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TECHNICAL PAPERS: Natural and Mixed Convection

Enhanced Convection or Quasi-Conduction States Measured in a Super-Conducting Magnet for Air in a Vertical Cylindrical Enclosure Heated From Below and Cooled From Above in a Gravity Field

[+] Author and Article Information
Syou Maki

Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga Koen 6-1 Kasuga 816-8580, Fukuoka, Japan

Toshio Tagawa, Hiroyuki Ozoe

Institute of Advanced Material Study, Kyushu University, Kasuga Koen 6-1, Kasuga 816-8580, Fukuoka, Japan

J. Heat Transfer 124(4), 667-673 (Jul 16, 2002) (7 pages) doi:10.1115/1.1482082 History: Received September 24, 2001; Revised March 20, 2002; Online July 16, 2002
Copyright © 2002 by ASME
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References

Figures

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Schematic view of the experimental apparatus located in the bore of a super-conducting magnet. ① Cylindrical enclosure; ② Cooled copper plate; ③ Heated copper plate; ④ Electric heater; ⑤ Magnetic coil; ⑥ Duct of running water; ⑦ Bundle of tubes.
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Master plot for estimation of heat loss for the experiments in an enclosure heated from below and cooled from above. The solid line is obtained from conduction experiment with the enclosure placed upside-down. The dashed line is heat loss obtained from a conduction curve and will be employed for net heat flux in convection experiments. (1) (2) (3) (4) (5) zb[mm]66 66 66 66 −66 bz(∂bz/∂z) [T2/m]138 49.7 5.52 0 −138
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Summary of experimental results. Solid line is from Silveston’s experiment 4. (1) zb=+66 mm andbz(∂bz/∂z)=138 T2/m(2) zb=+66 mm andbz(∂bz/∂z)=49.7 T2/m(3) zb=+66 mm andbz(∂bz/∂z)=5.52 T2/m(4) bz(∂bz/∂z)=0 T2/m(5) zb=−66 mm andbz(∂bz/∂z)=−138 T2/m
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Average Nusselt number plotted versus magnetic Rayleigh number Ram with the data by Silveston 4. (1) Exp., bz(∂bz/∂z)=138 T2/m. (2) Exp., bz(∂bz/∂z)=49.7 T2/m. (3) Exp., bz(∂bz/∂z)=5.5 T2/m. (4) Exp., bz(∂bz/∂z)=0 T2/m. (5) Cal., Asp=6,zb=55 mm,Ra=2100 and 7000, Ram=4190 and 13970.
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Computed isotherms and velocity vectors for a cylinder of an aspect ratio=6,Pr=0.7 and (a) Ra=2100 and (b) Ra=7000. (i) Top view of isotherms at γ=0 and Z=0.5. (ii) Vertical side view of isotherms for cases (1) to (6). These cases correspond to those listed in Tables 3 and 4.
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Transient responses of the computed average Nusselt number for an enclosure of aspect ratio=6,Pr=0.7 and Ra=2100. Numbers (1) to (6) correspond to those in Tables 3, 4, and Fig. 9.
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Computed isotherms and velocity vectors for a cylinder of aspect ratio=3,Pr=0.7 and Ra=7000 with 213 grids. (1) γ=0, (2) zb=−25 mm,γ=292, (3) zb=−55 mm,γ=350, (4) zb=−95 mm,γ=1169. (a) Top view of isotherms at Z=0.5. (b) Vertical side view of isotherm. (c) Vertical side view of velocity vectors.
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Sample of the magnetizing force vectors for an enclosure 20 mm high and 60 mm in diameter in the bore of 100 mm in diameter with a coil 180 mm in diameter. (i) zb=−25 mm,γ=292 (ii) zb=−55 mm,γ=350 (iii) zb=−95 mm,γ=1169 (a) γ∇⃗B2, (b) γ∇⃗B2+(0,0,1)T
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Modeled location of enclosure at zb=95, 55, 25, −25, −55, and −95 mm in the bore of 100 mm in diameter with a modeled magnetic coil: (a) magnetic induction vectors B⃗; and (b) magnetizing force vectors ∇⃗B2.
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Modeled vertical cylinder with computational grid lines for an enclosure with aspect ratio=6: (a) top view, and (b) vertical side view.

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