Thermal And Hydraulic Analysis Of The Vacuum Vessel Thermal Shield


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ITER Team (Garching, Germany) - International Thermonuclear Experimental Reactor


The presented analysis is aimed (a) to evaluate temperature state of the VVTS, (b) to define VVTS cooling system parameters, (c) to estimate the heat absorbed by VVTS coolant and (d) heat influx to TFC structures for both Normal Operation NOC and baking conditions (VV baking).
To accomplish this task 2D thermal analysis of the some typical VVTS panel cross-sections has been carried out.

The results of the performed thermal analysis allow us to draw the following conclusions:

1. The main part of radiation heat flux from the VV (QGHe ~160 kW) is intercepted by the VVTS cooling system. And only a small portion of the total heat radiated from the VV {QTFC < 0.6 kW Ю[(0.4 kW(outer VVTS)+0.2 kW(inner VVTS)]} reaches the TFC surface. At this, the obtained thermal-hydraulic parameters of the VVTS cooling system are within the specified range (flow velocity 10 m/s, GHe heat up < 30 K, pressure drop Ј 0.05 MPa.). Therefore, it can be concluded that the present design of GHe cooling system is applicable.

2. The averaged value of heat flux on the TFC is less than specified limit (1W/m2) at the given GHe parameters. At the same time, the values of heat load onto the TFC in some places slightly exceeds the specified q » 1 W/m2 at VV baking regime:

q » 1.4 W/m2 for inner panel (cross-section C-C, pitch - 500 mm);
q » 1.1 W/m2 for outer panel (cross-section D-D, pitch - 650 mm).

3. In order to keep maximal heat flux on the TFC within the specified limit of 1 W/m2 it is necessary to increase GHe velocity up to 25 m/s that resulting in rising of the GHe flow rate in 2.5 times and hydraulic losses in cooling tubes up to 0.08 MPa. These thermo-hydraulic parameters are some above the specified limits and can be used for the evaluation of the cooling system performance only.

4. Results of the calculation of the chess assembly design show, that in area of outlet cross-section of inner panel heat onto the TFC is equal to q » 1.95 W/m2. That is why the support structure is least suitable from thermal point of view



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