共查询到19条相似文献,搜索用时 281 毫秒
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本文通过对平板型太阳能空气集热器的理论分析,介绍不同的空气流道厚度、空气流速对空气集热器的散热损失及瞬时效率的影响,为优化设计太阳能空气集热器提供一定的设计依据。 相似文献
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为了提升太阳能在建筑能源供给体系中的比重,形式多样的太阳能集热设备及其系统在建筑领域得到了广泛应用。基于机理分析法,建立了具有单层玻璃盖板的管板式太阳能平板集热器的稳态传热模型。并且针对集热管间距、集热管内径、工质入口温度和工质质量流量等关键参数对集热器集热效率的影响特性进行了数值模拟与分析。结果表明,建立的该稳态传热模型是可行的;此外,在其余参数值保持不变的情况下,减小集热管间距或增加集热管内径均可使集热器瞬时效率增大;增大工质入口温度会导致集热器瞬时效率下降;而增大工质质量流量会提升集热器瞬时效率。这些结论对于太阳能平板集热器在太阳能建筑一体化的实际应用中,具有一定的参考作用。 相似文献
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建立多孔盖板型太阳能平板空气集热器的数值计算模型,利用已有实验数据验证模型的准确性。基于该数值模型研究单位面积系统风量、太阳辐射照度和集热层吸收率对集热器热性能的影响。结果表明,多孔盖板型太阳能平板空气集热器的热性能较普通平板集热器有明显改善。系统风量增大,集热效率相应地增大,而空气通过集热器的压力降也会迅速增大,从而造成系统风机耗电量增加,所以应综合考虑系统的热性能和风机耗电量,合理选择系统风量。空气温升随太阳辐射照度增大而升高,并且接近线性增长,集热效率随着辐射照度增大呈缓慢下降趋势。集热效率随着集热层吸收率增大而显著增大,且接近线性增长。 相似文献
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为提高太阳能双效集热器的集热效率,本文对传统平板式太阳能双效集热器和L型翅片式集热器进行数值模拟,对比分析空气集热模式和空气-水复合集热模式的传热特性,并研究空气和水的流量以及翅片高度对L型翅片式双效集热器瞬时集热效率的影响。结果表明:当空气质量流量为0. 016kg/s,水质量流量为0. 018 kg/s时,L型翅片式双效集热器集热效率比传统平板式集热效率提高了9%;集热器中水瞬时集热效率和空气的瞬时集热效率存在相互制约的关系,但随着空气质量流量或者水质量流量的增加,集热器瞬时效率均有所提高;增加翅片高度可以有效的提高集热器的集热效率。 相似文献
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本文提出了一种正弦型肋片太阳能空气集热器,采用三因素三水平的正交试验法,对不同肋片参数的模型进行数值模拟,得出最优肋片参数组合为:波纹幅值15mm,波纹周期100 mm和肋片高度45 mm.研究表明:在10时至15时的典型工况下,太阳辐射照度变化集热效率的影响较小.空气流量在0.03~O.08kg/s范围内,相较平板型肋片太阳能空气集热器,正弦型肋片太阳能空气集热器的平均集热效率高约4.9%、热迁移因子高约0.045,其热损系数则降低0.112 W/(m2·K),表明优化后太阳能空气集热器具有较高的集热性能和较低的热损失. 相似文献
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介绍了带遮阳百叶的热通道玻璃幕墙的简单数学模型。该幕墙由外侧单层玻璃幕墙和内侧中空玻璃幕墙组成热通道,通道中内置遮阳百叶以减少太阳能透射得热。在夏热地区,空气在通道中被太阳辐射加热,处于自然通风状态之下。列出了稳态条件下系统的热平衡方程,通过线性矩阵求解了太阳辐射和外界环境温度分别改变时,两个玻璃和通道内两个空气层及百叶的平均温度。计算模拟表明,内置遮阳百叶的热通道幕墙的内层中空玻璃的外表面温度较传统单层幕墙的表面温度有明显降低;与无遮阳百叶的热通道幕墙相比,室内透射得热量有很大减少,传热系数也比中空玻璃和无遮阳百叶的热通道幕墙有显著降低。 相似文献
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This paper presents an experimental energy and exergy analysis for a novel flat plate solar air heater (SAH) with several obstacles and without obstacles. For increasing the available heat-transfer area may be achieved if air is flowing simultaneously and separately over and under the different obstacle absorbing plates, instead of only flowing either over or under the different obstacle absorbing plates, leading to improved collector efficiency. The measured parameters were the inlet and outlet temperatures, the absorbing plate temperatures, the ambient temperature, and the solar radiation. Further, the measurements were performed at different values of mass flow rate of air and different levels of absorbing plates in flow channel duct. After the analysis of the results, the optimal value of efficiency is middle level of absorbing plate in flow channel duct for all operating conditions and the double-flow collector supplied with obstacles appears significantly better than that without obstacles. At the end of this study, the exergy relations are delivered for different SAHs. The results show that the largest irreversibility is occurring at the flat plate (without obstacles) collector in which collector efficiency is smallest. 相似文献
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为了有效提高太阳能的热利用率,本文运用对流换热场协同理论对太阳集热墙通道中的气流速度场和温度场进行了研究,探讨了通道内温度梯度的方向和气流速度比(u/v)对场协同角及对流换热贡献率的影响规律。研究得出:太阳集热墙通道中的场协同性主要取决于集热墙板的形状和通道中气流的输运工况,改善集热墙板的形状可形成有益于对流换热的温度梯度方向角(θ);当θ一定时(θ≠0°),随着气流速度比的增加,对换热的贡献亦增加,且θ越大,效果越明显。由此提出了优化太阳集热墙集热板的思路,设计了一种带孔折型集热板的太阳墙系统并进行了实验验证。 相似文献
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Thermal performance analysis of the glass evacuated tube solar collector with U-tube 总被引:1,自引:0,他引:1
In this paper, based on the energy balance for the glass evacuated tube solar collector with U-tube, the thermal performance of the individual glass evacuated tube solar collector is investigated by analytical method. The solar collector considered in this study is a two-layered glass evacuated tube, and the absorber film is deposited in the outer surface of the absorber tube. The heat loss coefficient and heat efficiency factor are analyzed using one-dimensional analytical solution. And the influence of air layer between the absorber tube and the copper fin on the heat efficiency is also studied. The results show that the function relation of the heat loss coefficient of the glass evacuated tube solar collector with temperature difference between the absorbing coating surface and the ambient air is nonlinear. In the different ambient temperatures, the heat loss coefficient of the solar collector should be calculated by different expressions. The heat efficiency factor will be subject to influence of air layer between absorber tube and the copper fin. Specially, the influence is remarkable when the heat loss coefficient of the collector is large. When the synthetical conductance amounts to 5 W/m K, the solar collector efficiency decreases 10%, and the outlet fluid temperature decreases 16% compared with the case which the air thermal resistance is neglected. And the surface temperature of the absorbing coating increases 30 °C due to the effect of air thermal resistance. So the surface temperature of the absorbing coating is an important parameter to evaluate the thermal performance of the glass evacuated tube solar collector. 相似文献
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夏热地区热通道玻璃幕墙的热工数学模型 总被引:3,自引:2,他引:1
本文介绍了热通道玻璃幕墙的简单数学模型。模型的物理概念和Trombe墙相似。该幕墙由外侧单层和内层中空玻璃组成热通道。列出稳态状态下热通道的热平衡方程,通过线性矩阵求解了两个玻璃和通道内空气的半均温度,并使用热阻网络表达在太阳辐射条件下,热通道的传热过程。计算机模拟表明,夏热地区热通道幕墙内层中空玻璃的外表面温度较传统幕墙的表面温度有明显降低,由太阳透射引起的房间得热也有较大减少。 相似文献
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Dr F. Haghighat 《国际自然能源杂志》2013,34(3):135-148
The effects of the thermal and hydrodynamics entry length for both laminar and turbulent flow regimes within an air-heating solar collector have been studied using a numerical procedure. Two internal arrangements were considered: (1) air passing on both sides of the absorber (parallel flow), and (2) use of finned and other augmented surfaces. Results of the analysis showed that the temperatures of the cover plates for the parallel flow collector were lower than if the air had passed on only one side of the absorber plate (single flow). Consequently, the heat losses were reduced and the efficiency of the parallel flow collector was increased. Also the pumping power per unit energy gained by the collector for parallel flow mode was less than that for the single flow mode. By using a finned surface, the temperatures of the cover plates were lower than for single and parallel flow and consequently the heat losses were reduced and the efficiency of the finned surface collector was increased. But in this case, the pumping power per unit energy gained by the collector and operating costs also increased. 相似文献
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田琦 《建筑热能通风空调》2007,26(3):51-54,59
在U型管式全玻璃真空管集热器能量平衡分析的基础上,推导了集热器热损系数、效率因子等性能参数计算公式,其理论计算结果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温和环境温度之差是非线性关系,将两者的计算关系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接触热阻后,采用U型管连接方式不会对热水系统集热器效率造成太大影响。 相似文献
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An experimental study of air heating system was carried out using a parabolic trough collector with a U-tube aluminium heat exchanger. An evacuated tube placed at the focal length of the parabolic trough collected the solar radiations reflected from the surface of parabolic trough. The air was used as a working fluid, which was heated by passing it through a U-shaped aluminium heat exchanger placed inside the evacuated tube. It was found that efficiency of the parabolic trough collector depends on the mass flow rate, solar intensity and use of fins. It was observed that by using fins at a high mass flow rate of 4.557?kg/h, the maximum temperature of 126°C was achieved which is 13.27% more than the maximum temperature obtained without fins. Furthermore, for a low-mass-flow rate of 1.69?kg/h, the maximum temperature obtained was 149°C. 相似文献