期刊
RENEWABLE ENERGY
卷 153, 期 -, 页码 155-167出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.renene.2020.02.011
关键词
Solar energy; Vacuum /evacuated tube; Compound parabolic concentrator (CPC); Heat transfer; Efficiency
资金
- National Natural Science Foundation of China [51866005]
- Science and Technology Planning Project of Yunnan [2017FB092]
Effective utilization of solar energy resource enables to improve the thermal performance of solar evacuated tube. In present work, the back side of solar vacuum tube was coupled with mini-compound parabolic concentrator (mini-CPC). The thermal characteristics of the presented mini-CPC solar vacuum tube were analyzed theoretically and experimentally. A mathematical model of heat transfer for the mini-CPC vacuum tube was established according to the energy conservation, and solved by iterative calculation based on home-built C programming language. The obtained numerical solutions fit in well with the experimental results. Furthermore, analysis indicates the vacuum interlayer plays a crucial role in hindering heat transfer. The thermal-convection resistance (R-co-air,R-conv) dominates the heat loss from cover tube to ambient rather than thermal-radiation resistance (R-co-sky,R-rad). The measured final temperature increment of working water for the mini-CPC and ordinary evacuated tube can reach 63.4 K and 49.8 K, respectively. An experimental result also reveals that the thermal efficiency of the mini-CPC vacuum tube is increased by 24.3%-29.2% compared with that of vacuum tube without mini-CPC, considering various weather conditions. Consequently, the designed mini-CPC evacuated tube shows a preferable performance, which may provide a certain reference in technology for engineering applications. (c) 2020 Elsevier Ltd. All rights reserved.
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