Granular Flow and Heat-Transfer Study in a Near-Blackbody Enclosed Particle Receiver
Granular Flow and Heat-Transfer Study in a Near-Blackbody Enclosed Particle Receiver
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DOI：
10.1115/1.4030970
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发表时间：
2015-10-01
影响因子：
2.3
通讯作者：
Ma, Zhiwen
中科院分区：
文献类型：
--
作者：
Martinek, Janna;Ma, Zhiwen
聚光太阳能发电（CSP）是一种将太阳能转化为电能的有效手段，具有连续，可调度，可再生发电的能量存储能力。然而，当前CSP系统的挑战包括高初始资本成本和电价，并且需要提高出口温度以驱动高效动力循环，同时保持传热介质的稳定性和接收器的热性能。基于固体颗粒的CSP系统是一种替代方案，预计与当前基于硝酸盐的熔盐系统相比具有显着的成本和性能优势。NREL正在开发一种设计，使用气/固两相流作为传热流体（HTF），分离的固体颗粒作为存储介质。该系统的一个关键组成部分是一种新型的近黑体（NBB）封闭粒子接收器，它使用一个阵列的吸收管与颗粒状介质向下流动通过管道之间的通道。NBB封闭式颗粒接收器的发展需要详细的研究接收器的尺寸，颗粒流动条件和传热系数。本研究的重点是模拟和分析颗粒流的模式和由此产生的对流和传导传热的颗粒相使用欧拉欧拉双流体建模技术。在颗粒与壁面接触良好的区域，传热系数预计超过1000 W/m（2）K。然而，模拟预测垂直流动通道中的颗粒/壁分离以及由此产生的传热减少。颗粒流可视化实验证实了颗粒/壁分离，但也表现出复杂的周期性行为和流动不稳定性，产生间歇性侧壁接触，并增强传热以上的理论模拟预测。
Concentrating solar power (CSP) is an effective means of converting solar energy into electricity with an energy storage capability for continuous, dispatchable, renewable power generation. However, challenges with current CSP systems include high initial capital cost and electricity price, and advances are needed to increase outlet temperature to drive high-efficiency power cycles while simultaneously maintaining stability of the heat-transfer medium and thermal performance of the receiver. Solid-particle-based CSP systems are one alternative projected to have significant cost and performance advantages over current nitrate-based molten salt systems. NREL is developing a design that uses gas/solid, two-phase flow as the heat-transfer fluid (HTF) and separated solid particles as the storage medium. A critical component in the system is a novel near-blackbody (NBB) enclosed particle receiver that uses an array of absorber tubes with a granular medium flowing downward through channels between tubes. Development of the NBB enclosed particle receiver necessitates detailed investigation of the dimensions of the receiver, particle-flow conditions, and heat-transfer coefficients. This study focuses on simulation and analysis of granular flow patterns and the resulting convective and conductive heat transfer to the particulate phase using Eulerian-Eulerian two-fluid modeling techniques. Heat-transfer coefficients in regions with good particle/wall contact are predicted to exceed 1000 W/m(2) K. However, simulations predict particle/wall separation in vertical flow channels and a resultant reduction in heat transfer. Particle-flow visualization experiments confirm particle/wall separation, but also exhibit complex periodic behavior and flow instability that create intermittent side-wall contact and enhance heat transfer above that predicted by the theoretical simulations.