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 IkegamiTitle：Measurement of void fraction of ammonia boiling flow in plate evaporatorAnnouncement information:Proceedings of the 3rd International Forum on Heat Transfer
November 13-15, 2012, Nagasaki, JapanKeyword：Visualization, Ammonia, Boiling heat transfer, Plate evaporatorAn 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%.