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A numerical model implemented in the open-source finite-element method FreeFEM program is presented, with the aim of introducing students to the calculation of AC losses in superconductors. With this simple approach, students can learn about the critical state model used to describe the macroscopic electromagnetic behavior of superconductors and the importance of different factors influencing the AC losses of superconductors. [ABSTRACT FROM AUTHOR]

Highlights: [•] A global, predictive picture of the ITER HTS current lead is not yet available. [•] A predictive 1-D, steady state thermal-hydraulic analysis of the full length HTS current leads has been performed. [•] For the heat exchanger, correlations previously derived by the same authors have been used. [•] The results have been compared with the ITER relevant requirements. [•] According to our results, the ITER HTS current leads will fulfill the requirements. [ABSTRACT FROM AUTHOR]

Highlights: [•] The laminar regime in the meander flow geometry has been analysed with a previously validated computational strategy. [•] Several meander flow geometries as well as flow conditions have been analysed. [•] A range for the Reynolds number has been defined in which the flow can be considered laminar. [•] Correlations for the pressure drop and the heat transfer coefficients in the laminar regime have been derived. [•] A comparison between the computed the experimental pressure drop of the W7-X HTS current lead prototype is presented. [Copyright &y& Elsevier]

Abstract: The Karlsruhe Institute of Technology is responsible for the design, construction and testing of the high temperature superconductor (HTS) current leads for the Wendelstein 7-X stellarator and for the JT-60SA tokamak. These HTS current leads mount a heat exchanger of the meander-flow type, in which the helium flows between the fins and is forced to cross flow with respect to the central Cu bar, which actually carries the current. Since an important issue in the operation of the HTS current lead is the optimization of the cooling power consumption, the helium thermal–hydraulics in such complex geometry becomes rather important. In this paper we extend a computational thermal fluid dynamics (CtFD) technique, previously introduced by the same authors and validated on short samples of meander flow heat exchanger and on the W7-X HTS current lead prototype, to a systematic analysis of the helium thermal-fluid dynamics inside different meander flow geometries. The first aim is to clarify under what operative conditions the flow regime can be considered turbulent and how the pressure drop as well as the heat transfer are related to the geometrical parameters and to the flow conditions. From the results of this analysis, correlations for the pressure drop and the heat transfer in the meander flow geometry have also been derived, which are applicable with good accuracy for the design of HXs over a broad range of geometries. [Copyright &y& Elsevier]

Abstract: This paper compares two Computational Fluid Dynamic (CFD) approaches for the analysis of flow boiling inside the first wall (FW) of the International Thermonuclear Experimental Reactor (ITER): (1) the Rohsenow model for nucleate boiling, seamlessly switching to the Volume of Fluid (VOF) approach for film boiling, as available in the commercial CFD code STAR-CCM+, (2) the Bergles–Rohsenow (BR) model, for which we developed a User Defined Function (UDF), implemented in the commercial code FLUENT. The physics of both models is described, and the results with different inlet conditions and heating levels are compared with experimental results obtained at the Efremov Institute, Russia. The performance of both models is compared in terms of accuracy and computational cost. [Copyright &y& Elsevier]

In this paper we extend the recently developed CtFD strategy for the analysis of the thermal-hydraulics of a meander flow type heat exchanger, validated against the Wendelstein7-X (W7-X) High Temperature Superconductor (HTS) current lead prototype experiment, to the case of a heat exchanger for a 68 kA HTS current lead. We aim to assess the optimized operative conditions and the influence of different geometrical configurations on the performance of the heat exchanger. [ABSTRACT FROM PUBLISHER]

Abstract: The Karlsruhe Institute of Technology (KIT) is responsible for the design, construction and testing of the high temperature superconductor current leads for the Wendelstein 7-X (W7-X) stellarator. Two prototypes of the W7-X current lead, using a meander-flow heat exchanger, have been tested in 2010 at KIT. Following an approach originally developed and applied to a sub-size mock-up heat exchanger, the Computational Fluid Dynamics code StarCD is used here for the 3D thermal-hydraulic analysis of the heat exchanger in the prototypes. The resulting friction and Nusselt parameters are then fed to a global 1D model of the current lead and the results compared to the measured pressure drop and temperature profiles along the heat exchanger. [Copyright &y& Elsevier]

We apply a recently proposed Computational thermal Fluid Dynamics (CtFD) strategy to the analysis of a meander-flow path (MF) fin-type heat exchanger (HX), to be used in the HTS current leads for the LTS coils of both the W7-X stellarator and the JT-60SA tokamak. A mock-up of the HX was tested at the Karlsruhe Institute of Technology providing the database for the validation of the computational model. The hydraulic characterization of the mock-up is considered first, and then the heat transfer characteristic is analyzed. [ABSTRACT FROM AUTHOR]