Page 179 - Fundamentals of Magnetic Thermonuclear Reactor Design

160 Fundamentals of Magnetic Thermonuclear Reactor Design

cables and other conducting structures. For the purpose of the model validation,
simulated data were compared with experimental results.

A.5.1.2.1 Central Solenoid Model Coil
A detailed thermal–hydraulic model of CSMC is a combination of the following
three local computational models:
1. A 1D model used to simulate transient behaviour of helium flows in differ-
ent pipes and channels, including cooling channels of the superconducting
cables of the inner and outer modules, the CSCI, two SHe heat exchangers,
the upper and the lower support structures, the base and auxiliary cryogenic
systems. The total number of channels modelled is above 160. Each of the
36 CIC SCs is modelled separately, with regard for two non-equilibrium
helium flows (in the spiral type central channel and in the bundle channel).
Transverse heat and mass transfer between these flows occurs through the
gaps of the spiral.
2. A 2D model utilising the finite difference approximation for the CSMC cross-
sections and intended to accurately simulate the non-stationary transverse heat
conduction between different turns/layers of the CSMC. Here thermal links
occur between turns and with the upper and the lower support structures. The
model uses the cylindrical coordinate system. A 2D rectangular mesh for five
cross-sections has over 450,000 nodes. The 2D solid model is linked with the
1D flow model via relevant boundary conditions at the wetted perimeter of the
bundle channel to form a single quasi-3D CSMC model.
3. A 2D model describing transient AC losses in the CSMC and CSCI cables
using field maps for different time points of the experiment scenario.

In the CSMC model, the cooling circuit consists of six parallel branches,
each equipped with inlet and outlet control valves. The model also includes a
circulation pump, two SHe heat exchangers (HXP1 and HXP2) and two cryo-
lines (Fig. A.5.1).
The test program involved a series of current pulses with amplitudes in-
creasing from 5 to 46 kA. Pulses with amplitudes of 30, 40, 43 and 46 kA
were taken as a reference. All pulses of a trapezoidal shape were spaced by
∼3000 s.
These operating conditions, as well as individual hydraulic characteristics
of the 36 SCs and six control valves [22], were implemented in the simulations
with the quasi-3D CSMC model. An overview of simulation results as com-
pared to experimental observations is presented next.

A.5.1.2.2 Simulations Versus Experiments
Results obtained with the computational model of CSMC were validated against
data obtained in experiments where a non-stationary increase of SHe pressure/