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Volume 67, Issue 1
Displaying 1-5 of 5 articles from this issue
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Shigemasa HASHIMOTO, Masujiro SHIMIZU, Nobuo MIYAZAKI, Masayoshi NAKAW ...2005 Volume 67 Issue 1 Pages 3-9
Published: January 15, 2005
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSSnow pit observations were carried out at Nagaoka, Niigata Prefecture, on February 22 and 23 in 2001, while the snow layers were at the melting point. We observed water content and took the photographs for grain size analysis at every hour or two hours in daytime.
Water contents in snow layer were preserved about 10%. It was shown that the grain-coarsening rate in 10% water content was about one tenth in 50% water content. The temporal change of isotope content was calculated by use of the model that constructed for wet snow layers in a closed system under the isothermal condition at 0°C, based on the fractionation between snow particles and liquid water, in association with the coarsening of snow particles. The calculation results compared with field observations. It was suggested that the isotope concentration of the pore water which flows downward from the snow surface contributed significantly the isotope change of snow particles greatly.View full abstractDownload PDF (5328K) -
2nd report:Heat exchange characteristics under steady continuous operation and estimation of the required sizeYoshitaka KAWADA, Takero HIROCHI, Shuichi YAMADA, Masataka SHIRAKASHI, ...2005 Volume 67 Issue 1 Pages 11-21
Published: January 15, 2005
Released on J-STAGE: August 07, 2009
JOURNAL FREE ACCESSIn our previous paper, a vertical cylindrical vessel with upward flow was found to be most recommendable as the ice-water direct contact heat exchanger (DCHE) from the viewpoint of practical application. In this work, the heat exchange characteristics of this type DCHEs under steady continuous operation were investigated to clarify the DCHE size required for given running conditions. Chip ice with about 10mm particle size and natural granulated snow were used as test ice particles. The relationship between the ice-particle bed thickness and the ratio of the representative temperature difference at outlet to inlet of the heat exchange section (inlet-outlet temperature difference ratio) collapses on a single curve irrespective of the heat exchange section length, the ice fraction of supplied mixture and the flow velocity in the vessel. The granulated snow was shown to be less suitable than the chip ice since the ice-particle bed was thicker due to the cohesive nature of particles. The heat exchange rate per unit ice-particle bed volume and unit temperature difference was proportional with the flow velocity irrespective of other conditions. Based on the results described above, we presented a procedure to decide the size of DCHE applied to the user-side system combined with a conventional platetype heat exchanger (PHE) . The size of the DCHE was shown to be smaller than the combined PHE by the factor of hundreds. This result shows that the DCHE can be easily applied to the existing chilled water system to enhance its cooling capacity.View full abstractDownload PDF (1085K) -
Kenichiro MATSUKI, Chihiro YAMASHITA, Fumitaka YANAGISAWA, Osamu ABE2005 Volume 67 Issue 1 Pages 23-32
Published: January 15, 2005
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSTo reveal chemical characteristics of rime in 2002/2003, rime samples were collected at 1670m altitude on Mt. Zao, Yamagata Prefecture, Japan, from December 6th 2002 to April 1st 2003. Mt. Zao is suitable for monitoring air pollution because there is no source of exhaust such as volcano or human emission west of Mt. Zao.
The Yellow sand phenomenon occurred frequently in 2000, but not 2002. Concentrations of soluble substances and particulate matter in the rime were measured. Mean pH was 4.2 in 2002/2003. The total acidification component (nssSO42- + NO3-) was always more abundant than the neutralization component (nssCa2+ + NH4+) . Mean concentrations of nssSO42-, NO3- and NH4+ were the same in 2000/2001 and 2002/2003. However, mean concentrations of nssCa2+ and particulate matter in 2002/2003 were almost half those in 2000/2001. The concentration of nssCa2+ was closely related to that of particulate matter. The acid rime was neutralized by non-sea salt calcium, dissolved from particulate matter. These results suggest that the rime was not neutralized in 2002/2003, because yellow sand was not abundant in 2002/2003.View full abstractDownload PDF (5216K) -
Seiji KAMIMURA2005 Volume 67 Issue 1 Pages 33-38
Published: January 15, 2005
Released on J-STAGE: August 07, 2009
JOURNAL FREE ACCESSDownload PDF (6683K) -
in the Himalayas from a hydrodynamic viewpointKazuhisa A. CHIKITA2005 Volume 67 Issue 1 Pages 39-49
Published: January 15, 2005
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSThe expansion mechanism of glacial lakes in the Himalayas is reviewed from a hydrodynamic viewpoint. Physical conditions of three moraine-dammed lakes, Tsho Rolpa and Imja in Nepal and Lugge in Bhutan, have been explored since 1993. A valley wind blowing diurnally over the end moraine or the adjacent dead-ice zone, which lies upwind of the lakes, is similar in the daily maximum speed(3.6 to 8.6 m/s).However, the thermal and density structures of the lakes are quite different among the three lakes, indicating that wind-driven currents are strong in Tsho Rolpa, but relatively weak in the order of Lugge and Imja. The end moraine of Tsho Rolpa is almost leveled to the lake surface, while the end moraine or the dead-ice zone of Lugge and Imja is ca.20 to 30 m higher than the lake surface. The screening effect of the topography upwind of Lugge and Imja is likely to weaken the valley wind over the lakes. Meanwhile, in Tsho Rolpa and Lugge, sediment-laden underflows were produced by turbid meltwater input at the base of the cliff-shaped glacier terminus. It is suggested that the high expansion of the Tsho Rolpa basin is induced by the advective diffusion of heat based on the wind-driven, vertical water circulation which is coupled with the sediment-laden underflows. A 3D numerical simulation of airflow was conducted by making a model of realistic topography in the calculation domain, in order to verify the screening effect of the topography upwind of the lakes.When the end moraine is 20 m higher than the lake surface, the wind velocity near the lake surface decreases by 31% in comparison to a case with the end moraine leveled to the lake surface. It is concluded that the weak wind mixing in Imja resulted from the topographic screening effect coupled with the short fetch.View full abstractDownload PDF (3148K)
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