Validation Methods for Oscillating Motion in Large-Scale Oscillating Heat Pipes for Solar Water Heaters
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초록
Solar thermal energy is particularly advantageous for heating purposes because of its higher efficiency compared with photovoltaic energy. Oscillating heat pipes (OHPs) can further enhance the efficiency of solar thermal systems. The effectiveness of OHPs depends on the oscillating motion of the working fluid inside the tubes. While validating the oscillating motion is important, its direct visual validation is challenging owing to the large scale of the system. Therefore, developing indirect methods to confirm the presence of oscillating motion in large-scale OHPs is essential. In this study, a solar water heater utilizing three sets of large-scale OHPs was fabricated and tested. The temperature and efficiency data were compared with previously validated data from a small-scale reference OHP that exhibited temperature changes synchronized with the oscillatory motion. The analysis was focused on general trends, such as temperature fluctuation patterns and efficiency changes, rather than on direct numerical equivalence. The results suggest that a sudden temperature drop or cessation of the temperature rise indicates the onset and continuation of the oscillating motion. Additionally, a sudden increase in efficiency serves as another indicator. Lastly, a periodic temperature fluctuation suggests continuation of the oscillating motion after its initiation.
Abstract
Solar thermal energy is particularly advantageous for heating purposes because of its higher efficiency compared with photovoltaic energy. Oscillating heat pipes (OHPs) can further enhance the efficiency of solar thermal systems. The effectiveness of OHPs depends on the oscillating motion of the working fluid inside the tubes. While validating the oscillating motion is important, its direct visual validation is challenging owing to the large scale of the system. Therefore, developing indirect methods to confirm the presence of oscillating motion in large-scale OHPs is essential. In this study, a solar water heater utilizing three sets of large-scale OHPs was fabricated and tested. The temperature and efficiency data were compared with previously validated data from a small-scale reference OHP that exhibited temperature changes synchronized with the oscillatory motion. The analysis was focused on general trends, such as temperature fluctuation patterns and efficiency changes, rather than on direct numerical equivalence. The results suggest that a sudden temperature drop or cessation of the temperature rise indicates the onset and continuation of the oscillating motion. Additionally, a sudden increase in efficiency serves as another indicator. Lastly, a periodic temperature fluctuation suggests continuation of the oscillating motion after its initiation.