Effects of RANS-Type turbulence models on the convective heat loss computed by CFD in the solar two power tower

The effect of the choice of Reynolds-Averaged Navier-Stokes (RANS) type turbulence closure on the Computational Fluid Dynamics (CFD) prediction of convective heat losses from the Solar Two central receiver is considered in this paper for a simplified receiver geometry approximated by flat panels. Computed convective losses at steady state are ~ 2-3% (1%) of the total power absorbed by the receiver, at high (low) wind speed, depending on the turbulence model chosen. The simulation results are consistent with those of available correlations for rough cylinders, if the macroscopic roughness due to the panel edges is accounted for, as well as with the low speed experimental results, within the respective error bars

MODELING COMPLEX SUPERCONDUCTING MAGNET SYSTEMS WITH THE 4C CODE

In the recent years, the Cryogenic Circuit Conductor and Coil (4C) code has been developed to allow the thermal-hydraulic modeling of superconducting magnets and their cryogenic circuit in the frame of nuclear fusion devices. The code consists of different modules, describing the SC winding, the structures, their cooling paths and the external SHe cryogenic circuit, respectively. 4C was successfully applied to model different kinds of transients on different magnet systems, with time scales spanning from week-long cool-down to very fast current dump, and with space scales ranging from the whole magnet to a portion of a single conductor. In this paper the main aspects of the 4C are presented, with particular emphasis on its capability to capture the main features of the magnet systems of International Thermonuclear Experimental Reactor (ITER

Multi-scale approach and role of validation in the thermal-hydraulic modelling of the ITER superconducting magnets

The ITER superconducting (SC) magnets require the forced flow of supercritical He (SHe) at ~ 4.5 K and ~ 0.5 MPa, giving thermal-hydraulics (TH) a key role in the multi-physics arena of SC magnets. Here we introduce a multi-scale approach to the TH modelling of ITER magnets, based on the fact that the TH relevant space scales range from the 10-100 m of magnet size/Cable-In-Conduit Conductors (CICC) length, down to the 10-2 m of the transverse size of a CICC, while the relevant TH time scales also cover several orders of magnitude. On the "macro-scale", the entire system (winding + structures + cryogenic circuit) is considered; this requires the treatment of the "meso-scale", where single CICC are treated, weakly thermally coupled inside a winding as needed. The constitutive relations needed by the 1D meso-scale models, i.e., friction factors and heat transfer coefficients, may in turn be derived analyzing a limited portion of the CICC on the "micro-scale", with detailed 2D-3D Computational thermal-Fluid-Dynamics (CtFD) models. At each scale, the different issues related to code development, benchmarking/validation and application are considered in the paper. The choice of developing a code in-house is compared to the commercial codes and/or freeware. The reciprocal benefits obtained from these codes by the ITER magnet R&D program (which led, e.g., to the realization and test of Model and Insert coils, as well as many short samples), and vice versa, are discussed. Several examples of the multi-scale approach to the TH modelling of SC magnets will be presented in the paper, based on the experience developed during the last 15 years within our group, in collaboration with laboratories in the EU, Japan, Russia, South Korea, and the US. It is argued that the intrinsic modularity of the multi-scale approach leads to significant benefits. It is also argued that the effort towards verification&validation of the existing TH models of the ITER SC magnets has been rather limited so far, sometimes notwithstanding the existence of a significant experimental database; therefore it is recommended to launch a systematic initiative in that direction, with particular attention to the assessment of the predictive capabilities of the existing TH codes. While these capabilities are going to be more and more relevant for the ITER nuclear device, for operation and safety studies in particular, there is at this time hardly any evidence of such predictive capabilities in the published literatur

Inductively driven transients in the CS Insert Coil (II): quench tests and analysis

ABSTRACT The CS Insert Coil (CSIC), a well-instrumented 140 m long Nb 3 Sn solenoid wound one-in-hand and installed in the bore of the CS Model Coil, was tested during the summer of 2000 at JAERI Naka, Japan, within the framework of the International Thermonuclear Experimental Reactor large project