Comparison of Heat Transfer in Gravity-Driven Granular Flow near Different Surfaces
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https://doi.org/10.1007/s11630-020-1357-4
Article ID: 1003-2169(2020)00-0000-00
Comparison of Heat Transfer in Gravity-Driven Granular Flow near Different Surfaces GUO Zhigang, TIAN Xing, YANG Jian, SHI Tuo, WANG Qiuwang* MOE Key Laboratory of Thermo-Fluid Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China © Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract: Heat transfer in gravity-driven granular flow has been encountered in many industrial processes, such as waste heat recovery and concentrated solar power. To understand more about Moving Bed Heat Exchanger (MBHE) applied in this field, numerical simulation was carried out for the characteristics of granular flow near different surfaces through discrete element method (DEM). In this paper, both the performances of particles motion and heat transfer were investigated. It’s found that, even though the macroscopic granular flow is similar to fluid, there is still obvious discrete nature partly. The fluctuations of parameters in granular flow are inevitable which is more obvious in the circular tube cases. A special phenomenon, where competition motion is found, is resulted from discrete nature of particles. In terms of heat transfer, overall heat transfer coefficients for plate are higher than that of tube owing to better contact between particles and wall. However, due to competition motion, particles in high temperature tend to contact the tube, which is beneficial to heat transfer in some local zones. The heat transfer characteristics above will also affect the temperature distribution near the outlet of different geometries.
Keywords: gravity-driven granular flow, discrete element method (DEM), heat transfer, numerical simulation
1. Introduction Nowadays, heat recovery from dense gravity-driven granular flow has been more concentrated on. It makes a vital contribution to waste heat recovery in industrial process [1, 2] and to the system of Concentrated Solar Power [3‒5], which is critical to sustainable development of human society. Especially, solid powder produced in industrial process contains huge high-temperature waste heat [1]. In the past, fluidized bed was commonly known in the occasion. Nowadays, moving bed heat exchanger (MBHE) is gradually implemented due to lower cost [6, 7], which could also provide a potential alternative with lower heat loss [8]. Thanks to their meaningful
Received: Sep 28, 2019
applications, the interest in gravity-driven granular flow with heat transfer has increased recently. The granular flow is sensitive to geometry factors, particles parameters and loading conditions. There have been different types of heat exchange surface researched and adopted before. Patton et al. [9] presented the heat transfer correlation about granular flow around the incline plate through their experiment. Natarajan and Hunt [10] studied the correlation between flow rate and heat transfer coefficients experimentally, where heat transfer would b
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