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Yamaji, Tatsuya*; Koizumi, Yasuo; Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Onuki, Akira*; Kanamori, Daisuke*
Konsoryu Shimpojiumu 2015 Koen Rombunshu (USB Flash Drive), 2 Pages, 2015/08
Experiments of condensing counter-current two-phase flow in a vertical pipe were performed. This study was intended to examine water accumulation in the up-flow side of steam generator U-tubes of a PWR during the reflux cooling stage of a small break LOCA. It has been apprehended that the water accumulation may result in temporary core liquid level depression. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. The experiments were performed by using steam and water at 0.1 MPa. Two kinds of experiments were conducted; visualization experiments by using a transparent test section and quantitative water accumulation evaluation experiments by using a brass test section. Even if water on the inner surface of the test pipe could not flow downward at the lower portion of the test pipe, a part of water became to flow downward at the upper portion of the test pipe since steam velocity decreased because of condensation. Thus, two-phase mixture level was formed in the upper portion of the test pipe, which resulted in the water accumulation in the pipe. The model to predict the water accumulation was proposed. It predicted the water accumulation reasonably well.
Koizumi, Yasuo*; Ito, Kei; Ohshima, Hiroyuki; Otake, Hiroyasu*
Proceedings of 2010 ASME International Mechanical Engineering Congress & Exposition (IMECE 2010) (DVD-ROM), 6 Pages, 2010/11
The gas entrainment rate into liquid by the vortex formed on the free surface was examined experimentally. The flow state of the entrainment was visually observed by using a high speed video camera. The gas entrainment rate into water was measured. A stable vortex was formed in the test vessel. Whether the bottom of the vortex reached the bottom outlet of the vessel was dependent on the velocity at the bottom outlet. Before the vortex tip reached the bottom of the vessel, bubbles were periodically torn off from the bottom tip of the vortex and the bubble-type gas entrainment was observed. After the bottom of the vortex reached the bottom of the vessel, the gas entrainment turned to the vortex-type gas entrainment. When the gas entrainment turned to the vortex-type gas entrainment, the flow state in the outlet pipe changed from the bubbly flow to the churn flow. After the gas entrainment varied from the bubble-type to the vortex-type, the gas entrainment rate increased drastically.
Koizumi, Yasuo*; Ito, Kei; Ohshima, Hiroyuki; Otake, Hiroyasu*
no journal, ,
Gas entrainment from the bottom of a container was examined in the case that there was a free surface with swirl flow and liquid flew out from an outlet at the bottom. Before the bottom of the vortex reached the bottom of the container, bubble-state gas entrainment from the tip of the vortex occurred and the bubbles flew out from the bottom outlet of the container. As the liquid velocity was increased, the bottom of the vortex invaded into the outlet piping and eventually air and liquid phase separation occurred in the piping. The flow state changed to a churn flow, and then to an annular flow and the entrained air flow rate increased considerably as the liquid flow rate was increased.
Yamaji, Tatsuya*; Koizumi, Yasuo; Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Hasebe, Yoshiaki*; Onuki, Akira*; Nishi, Hiroaki*
no journal, ,
Experiments of counter-current two-phase flow of upward steam flow and condensing downward film flow in a pipe were performed. The experiments were intended to examine water accumulation in steam generator U-tubes during intermediate and small break loss-of-coolant accidents of a pressurized water reactor. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. A transparent polycarbonate tube was used as the test tube since flow observation was mainly intended. When the vapor velocity was low, condensate flowed down on the inner wall of the test tube and flowed out from the bottom inlet of the test tube. As the vapor velocity was increased, slug flow came out at the intermediate elevation of the test tube and the condensate flowed up and flowed out from the top outlet of the test tube. At the lower elevation, the condensate flowed down and flowed out from the bottom outlet. This state have not been observed in the water-air experiments. The unique state for the water-vapor condensing counter-current two-phase flow was found out.
Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Hasebe, Yoshiaki*; Yamaji, Tatsuya*; Koizumi, Yasuo; Onuki, Akira*; Nishi, Hiroaki*
no journal, ,
Experiments of counter-current two-phase flow of upward steam flow and condensing downward film flow in a pipe were performed. The experiments were intended to examine water accumulation in steam generator U-tubes during intermediate and small break loss-of-coolant accidents of a pressurized water reactor. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. In the present experiments, the test tube was changed from the polycarbonate tube that had large heat transfer resistance to a bras tube that had low heat transfer resistance so as to cover wide range for the condensing film flow rate. Since the vapor velocity was large in present experiments, the condensate film flowed upward and flowed out from the top outlet of the test tube. A flow state in the test tube was upward annular two-phase flow. Pressure drop between the inlet ad the outlet of the test tube was well expressed with the Lockhart-Martinelli correlation for the two-phase flow pressure drop. The experimental results suggested to promise the possibility for data accumulation in the future.
Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Yamaji, Tatsuya*; Koizumi, Yasuo; Onuki, Akira*; Kanamori, Daisuke*
no journal, ,
Experiments of condensing counter-current two-phase flow in a vertical pipe were performed. This study was intended to examine water accumulation in the up-flow side of steam generator U-tubes of a PWR during the reflux cooling stage of a small break LOCA. It has been apprehended that the water accumulation may result in temporary core liquid level depression. Two kind experiments were performed; single channel experiments and parallel four channel experiments. The inner diameter and the length of the test flow channels were 18 mm and 4 m, respectively. The experiments were performed by using steam and water at 0.1 MPa. It was confirmed that even if water on the inner surface of the test pipe could not flow downward at the lower portion of the test pipe, a part of water became to flow downward at the upper portion of the test pipe since steam velocity decreased because of condensation. Thus, two-phase mixture level was formed in the upper portion of the test pipe, which resulted in the water accumulation in the pipe. The water accumulation in the test pipe in the four channel experiments was smaller than in the single channel experiments. In the four channel experiments, the condensing rate of steam decreased as steam flowed upward although the steam condensing rate was uniform along the channel in the single channel experiments. This difference in the experimental condition between the two kind experiments might result in smaller water accumulation in the four channel experiments than in the single channel experiments.
Koizumi, Yasuo; Yamaji, Tatsuya*; Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Onuki, Akira*; Kanamori, Daisuke*
no journal, ,
Experiments of condensing counter-current two-phase flow in a vertical pipe were performed. This study was intended to examine water accumulation in the up-flow side of steam generator U-tubes of a PWR during the reflux cooling stage of a small break LOCA. It has been apprehended that the water accumulation may result in temporary core liquid level depression. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. The experiments were performed by using steam and water at 0.1 MPa. Two kinds of experiments were conducted; visualization experiments by using a transparent test section and quantitative water accumulation evaluation experiments by using a brass test section. Even if water on the inner surface of the test pipe could not flow downward at the lower portion of the test pipe, a part of water became to flow downward at the upper portion of the test pipe since steam velocity decreased because of condensation. Thus, two-phase mixture level was formed in the upper portion of the test pipe, which resulted in the water accumulation in the pipe. The model to predict the water accumulation was proposed. It predicted the water accumulation reasonably well.