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Measurement of void fraction of ammonia boiling flow in plate evaporator

発表形態:
一般講演(学術講演を含む)
主要業績:
主要業績
単著・共著:
共著
発表年月:
2012年11月
DOI:
会議属性:
国際会議(国内開催を含む)
査読:
有り
リンク情報:

日本語フィールド

著者:
Hirofumi Arima, Fumiya Mishima, Kohei Koyama, Toru Fukunami, Yasuyuki Ikegami
題名:
Measurement of void fraction of ammonia boiling flow in plate evaporator
発表情報:
Proceedings of the 3rd International Forum on Heat Transfer November 13-15, 2012, Nagasaki, Japan
キーワード:
Visualization, Ammonia, Boiling heat transfer, Plate evaporator
概要:
抄録:
The ocean thermal energy conversion (OTEC) system has been attracted attention as renewable energy. This system can generate electricity using thermal energy from ocean. OTEC uses plate heat exchanger as evaporator and condenser and ammonia or ammonia/water mixture as a working fluid, because temperature difference between surface and deep seawater is very small. In order to improve the efficiency of OTEC, improvement in performance of plate evaporator is indispensable. Accordingly, in order to clarify the characteristics of ammonia boiling in plate heat exchanger, the analysis by visualization is performed. In present study, a time variant flow patterns of ammonia is observed by high-speed video camera at three sight glasses on a plate evaporator and a void fraction is analyzed by the movie data using developed original digital processing imaging software. The result shows that it is cleared the void fraction has time variation and the relationship between vapor quality and averaged void fraction. In addition, all flow patterns are observed different from general vertical tube in diabatic flow. It is found that the ammonia flow in plate evaporator is able to be predicted by slip flow model instead of homogenous flow model. In this case, the slip ratio is very larger than that of exiting correlations. Consequently, the new correlation for void fraction is developed to use slip ratio. The correlation can predict the experimental data of void fraction within �20%.

英語フィールド

Author:
Hirofumi Arima, Fumiya Mishima, Kohei Koyama, Toru Fukunami, Yasuyuki Ikegami
Title:
Measurement of void fraction of ammonia boiling flow in plate evaporator
Announcement information:
Proceedings of the 3rd International Forum on Heat Transfer November 13-15, 2012, Nagasaki, Japan
Keyword:
Visualization, Ammonia, Boiling heat transfer, Plate evaporator
An abstract:
The ocean thermal energy conversion (OTEC) system has been attracted attention as renewable energy. This system can generate electricity using thermal energy from ocean. OTEC uses plate heat exchanger as evaporator and condenser and ammonia or ammonia/water mixture as a working fluid, because temperature difference between surface and deep seawater is very small. In order to improve the efficiency of OTEC, improvement in performance of plate evaporator is indispensable. Accordingly, in order to clarify the characteristics of ammonia boiling in plate heat exchanger, the analysis by visualization is performed. In present study, a time variant flow patterns of ammonia is observed by high-speed video camera at three sight glasses on a plate evaporator and a void fraction is analyzed by the movie data using developed original digital processing imaging software. The result shows that it is cleared the void fraction has time variation and the relationship between vapor quality and averaged void fraction. In addition, all flow patterns are observed different from general vertical tube in diabatic flow. It is found that the ammonia flow in plate evaporator is able to be predicted by slip flow model instead of homogenous flow model. In this case, the slip ratio is very larger than that of exiting correlations. Consequently, the new correlation for void fraction is developed to use slip ratio. The correlation can predict the experimental data of void fraction within �20%.


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