Numerical investigation of flow and heat transfer in a volumetric solar receiver

• Published in: Renewable energy Vol. 60; pp. 655 - 661
• Main Authors: Fend, Th, Schwarzbözl, P., Smirnova, O., Schöllgen, D., Jakob, C.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2013; Elsevier
• Subjects: air; Applied sciences; Channels; combs (social insects); Computing time; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat transfer; mass flow; Mathematical models; Natural energy; permeability; power plants; Receivers; silicon; Silicon carbide; solar collectors; Solar energy; solar radiation; Solar thermal conversion; Solar thermal power plants; Solar tower technology; temperature; Temperature distribution; Theoretical studies. Data and constants. Metering; Thermal conductivity; Volumetric heat transfer coefficient; Volumetric solar receiver; Volumetric solar receiver; Volumetric heat transfer coefficient; Solar tower technology; Renewable energy; Heat flow; Solar tower; Heat transfer
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2013.06.001

Volumetric solar receivers are used in solar power plants to convert concentrated solar radiation into high temperature heat to operate a thermal engine. In general, porous high temperature materials are used for this purpose. Since the pore geometry is important for the efficiency performance of the receiver, current R&D activities focus on the optimization of this quantity. In this study, the influence of slight geometry changes of this component on its temperature distribution and efficiency has been investigated with the objective of an overall improvement. A numerical analysis of the mass and heat transfer through the receiver has been performed. The investigated receiver was an extruded honeycomb structure made out of Silicon Carbide. Additionally, experimental tests have been performed. In these tests, selected receiver samples have been exposed to concentrated radiation. From these tests solar-to-thermal efficiency data have been derived, which could be compared with the calculated data. Two numerical models have been developed. One makes use of the real geometry of the channel (single channel model), the other one considers the receiver to be “porous continuum”, which is described by homogenized properties such as permeability and effective heat conductivity. The experimental parameters such as the average solar heat flux and the mass flow were taken into account in the models as boundary conditions. Various quantities such as the average air outlet temperatures, the temperature distributions and the solar-to-thermal efficiency were used for the comparison. The correspondence between the experimental and numerical results of both numerical models confirms the capability of the approaches for further studies. •An improved ceramic air receiver with a new geometry for solar tower technology has been presented.•Two numerical models to predict the permeability, heat transfer and efficiency properties of the air receiver have been developed and validated.•The influence of the new geometry onto the efficiency could be shown theoretically and experimentally.