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| | výběr: kategorie NUTHOS| nalezeno záznamů: 4 | |
| [1] | Experimental Study on Boiling Heat Transfer using Standard Nanofluids| Y.J. Choo, S.Y. Chun, J.K. Park, C.H. Song, I.C. Bang | | Korea Atomic Energy Research Institute, Tokyo Institute of Technology | | The cooling performance of nanofluid was investigated in the rapid quenching experiments using a thin platinum wire heater and the effect of surface modification by nanoparticle-deposition on a wire heater on cooling characteristics was examined also. Water-based silicon nanofluids (vol 0.01% and 0.001%) were prepared by the Pulsed- Laser Ablation in Liquid technique (PLAL). Throughout the whole cooling process, the transition of wire temperature was measured by data acquisition system and the boiling characteristics were observed by a high-speed camera. Based on the cooling rates and reconstructed boiling curves, meaningful difference in the characteristics of the boiling heat transfer between the water and the silicon nanofluids cannot be identified during a quenching. On the other hand, when the silicon nanoparticle-coated wire is quenched with water, a very high cooling rate is observed and a considerably large heat transfer coefficient is obtained in the nucleate and the transition boiling regions. | kategorie:NUTHOSpublikováno:NUTHOS-7, 5-9 October 2008, Seoul, Korea - No.145 | | umístění:| Tomáš Vytiska | | | | | | | |
| [2] | Experimental Study of Pool Boiling CHF Enhancement by Multi-scale Surface Modification| Seontae Kim, Hyungmo Kim, Ho Seon Ahn, Hangjin Jo, Joonwon Kim, Moo Hwan Kim | | Department of Mechanical Engineering, POSTECH | | This study investigates the influence of artificially modified multi-scale structures on pool boiling critical heat flux (CHF). Nanofluid CHF experiments have shown that the deposition of nanoparticles on heater surfaces during pool boiling enormously enhances the CHF. The metal-oxide nanoparticle-deposited surfaces are highly wettable and have a fractal multi-scale structure that promotes capillary wicking. In this study, we tried to reproduce the CHF enhancement of the nanofluid experiments by surface modification with high wettability and liquid spreading on micro/nano multi-scaled structure using micro-electromechanical systems fabrication techniques. The results reveal the contributions to CHF enhancement of wetting and multi-scale surface structure, as well as their combined effects. | kategorie:NUTHOSpublikováno:NUTHOS-7, 5-9 October 2008, Seoul, Korea - No.185 | | umístění:| Tomáš Vytiska | | | | | | | |
| [3] | Subcooled Flow Boiling Heat Transfer of Dilute Alumina, Zinc Oxide, and Diamond Nanofluids at Atmospheric Pressure| Sung Joong Kim, Tom McKrell, Jacopo Buongiorno, Lin-wen Hu | | Nuclear Science and Engineering Department, MIT | | A nanofluid is a colloidal suspension of nano-scale particles in water, or other base fluids. Previous pool boiling studies have shown that nanofluids can improve the critical heat flux (CHF) by as much as 200%. In this study, subcooled flow boiling heat transfer and CHF experiments were performed with low concentrations of alumina, zinc oxide, and diamond nanoparticles in water (< 0.1 % by volume) at atmospheric pressure. The nanofluid tests revealed a substantial CHF enhancement (40-50%) at the highest mass flux (G=2500 kg/m2·s) and concentration (0.1 %vol.) for all nanoparticle materials. This paper focuses on reporting the flow boiling heat transfer data. It was found that for comparable test conditions the values of the nanofluid and water heat transfer coefficient are similar (within ±20%). The heat transfer coefficient increased with mass flux and heat flux for water and nanofluids alike, as expected in flow boiling. Also, the traditional boiling heat transfer correlation by Chen could not reproduce our water and nanofluids data well. | kategorie:NUTHOSpublikováno:NUTHOS-7, 5-9 October 2008, Seoul, Korea - No.210 | | umístění:| Tomáš Vytiska | | | | | | | |
| [4] | An Axiomatic Design Approach of Nanofluid-Engineered Nuclear Safety Features for Generation III+ Reactors| In Cheol Bang, Gyunyoung Heo, Young Hoon Jeong, Sun Heo | | Tokyo Institute of Technology, Kyung Hee University, KAIST, Korea Hydro and Nuclear Power Co. | | A variety of Generation III/III+ reactor designs featured by enhanced safety and improved economics are being proposed by the nuclear power industries around the world to solve the future energy supply shortfall. Nanofluids coolants showing the improved thermal performance are being considered as a new key technology to secure the nuclear safety and economics more tightly. However, it should be noted that there would be lack of comprehensible design works to apply nanofluids to Generation III+ reactor designs, though. In this work, the review for accident scenarios under considering expected nanofluid mechanisms is carried out to seek the detailed application spots. The Axiomatic Design (AD) theory is, then, applied to systemize the design of nanofluid-engineered nuclear safety systems such as Emergency Core Cooling System (ECCS) and External Reactor Vessel Cooling System (ERVCS). The various couplings between Gen-III/III+ nuclear safety features currently being proposed and nanofluids with unique characteristics are investigated and tried to be reduced from the perspective of AD in terms of prevention/mitigation of severe accident. This study contributes to establishment of the standard communication protocol in the design of nanofluid-engineered nuclear safety systems. | kategorie:NUTHOSpublikováno:NUTHOS-7, 5-9 October 2008, Seoul, Korea - No.238 | | umístění:| Tomáš Vytiska | | | | | | | |
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