University of Birmingham The optical efficiency of three different geometries of a small scale cavity receiver for concentrated solar applications
University of Birmingham The optical efficiency of three different geometries of a small scale cavity receiver for concentrated solar applications
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发表时间：
2016
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通讯作者：
Ahmed M. Daabo;S. Mahmoud;R. AL-Dadah
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作者：
Ahmed M. Daabo;S. Mahmoud;R. AL-Dadah
对能源的需求日复一日地持续增长;但与此同时，世界各地对可持续能源的研究也在不断增加。聚光太阳能发电（CSP）可以作为一种高效、低成本的能源转换系统来发电，从而减少对传统化石燃料的持续需求。大多数关于CSP的文献集中在热损失及其与接收器几何形状的关系上;其中这些接收器根据其热效率进行评估。大多数文献往往忽略了通过接收器的几何形状的热增益增强，这有助于增加到工作流体的热传递。本工作集中在光学效率以及热通量分布的三种不同的几何形状。圆柱形，圆锥形和球形的几何形状的腔接收器被认为是与光学和热分析其光学和热行为的目的，使用射线跟踪方法和计算流体动力学（CFD）模型。结果表明，圆锥形的接收器收集，以及吸收，比其他形状，约91%和82%的反射通量能量分别为75%和85%的吸收率较高的量。腔体接收器形状及其吸收比是影响焦点位置的关键参数;因此，取决于这两个参数，每种设计都有最佳距离。使用文献中发现的实验工作的模拟工作的结果进行验证。总之，为了评估热平衡，使用Fluent 15进行了3-D热分析，并确定了三种形状的热损失量。观察到圆锥形接收器经历较低的热损失。为了确保结果更可信，热结果与文献中的实验工作进行了验证，结果显示出良好的一致性。
The demand for energy is continually increasing day after day; but at the same time, investigations around the world into sustainable sources of power are growing in number. Concentrated Solar Power (CSP) can act as an efficient low cost energy conversion system to produce electricity which could lead to reducing the continuous demand on conventional fossil fuels. Most of the literature concerning CSP concentrates on the heat losses and their relationship to the receivers’ geometries; where these receivers are evaluated according to their thermal efficiency. The majority of the literature has often neglected heat gain enhancement by the receivers’ geometries, which helps to increase the heat transfer to the working fluid. This work concentrates on the optical efficiency as well as the heat flux distribution of three different geometries. The cylindrical, conical and spherical geometries of a cavity receiver are considered with the objective of analysing their optical and thermal behaviour optically and thermally, using the ray tracing method and a Computational Fluid Dynamic (CFD) model. The results showed that the conical shape of the receiver gathered, as well as absorbed, a higher amount of reflected flux energy than the other shapes, with about 91% and 82% for 75% and 85% absorption ratios respectively. The cavity receiver shapes and their absorption ratio are key parameters which affect the focal point location; thereby there is an optimum distance for each design depending on these two parameters. The results of the simulated work are validated using the experimental work found in the literature. Overall, in order to evaluate the heat balance, 3-D thermal analysis was employed using Fluent 15 and the amount of heat losses for the three shapes was determined. It was observed that the conical shape receiver experienced a lower heat loss. To ensure more confidence in the results, the thermal outcomes were validated against experimental works in the literature and they demonstrated good agreement.