Models of transient heat transfer for central tower receivers: A review

• Main Authors: Marti, Juliette, Antón, Javier Muñoz, Servert, Jorge
• Format: Conference Proceeding
• Language: English
• Subjects: Aerodynamics; Ambient temperature; Computational efficiency; Computational fluid dynamics; Computing costs; Critical components; Differential equations; Empirical equations; Finite element method; Flow velocity; Fluid flow; Free convection; Heat transfer; Mathematical models; Receivers; Semiempirical equations; Simulation; Solar collectors; Steady state; Temperature; Temperature distribution; Thermal analysis; Thermal radiation; Three dimensional models; Transfer functions; Turbulent flow; Two dimensional models
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0034529

Solar Power Tower (SPT) receivers are the most critical component of a SPT power plant, as they receive high incident solar flux on their external face while having a corrosive environment on their internal side. Due to the transient nature of solar energy, a steady-state analysis does not accurately reflect the stresses on the receiver. Current CFD models of the receivers do not simulate the whole receiver, because doing so requires solving models of high computational cost, with meshes of around 8x108 elements. The computational cost of a CFD simulation is directly proportional to the number of elements of the mesh, especially for transient simulations; that is why simplified, but mostly accurate models, are being designed, at least for the initial steps of the receiver design. Some analytical models for external, cavity, and volumetric type receivers subject to transient heat flux have been proposed,. Some authors have used as reference the steady-state external receiver model created by Sánchez-González et al. Xu et al. proposed a 3-D model to simulate the dynamic thermal performance of an external molten salt solar receiver, that could show the temperature distribution evolution after the receiver's exposition to a varying solar flux, the HTF (Heat Transfer Fluid) flow rate, the wind speed and the ambient temperature. Too et al. used an optical-thermal model to investigate transient behavior due to short-time DNI fluctuations. Fritsch et al. compared a simple FEM model to a more complex CFD one. Cagnoli et al. implemented a time-dependent, quasi-1-D system-level model. Samanes and Garcia-Barberena elaborated a model with Modelica, with a 1-D fluid flow configuration through the panels. Zhang et al. used dynamic method called Transfer Function Method (TFM), a second- order differential equation that does not require intermediate temperatures values to predict the outlet temperature of the HTF. Yu et al. proposed a model for a cavity receiver designed for direct stream generation. Zhang et al. divided their model of cavity receiver in four sub-models: thermal conduction in the tube; thermal convection from the outer tube surfaces to the air inside the cavity; thermal radiation heat transfer inside the cavity; thermal convection from the inner surface of the tube to the fluid inside the tube. Wu and Wang studied a volumetric solar air receiver where the volumetric element was a ceramic foam, using semi-empirical equations that describe the behavior of a