Multi-solid multi-channel Mithrandir (M3) code for thermal–hydraulic modelling of ITER Cable-in-Conduit Superconductors

Dipartimento di Energetica, Politecnico, Duca degli abruzzi 24, 10129 Torino, Italy
Fusion Engineering and Design (Impact Factor: 1.15). 10/2007; 82(5):1607-1613. DOI: 10.1016/j.fusengdes.2007.04.035


We present a new multi-solid multi-channel (M3) thermal–hydraulic model for the analysis of the International Thermonuclear Experimental Reactor (ITER) Cable-In-Conduit Conductors (CICC). The model discretizes the cross section of an ITER CICC into M current carrying cable elements (e.g., the six last-but-one cabling stages—the petals), coupled with N hydraulic channels (e.g., the six petals + the central channel) and K non-current carrying solid components (e.g., the jacket of the CICC), with M, N and K arbitrary integers. Along each of the M + K solid components a 1D transient heat conduction equation is solved, whereas along each of the N channels three Euler-like 1D equations, derived from the conservation laws for compressible He flow, are solved. The resulting quasi 3D model, in which 1D equations are coupled by heat and mass transfer between the different CICC components, is implemented in the M3 code and validated against experimental results from the ITER Good Joint sample and the ITER Poloidal Field Conductor Insert Full Size Joint Sample. The new code is able to reproduce with good accuracy the measured temperature gradients on the CICC cross section, provided sufficiently accurate input data are available.

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    • "While the PFCI test concentrated on DC performance (current sharing temperature and critical current measurements) and AC loss measurements, which were recently analysed in some detail [4], a fraction of the test campaign was devoted to stability and quench propagation measurements, which were not addressed by analysis so far. The 1-D Mithrandir code [5], already validated against stability and quench data from previous Nb3Sn Insert Coils [6]–[8] as well as against quench data from ITER sub-size conductors [9], and the quasi-3D M3 code [10], implementing a more detailed thermal-hydraulic description of the CICC cross section, are used here to analyse the issues of quench propagation in the PFCI. "
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    ABSTRACT: We analyse the issues of quench propagation in the NbTi Poloidal Field Conductor Insert (PFCI), recently tested at JAEA Naka, Japan. The simulation tools Mithrandir, already validated against data from previous Nb3Sn Insert Coils, and M3, implementing a more detailed thermal-hydraulic description of the CICC cross section, are used. The results of the analysis are reported in the paper and compared with experimental data, with particular attention to NbTi versus Nb3Sn features and to the effects of different model assumptions.
    IEEE Transactions on Applied Superconductivity 07/2010; 20(3-20):491 - 494. DOI:10.1109/TASC.2010.2041547 · 1.24 Impact Factor
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    • "As the CICC axial/transverse size ratio is typically P10 3 in a coil, 1D (axial) models [2], or combinations thereof [3] [4] to approximately treat the actually multi-dimensional situation, are customarily used for the sake of sparing CPU time, but they require constitutive relations for the transverse fluxes, including friction factors and heat transfer coefficients. Unfortunately, however, the wide database available at present on, e.g., friction factors, is neither fully comprehensive nor free of contradictions/ambiguities [5] [6] [7]. "
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    ABSTRACT: Dual-channel cable-in-conduit conductors (CICC) are used in the superconducting magnets for the International Thermonuclear Experimental Reactor (ITER). As the CICC axial/transverse size ratio is typically ∼1000, 1D axial models are customarily used for the CICC, but they require constitutive relations for the transverse fluxes. A novel approach, based on Computational Fluid Dynamics (CFD), was recently proposed by these authors to understand the complex transverse thermal–hydraulic processes in an ITER CICC from first principles. Multidimensional (2D, 3D) Reynolds-Averaged Navier–Stokes models implemented in the commercial CFD code FLUENT were validated against compact heat exchanger and ITER-relevant experimental data, and applied to compute the friction factor and the heat transfer coefficient in fully turbulent spiral rib-roughened pipes, mimicking the central channel of an ITER CICC. That analysis is extended here to the problem of heat and mass transfer through the perforated spiral separating the central channel from the cable bundle region, by combining the previously developed central channel model with a porous medium model for the cable region. The resulting 2D model is used to analyze several key features of the transport processes occurring between the two regions including the relation between transverse mass transfer and transverse pressure drop, the influence of transverse mass transfer on axial pressure drop, and the heat transfer coefficient between central channel and annular cable bundle region.
    Cryogenics 03/2010; 50(3-50):158-166. DOI:10.1016/j.cryogenics.2009.11.005 · 1.17 Impact Factor
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    • "One of the test issues so far is how the current distribution in the cable may affect the results in a way peculiar to the SULTAN configuration rather than to the coil; in turn, this current distribution is increasingly related to the temperature distribution inside the cable, as the quench is approached. The THELMA code is best suited to study this coupled problem, as it combines an electromagnetic model of the cable [3], including a detailed description of the jacket [4], with a multi-solid multi-channel thermal-hydraulic model of the CICC [5]. THELMA was validated for several types of transients and superconducting materials in short samples Manuscript received August 23, 2008. "
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    ABSTRACT: The THELMA code is used to study the coupled thermal-hydraulic electro-magnetic problem of the current and temperature distribution inside the TFPRO2 Nb<sub>3</sub>Sn SULTAN sample, which was tested in 2007. The code computes self-consistent voltage and temperature values both on the jacket, where they are measured, and inside the cable, where they are more directly representative of the conductor performance. The measured temperature gradients, related to non-uniform Joule heating at the joint and in the high-field region, as well as to non uniform current distribution, are reasonably well reproduced by the model, together with the voltage-current characteristics.
    IEEE Transactions on Applied Superconductivity 07/2009; 19(3-19):1483 - 1487. DOI:10.1109/TASC.2009.2018205 · 1.24 Impact Factor
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