Alcalde-Morales Sergio, Valenzuela Loreto, Serrano-Aguilera J J
CIEMAT - Plataforma Solar de Almería, Crta. Senes, km. 4.5, 04200, Tabernas (Almería), Spain.
Universidad de Málaga, Escuela de Ingenierías Industriales, Campus de Teatinos, s/n, 29071, Málaga, Spain.
Heliyon. 2023 Jul 27;9(8):e18692. doi: 10.1016/j.heliyon.2023.e18692. eCollection 2023 Aug.
This paper presents a thermal study of a cavity receiver designed for a Fresnel-type linear solar collector (LFC). The study utilizes a two-dimensional computational fluid dynamics (CFD) model implemented in ANSYS Fluent. The thermal behavior of air inside the cavity for a Fresnel collector is extensively examined. The receiver consists of a trapezoidal cavity with a set of six parallel absorber tubes, through which a thermal fluid circulates. The cavity has aluminum reflectors on the inner walls and glass window closing the aperture facing the primary reflectors of the solar collector. The two-dimensional numerical model represents a cross-section of the receiver, and aims to provide numerical results that allow to provide algebraic correlations for predicting heat losses in the receiver from the wall temperature of each of the six individual absorber tubes that compose it. The developed model is transient, utilizing the k-ε turbulent model. In addition, the study is completed with an analysis of the behavior of the air surrounding and inside the cavity, to evaluate its thermal performance. For this purpose, the velocity and temperature contours obtained with the two-dimensional model are discussed. Correlations are obtained to know the heat flux between the tubes and the heat loss through the window for any combination of temperatures for each pair of tubes, which has not been yet studied in the literature. The study reveals that radiative losses contribute to 81% of the total heat losses, with the outer tubes temperature being the main responsible for these losses. Furthermore, a dimensionless analysis examines the relationship between the Nusselt and Rayleigh numbers in comparison to reference problems based on canonical geometries dominated by buoyancy-driven flows. The performance is found to be similar to that of a downward hot flat plate.
本文介绍了一种为菲涅耳型线性太阳能集热器（LFC）设计的腔式接收器的热研究。该研究利用了在ANSYS Fluent中实现的二维计算流体动力学（CFD）模型。对菲涅耳集热器腔内空气的热行为进行了广泛研究。该接收器由一个梯形腔和一组六根平行的吸收管组成，热流体在这些吸收管中循环。腔内的内壁有铝反射器，窗口由玻璃封闭，该窗口面向太阳能集热器的主反射器。二维数值模型代表了接收器的一个横截面，旨在提供数值结果，以便为预测由构成接收器的六根独立吸收管中每根的壁温所导致的接收器热损失提供代数关联式。所开发的模型是瞬态的，采用k-ε湍流模型。此外，该研究还通过对腔周围和腔内空气行为的分析来完成，以评估其热性能。为此，讨论了二维模型获得的速度和温度等值线。得到了关联式，以了解每对管子在任意温度组合下管间的热通量以及通过窗口的热损失，这在文献中尚未有研究。研究表明，辐射损失占总热损失的81%，外管温度是这些损失的主要原因。此外，无量纲分析研究了与基于浮力驱动流主导的标准几何形状的参考问题相比，努塞尔数和瑞利数之间的关系。发现其性能与向下的热平板相似。
