Purpose

This paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver.

Design/methodology/approach

The coupled optical-flow-thermal analysis is carried out on the proposed receiver design. Modelling is performed in two and three dimensions for estimating heat loss by natural convection for an upward-facing cavity. Heat loss obtained in two dimensions by solving coupled continuity, momentum and energy equation inside the cavity domain is compared with the loss obtained using an established Nusselt number correlation for realistic receiver performance prediction.

Findings

It is found that radiation emission from a heated cavity wall to the ambient is the dominant mode of heat loss from the receiver. The findings recommend that fluid flow path must be designed adjacent to the surface exposed to irradiation of concentrated flux to limit conduction heat loss.

Research limitations/implications

On-sun experimental tests need to be performed to validate the numerical study.

Practical implications

Numerical analysis of receivers provides guidelines for effective and efficient solar thermal receiver design.

Social implications

Pressurised air receivers designed from this method can be integrated with Brayton cycles using air or supercritical carbon-dioxide to run a turbine generating electricity using a solar heat source.

Originality/value

The present paper proposes a novel method for coupling the flux map from ray-tracing analysis and using it as a heat flux boundary condition for performing coupled flow and heat transfer analysis. This is achieved using affine transformation implemented using extrusion coupling tool from COMSOL Multiphysics software package. Cavity surface natural convection heat transfer coefficient is obtained locally based on the surface temperature distribution.

中文翻译：

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用于太阳能热应用的混合管式和空腔空气接收器的数值分析

目的

本文旨在处理混合管状和腔体太阳能热接收器的热性能表征。

设计/方法/方法

对所提出的接收器设计进行耦合光流热分析。建模是在二维和三个维度上进行的，用于估计向上空腔的自然对流热损失。通过求解腔域内的耦合连续性、动量和能量方程在二维中获得的热损失与使用已建立的 Nusselt 数相关性获得的损失进行比较，以进行实际接收器性能预测。

发现

发现从受热腔壁到环境的辐射发射是接收器热损失的主要模式。研究结果表明，流体流动路径必须设计在暴露于集中通量辐照的表面附近，以限制传导热损失。

研究限制/影响

需要进行太阳实验测试以验证数值研究。

实际影响

接收器的数值分析为有效和高效的太阳能热接收器设计提供了指导。

社会影响

根据这种方法设计的加压空气接收器可以与使用空气或超临界二氧化碳的布雷顿循环集成，以运行使用太阳能热源发电的涡轮机。

原创性/价值

本文提出了一种新方法，用于耦合来自射线追踪分析的通量图，并将其用作热通量边界条件，以进行耦合流动和传热分析。这是通过使用 COMSOL Multiphysics 软件包中的挤压耦合工具实现的仿射变换来实现的。腔体表面自然对流换热系数是根据表面温度分布局部获得的。