Library Subscription: Guest
Begell Digital Portal Begell Digital Library eBooks Journals References & Proceedings Research Collections
Journal of Enhanced Heat Transfer
IF: 0.562 5-Year IF: 0.605 SJR: 0.175 SNIP: 0.361 CiteScore™: 0.33

ISSN Print: 1065-5131
ISSN Online: 1026-5511

Journal of Enhanced Heat Transfer

DOI: 10.1615/JEnhHeatTransf.2017015985
pages 175-195

ANALYSIS OF THE IMPACT OF U-SHAPED STRUCTURE FOR HEADS OF LOOP THERMOSYPHON SOLAR WATER HEATER ON THERMAL STORAGE EFFICIENCY

Chien Huang
Engineering & System Science Department, National Tsing-Hua University 101, Sec. 2, Kuang Fu Rd., Hsinchu, Taiwan
Wei-Keng Lin
Department of Engineering and System Science, National Tsing-Hua University, Hsinchu City, Taiwan
Sung-Ren Wang
Engineering & System Science Department, National Tsing-Hua University 101, Sec. 2, Kuang Fu Rd., Hsinchu, Taiwan

ABSTRACT

Loop thermosyphons are high-efficiency two-phase heat transfer devices capable of transporting thermal energy over long distances. In this paper, we present experiment results for three loop thermosyphon designs for use in solar water heaters: non-U-symmetric loop (asymmetric type), top-U-symmetric loop (symmetric vapor heads type), and both-U-symmetric loop (symmetric vapor and liquid heads type). Experiments were conducted to investigate thermal storage efficiency and temperature distribution under various heat loads and fill ratios. Our results demonstrate the importance of fill ratio and shape of the structure on thermal storage efficiency. The highest thermal storage efficiency values obtained in this study were as follows: non-U-symmetric loop (64.7%), top-U-symmetric loop, (79.8%), and both-U-symmetric loop thermosyphon (73.8%). Our simulation of daily operations revealed that a top-U-symmetric loop provides the best overall performance.