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FUSION HIGH POWER DENSITY COMPONENTS AND SYSTEM and HEAT REMOVAL AND PLASMA-MATERIALS INTERACTIONS FOR FUSION Inn on the Alameda, Nov. 15-17, 2006. Heat Transfer performance for high Prandtl and high temperature molten salt flow in sphere-packed pipes. Tomoaki Satoh 1 , Kazuhisa Yuki 1 ,
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HEAT REMOVAL AND PLASMA-MATERIALS INTERACTIONS
Inn on the Alameda, Nov. 15-17, 2006
Tomoaki Satoh1, Kazuhisa Yuki1,
Hidetoshi Hashizume1, Akio Sagara2
1 Advanced Fusion Reactor Eng. Lab.
Dept. of Quantum Science and Energy Eng.,Tohoku University, Japan
2 National Institute for Fusion Science, Japan
D-T Fusion Reaction
D(2H)+T(3H) →4He + n + 17.06MeV
Roles of a blanket in a fusion reactor
Fig. 1. 3D view of FFHR
In the design of a force-free helical reactor (FFHR),
molten salt Flibe (LiF : BeF2 = 66 : 34) is recommended
as a blanket material..
It is necessary to enhance heat transfer performance
with relatively low flow velocity.
To investigate heat transfer performance of Flibe, Tohoku-NIFS Thermofluid loop (TNT loop) was built in 1998.
Fig. 1 Tohoku-NIFS Thermofluid loop
Fig.2 Temperature dependance of Pr1. Background1-3. Features of HTS
Flibe contains toxic Be ⇒ Using alternative molten salt, HTS
Comparison of features
between Flibe and HTS
Flibe (LiF - BeF2 : 66 - 34)
Melting point : 459 C
Pr : 35.6 @500 C
Difficult to treat
HTS (KNO3,NaNO2,NaNO3 : 53-40-7)
Melting point : 142 C
Pr :27.7 @200C
No toxic substances
TNT loop was modified.
Entrance region : nearly 50D
Direct electrical heating method
Fig. 5 Tohoku-NIFS Thermofluid loop
Aim of this study
(b) Modified test section
(a) Previous test section
Fig. 6 Comparison between modified test section and previous test section
T.C. for measuring inlet bulk temp.
T.C. for measuring outlet bulk temp.
Entrance region : 30D
To alleviate an effect of thermal stress2. Experimental2-1. Experimental apparatus
Length to develop boundary layer : lv
lv = 0.693 × Re0.25 × D
( Re : Reynolds number, D : Inner tube diameter )
When Re = 15000,
lv= 0.693 × 150000.25 × D ≈ 8D<< Entrance region
Fig.7Schematic view of the modified section
Fig. 8 Observations of test-section inner surfaces
HTS is thermally decomposed above 450C. Main reaction is as follows,
The present study is carried out under the condition of
HTS temperature up to 350C. ⇒ No chemical deposition
No effect for heat transfer experiment.
Entrance3. Results and Discussion3-2. Heat transfer of circular pipe (CP)
Tin=200 [°C], Pr ≈ 27
Thermal boundary layer is fully developed from 500 mm position.
Temperatures measured in this region are used for evaluating heat transfer performance.
Fig. 9 Typical temperature profile
along the test section
Modified Hausen equation
Fig. 10 Comparison between acquired Nu and the empirical Eqs.
Good agreement with above Eqs.
Maximum error : 10%
Modified Petukhov equation
(104 ≤ Re ≤ 5x106, 0.5 ≤ Pr ≤ 2000)
Also good agreement with above Eq.
Maximum error : 15%
Fig. 11 Comparison between acquired heat transfer coefficient and the modified Petukhov Eq.
Heat transfer correlations for general fluid in CP can be used to evaluate heat transfer characteristics for high temp. molten salt.
Manglik equation for swerl tube
4 times higher
Fand equation for SPP
m = 0.25, n = 1, p = 0.4054, q = 0.5260, r = -0.6511.
Fig. 12 Results of the heat transfer with packed bed under same velocity condition.
In the case of using D/2 spheres, pressure drop gives good agreements with drag model. (by M. OKUMURA et. al)
Evaluating pumping power of SPP
Fig. 12 Results of the heat transfer with packed bed under same pumping power.
Allowable temperature of structural material
Outlet temp. can be raised to 650C.
Other coolant is necessary for first wall cooling.
(or should we change the composition of Flibe to decrease melting temperature ?)