TopPageTopics 2002 > 2002-9


2008/04/08(Tue) 11:19

Control of Thermal Convection of Water by Strong Gradient Magnetic Fields

磁気浮上を物質合成へ応用する研究の一環として,勾配強磁場中における水の熱輸送を感熱液晶シートにより可視化して観察を行った.磁気浮上相当の勾配磁場B(dB/dz)=1360 T2 m-1(磁場中心;19.8T)では,わずかに残留熱対流が存在することが確認された(a).磁場を強くして2880 T2 m-1(磁場中心;26T)になったとき,ほぼ完全に対流のない熱伝導の状態が観察された(b).さらに同じ勾配磁場下で温度を40-45℃にすると,下方への磁気対流が発生することを見出した(c).この挙動は水の磁化率の温度依存性に起因している.

東北大学 金属材料研究所:茂木 巖,梅木千巧,高橋弘紀,渡辺和雄

Heat transfer in water was visually observed using a liquid-crystal sheet with thermochromism under strong gradient magnetic fields. Upward thermal convection was significantly suppressed by the magnetic force, however, it remained to a small extent even under magnetic levitation conditions with a gradient field of B(dB/dz)=1360 T2 m-1 (19.8T at the magnet center) (a). A thermal conduction state without convection was realized under a stronger gradient field of 2880 T2 m-1 (26T at the center) at 35-40シC (b), and surprisingly the downward magnetic convection was observed under the same field at 40-45シC (c). The temperature dependence of the magnetic susceptibility of water is responsible for this convection behavior.

IMR, Tohoku University: I. Mogi, C. Umeki, K. Takahashi, K. Watanabe
Reference: I. Mogi, C. Umeki, K. Takahashi, S. Awaji, K. Watanabe and M. Motokawa,
"Control of thermal convection in water by strong gradient magnetic fields", Jpn. J. Appl. Phys. 42 (2003) L715.