Numerical analysis of thermal energy charging performance of spherical Cu@Cr@Ni phase-change capsules for recovering hig
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Zhijian Penga) School of Engineering and Technology, China University of Geosciences, Beijing 100083, China
Bingqian Ma National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Peilun Wang School of Engineering and Technology, China University of Geosciences, Beijing 100083, China; and State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Jianqiang Lib) National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China (Received 29 October 2016; accepted 30 November 2016)
Metallic phase-change materials (PCMs) attract much attention due to their high thermal conductivity in thermal energy storage. Our previous work reported a kind of Cu@Cr@Ni bilayer capsules, which could endure at least 1000 thermal cycles between 1323 and 1423 K without leakage, and might be a potential high-temperature metallic PCM. This study numerically investigates the thermal energy charging performance of Cu@Cr@Ni capsules for recovering high-temperature waste heat at both constant and periodically fluctuant heat transfer fluid temperatures. It was revealed that only a short and slight sloped melting platform existed in the curve of outlet temperature due to the ultrahigh thermal conductivity of copper; with higher inlet velocities, the outlet and mean temperatures of such PCM increased and meanwhile the energy transfer efficiency decreased; the outlet and mean temperatures of the PCM and the liquid fraction in it were rather insensitive to the period of the inlet temperature fluctuation; and the amplitude of inlet temperature fluctuation, 650 K, was sharply reduced to 5 K due to the thermal damping of the PCM.
I. INTRODUCTION
Energy crisis is one of the main barriers constraining the development of human societies. Currently, about 80% of world primary energy consumption comes from fossil fuels, such as coal, oil, and gas, which are finite and generate large amounts of greenhouse gases during use.1,2 To address the energy issues, further increasing the share of energy produced by renewable energy technologies and improving the energy efficiency of fossil fuels are two effective ways. Contributing Editor: Yanchun Zhou Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2016.493
In various industrial processes, there is a considerable amount of waste heat emitted out in the form of high-temperature gases or liquids. For example, the steel-making industry with high energy consumption emits essentially 50% of input energy in the form of high-temperature waste gas.3 And the temperature of the waste heat varies from low grade (e.g., 308–313 K in power plants) to very high one (e.g., 1
