸热体真空管集热器的种类、特点及现状何梓年真空管太阳集热器是在平板型太阳集热器基础上发展起来的新型太阳能集热装置。构成这种集热器的核心部件是真空管,它主要由内部的吸热体和外层的玻璃管所组成。吸热体表面通过各种方式沉积有光谱选择性吸收涂层。由于吸热... 相似文献
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通过对直通式太阳能真空管传热模型的分析,在导出单根带翅片与不带翅片的直通式太阳能真空管的总热损失系数、效率因子、热迁移因子和瞬时效率的基础上,建立了直通式太阳能真空管的性能预测模型;针对由多根并联、顺流布置的直通式太阳能真空管组成的平行流集热器,对比计算了带翅片与不带翅片两种真空管及由其组成的集热器的瞬时效率。结果表明,在工质流量,进口温度,环境温度等条件相同的情况下带翅片的直通式太阳能真空管以及由其构成的集热器的瞬时效率分别比不带翅片的太阳能真空管及集热器提高很多;并联直通式太阳能真空管间的流量分配不均匀性致使集热器的整体效率低于单根真空管的瞬时效率。 相似文献
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常见的太阳热水器分两种形式,平板型和全玻璃真空管式。由于平板式太阳热水器热损较大,冬季环境温度低,平板太阳热水器无法使用,所以近几年平板太阳热水器已逐步退出市场;全玻璃真空管式太阳热水器由于采用了真空绝热技术、光谱选择性吸收技术,使得真空管集热器热损低,集热效率高, 相似文献
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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%。 相似文献
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全玻璃真空太阳集热管光—热性能 总被引:10,自引:0,他引:10
从能量平衡议程导出全玻璃真空太阳集热管的3个光-热性能参数,即热损系数UTL、闷晒太阳曝辐量H和空晒性能参数Y与真空热管理的罩管玻璃的太阳透射比τ、选择性吸收表面的太阳吸收比a、发射比ε、和集热管内的气体压强p,太阳辐照度、环境温度和真空太阳集热管的几何尺寸等函数关系。理论计算的真空太阳集热管的3个热性能参数与实验的结果比较一致。上述全玻璃真空太阳集热管的光-热性能参数已经被国家标准《全玻璃真空太阳集热管》(GB/T17049-1997)采用。 相似文献
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R.K. Mazumder N.C. Bhowmik M. Hussain M.S. Huq 《Energy Conversion and Management》1986,26(3-4):313-316
Tubular receivers with an evacuated space between the absorber and concentric glass cover to suppress convection heat loss are employed as absorbers of linear concentrators in the intermediate temperature range. A knowledge of their heat loss factor is important for a study of the thermal performance of such solar concentrating systems. The heat loss factor of a collector can be calculated by solving the governing heat transfer equations or estimated from an empirical equation, if available. The governing equations must be solved simultaneously by iterations, but this is tedious and cumbersome. Although several correlations exist for determining the heat loss factor for flat-plate collectors and non-evacuated tubular absorbers of linear solar collectors, there is no available correlation for predicting the heat loss factor of evacuated receivers.
A correlation to calculate the heat loss factor (UL) of evacuated tubular receivers as a function of variables involved (absorber temperature, emittance, diameter and wind loss coefficient) has been obtained. The correlation developed by a least square regression analysis predicts the heat loss factor to within ±1.5% of the value obtained by exact solution of the simultaneous equations in the following range of variables: wind loss coefficient, 10–60 W/m2°C; emittance, 0.1–0.95; and absorber temperature, 50–200°C. 相似文献
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The filled-type evacuated tube with U-tube, in which the filled layer is used to transfer energy absorbed by the working fluid flowing in the U-tube, is proposed to eliminate the influence of thermal resistance between the absorber tube and the copper fin of the conventional evacuated solar collector. In this paper, the thermal performance of the filled-type evacuated tube with U-tube was researched by means of theoretical analysis and experimental study. The temperature of the working fluid in the flow direction was obtained, and the efficiency of the evacuated tube was also calculated, based on the energy balance equations for the working fluid in the U-tube. The effects of the heat loss coefficient and the thermal conductivity of the filled layer on the thermal performance of the evacuated tube were studied. In addition, the test setup of the thermal performance of the filled-type evacuated tube with U-tube was established. The evacuated tube considered in this study was a two-layered glass evacuated tube, and the absorber film was deposited in the outer surface of the absorber tube. The results show that the filled-type evacuated tube with U-tube has a favourable thermal performance. When the thermal conductivity of the heat transmission component is λc = 100, the efficiency of the filled-type evacuated tube with U-tube is 12% higher than that of the U-tube evacuated tube with a copper fin. The modelling predictions were validated using experimental data which show that there is a good concurrence between the measured and predicted results. 相似文献
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The results of detailed measurements and calculations of the properties of Sydney University/Nitto Kohki evacuated collector tubes have been used to develop a formula for the instantaneous heat extraction efficiency η of a collector panel incorporating the evacuated tubes. The instantaneous efficiency depends on ambient temperature, mean fluid temperature in the collector, solar flux and the design of the manifold used to extract heat from the glass absorber tubes. Manifold design determines the mean temperature difference between absorber tube surface and mean fluid temperature for given operating conditions, and strongly affects the efficiency η of a collector panel. Neither changes in the number of evacuated tubes per unit area of collector, nor variations in solar flux, significantly alter the efficiency decrement Δ η0 associated with a particular manifold design. Calculated efficiencies agree well with experimental results for collector panels incorporating manifolds of various designs. The formula for efficiency η allows detailed analysis of the relative importance of various energy loss mechanisms in a collector. 相似文献
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针对热水作工质时真空集热管内普遍存在的冻结、腐蚀等问题,本文采用空气作工质,推导了空气作工质时真空集热管的集热效率、热损系数和集热管出口温度的方程,分析了影响空气作工质时各项参数对集热器热性能的影响。通过改变集热管进口空气流量来获得尽可能高出口温度的热空气,从而降低热损系数,提高集热效率。此外,由于热空气可以直接送入干燥室干燥物料,不需要二次转换,节能效果好。由理论分析和试验结果可以预见,利用空气作工质的真空传热管具有潜在的应用价值和前景。 相似文献