2002 Fiscal Year Final Research Report Summary
Modeling of Marangoni Convection Induced at Lithium Bromide Aqueous Solution's Surface and its Application to Improve Absorbers Performance
| Project/Area Number |
13650234
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | Osaka City University |
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Principal Investigator |
NISHIMURA Nobuya Osaka City Univ., Faculty of Eng., Associate Professor, 大学院・工学研究科, 助教授 (30189310)
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| Co-Investigator(Kenkyū-buntansha) |
UEDONO Norio Osaka Gas Co. Ltd., Commercial and Industrial Market Development Department, Senior Engineer, エネルギー開発部(常勤研究職), シニアエンジニア技術主幹
IYOTA Hiroyuki Osaka City Univ., Faculty of Eng., Research Associate, 大学院・工学研究科, 助手 (10264798)
NOMURA Tomohiro Osaka City Univ., Faculty of Eng., Professor, 大学院・工学研究科, 教授 (50164736)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Absorption Enhancement / Surfactant / Marangoni Convection / Absorber / Laser Holography / Temperature Measurement / Diflusion Coefficient / Absorption Refrigerator |
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| Research Abstract |
The absorption refrigerators are drawing great attention as a CFCs-free refrigerator friendly to the global environment. And authors have been revealed the refrigerating performance increases to double with addition of surfactant into the LiBr aqueous solution. But detailed mechanisms of the surfactant's absorption enhancement effect have not been clarified yet.
Therefore, in the study, effects of an addition of surfactant to a lithium bromide aqueous sohticn have been investigated experimentally for both thin stagnant pool and falling liquid film of LiBr aqueous solution. N-octanol and 2 ethyl-hexanol were used as surfactants.
The Marangoni convection occurred at/beneath the solution surface in the very beginning of steam absciption was observed both by a real-time type laser holographic visualization and by temperature measurements with extremely fine gauge thermocouples. Generation and growth of the Marangoni convection were both observed and evaluated quantitatively by the flow visua
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lization. Furthermore, solution's surface temperatures with and withoutaddition of the surfactant were measured minutely. Cell's formation pattern and migration speed at the surface were measured varying the initial surfactant's concentration ranging from 0 to 50000ppm and the shallow liquid layer thickness ranging from 2 to 5mm. And spacio-temporal scales of the Marangoni convection were determined. Also solution temperature changes at the surface were compared. Temperature increases when the surfactant was added to its solubility limit became almost double than that case of no surfactant. From these temperature differences, effects of the surfactant on absorber's performances were estimated by a calculation quantitatively with diffusion coefficient as an evaluation value.
Furthermore, effects of the surfactant (n-octanol) on performances of the vertical flat plate absorber have been investigated. Refrigerating capacity increases with increase of the surfactant concentration. In case of the surfactant concenlration is 100ppm, the refrigerating capacity become larger about 3 to 4 times than that case of no surfactant. Less
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