Laser Doppler anemometry (LDA) measurements in the fully developed turbulent flow through a one-sided rib-roughened square channel with a rib-height-to-channel-height ratio of
k
/
H
=
0.0667
and a ...rib-pitch-to-rib-height ratio of
p
/
k
=
9
were carried out at Reynolds numbers (based on the channel height
H
and the mean bulk velocity
u
B
) of
Re
H
=
5.0
·
10
4
and
1.0
·
10
5
. Mean velocities, Reynolds normal, and shear stresses were determined. The first- and second-order statistical moments of the velocity differed slightly between both Reynolds numbers when normalized by the bulk velocity and the channel height. Deviations were attributed to a minor elongation increase in the large recirculation region behind the rib with increasing Reynolds numbers. The crucial role of turbulent diffusion was reflected in the non-coincidence of the maximum primary mean shear and the Reynolds normal stress as well as outward drifts of the Reynolds stress peaks along the rib crest. Turbulent diffusion contributed significantly to the turbulence kinetic energy (
TKE
) budget near the rib crest and within the separated shear layer, while mean convection made a remarkable contribution only at the rib leading edge. The detailed first- and second-order moments provide a basis for the validation of computational methods and turbulence models.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, we present experimental results for a non-isothermal vertical confined backward facing step conducted with a low-Prandtl number fluid. The eutectic alloy gallium–indium–tin is used as ...the working fluid. We conducted experiments for different Reynolds and Richardson numbers covering both forced and mixed convection regimes. Time-averaged velocity profiles were measured at six streamwise positions along the test section center-plane with so-called permanent magnet probes. The local Nusselt number was measured in streamwise and spanwise directions along the heating plate mounted right after the step. We further ran RANS simulations of the experiment to study the qualitative influence of assuming a constant specific heat flux thermal boundary condition for the experiment heating plate. The measured velocity profiles show the expected behavior for both studied convection regimes, while the measured streamwise local Nusselt number profiles do not. This is explained by how the heating plate thermal boundary condition is defined. We performed an order of magnitude estimate to estimate the forced- to mixed convection transition onset. The estimate shows good agreement with the experimental data, although further measurements are needed to further validate the estimated transition threshold. The measurement of fluctuating quantities remains an open task to be addressed in future experiments, since the permanent magnet probe measurement equation needs further adjustments.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
IFMIF-DONES (International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source) is a neutron irradiation facility aiming at providing material irradiation data for the construction of ...DEMOnstration fusion power plants. This work presents nuclear analyses and associated neutronics modeling conducted on an updated design of the High Flux Test Module (HFTM) of IFMIF-DONES. Neutron fluxes, damage dose rates and gradients, gas production and nuclear heating have been calculated for the standard profile in 20 × 5 cm2 and a reduced size in 10 × 5 cm2 of the deuteron beam with 40 MeV energy and 125 mA current. The results indicate that the reduced beam can provide higher damage dose rates fulfilling the DONES requirement. On the other hand, the reduced beam size results in less irradiation uniformity, higher gas production to damage dose ratios, as well as stronger peak nuclear heating.
•Comprehensive nuclear responses on the IFMIF-DONES high flux test module have been analyzed.•Comparisons have been made between the normal deuteron beam size and the reduced beam size.•The DONES irradiation capabilities have been studied for fulfilling the requirements of DEMO construction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A lateral fluid transport contributes to the heat transfer enhancement behind the rib.•Vortex structures deteriorating heat transfer are eliminated by modified rib shapes.•Thermal performance is ...increased for ribs not extended over the total channel width.
Delayed Detached Eddy Simulations with the k-ω-SST turbulence model were conducted for 8.0 MPa pressurized helium-gas flow in cooling channels with rib arrays on one wall at a Reynolds number of Re = 1.05 × 105. Turbulent flow and heat transfer were determined for arrays of eight variously configured V-shaped and transverse ribs. The relative roughness was e/Dh = 0.0638 and 0.0652 and the rib pitch was p/e = 10. The results showed that for ribs not extended over the total channel width, form drag was reduced and flow stagnation regions with a low heat transfer at the rib corners on the sides disappeared, whereas heat transfer by forced convection increased. Compared to smooth channel flows, the Nusselt numbers were increased by a factor of 1.6–1.8 and 2.2–2.5 for the transverse and V-shaped ribs, respectively. The corresponding friction factors were enhanced by a factor of 2.4–2.9 and 2.8–3.7, respectively. Evaluation of the thermal performance of structured cooling channels in comparison with smooth cooling channels revealed that thermal performance was best for the upstream directed 60° V-shaped ribs. The results showed that secondary flow motion induced by a V-shaped rib configuration caused an outward convective fluid transport within the recirculation region behind the rib. Vortical structures associated with local heat transfer deterioration behind the rib could be eliminated by appropriate designs of rib cross sections. Both lateral convective fluid transport and the elimination of vortical structures deteriorating heat transfer were found to lead to a significant heat transfer enhancement in the leeward rib region for the V-shaped ribs with modified cross section.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This work continues the development of a numerical model to simulate transient tritium transport on the breeder zone (BZ) level for the EU helium-cooled pebble bed (HCPB) concept for DEMO. The basis ...of the model is the open-source field operation and manipulation framework, OpenFOAM. The key output quantities of the model are the tritium concentration in the purge gas and in the coolant and the tritium inventory inside the BZ structure. New model features are briefly summarized. As a first relevant application a simulation of tritium transport for a single pin out of the KIT HCPB design for DEMO is presented. A variety of scenarios investigates the impact of the permeation regime (diffusion-limited vs. surface-limited), of an additional hydrogen content of 300 Pa H2 in the purge gas, of the released species (HT vs. T2), and of the choice of species-specific rate constants (recombination constant of HT set twice as for H2 and T2). The results indicate that the released species plays a minor role for permeation. Both permeation and inventory show a considerable dependence on a possible hydrogen addition in the purge gas. An enhanced HT recombination constant reduces steel T inventories and, in the diffusion-limited case, also permeation significantly. Scenarios with 80 bar vs. 2 bar purge gas pressure indicate that purge gas volumetric flow is decisive for permeation.
In the IFMIF-DONES facility of the future, the back-plate behind the Li target will receive strong irradiation from high-energy neutrons. The potential use of the back-plate for material specimens is ...attractive with respect to providing complementary irradiation data for Eurofer. In this work, DPA (displacement per atom) and gas production rates as well as DPA gradients and temperature distributions have been studied for the center segment of the back-plate, using both a nominal beam and a reduced beam footprint. It is shown that specimens can be produced with high DPA in similar conditions to the DEMO first-wall. Based on the size of the SSTT (small specimen test technology) specimens, the limited number of samples obtainable from the adopted arrangement scheme is driven by a major constraint: the thickness of the back-plate. A parametric study of the back-plate’s thickness provides an alternative arrangement scheme; thus, the DPA and gradient of the specimens are remarkably improved.
The Helium Cooled Pebble Bed (HCPB) breeding blanket is one of the two driver-blanket candidates for the European fusion demonstration power plant (EU DEMO) within the framework of the EUROfusion ...Consortium. As the EU DEMO program is going, testing of mockups becomes increasingly important. In this article, the engineering design of a first-ever breeder zone mockup of the EU DEMO HCPB breeding blanket is reported. The mockup will be tested in the high-pressure, high temperature, helium facility (HELOKA) at Karlsruhe Institute of Technology. This mockup will act as a test rig to validate heat transfer correlations, CFD software, and thermal hydraulics systems codes. As pressure equipment, the mockup shall conform to the latest European Union Pressure Equipment Directive 2014/68/EU. The design description, rationale and test matrix, and corresponding analyses are discussed and presented.
IFMIF-DONES is a facility under construction in Granada, whose main goal is the validation and characterization of materials under a fusion prototypic irradiation field. This field is created by the ...interaction of a high energy intense continuous deuteron beam and a flowing liquid lithium target. The requirements imposed on the beam at the interaction point are a complex trade-off among the scientific experimental needs for the materials irradiation defined at the top-level requirements (20 dpa in a volume of 0.3 dm3 and 50 dpa in 0.1 dm3), and the technical constraints of several systems such as the Accelerator Systems, the Lithium Systems, and the Test Systems. Recent simulations with the initial definition of beam-on-target requirements showed the necessity of redefining them in order to fulfill the irradiation needs. This contribution will address the main challenges to gather the inputs for the definition and reassessment of the beam-on-target requirements. A comparison detailing the main changes compared to the previous ones will be given, together with a short overview of the studies ongoing by different systems to analyze the impact of each beam-on-target requirements on the performance of the whole facility.
•Fusion materials irradiation.•Deuteron accelerator.•High current accelerator.•Beam delivery system.•Beam on-target.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Helium flow within a heated mini-channels has been analysed using Helium experiments conducted in KIT.•Numerical simulations have been performed for low Reynolds number (Re=4000-10000) helium ...flows.•Four turbulence models, RSM, k-ε, k-ω SST and V2F were tested.•RSM and SST models are appropriate numerical tools for the heat transfer analysis of HFTM of the IFMIF-DONES.
Helium flow at low pressure (0.3 MPa) is used to cool the specimen capsules and the structure of the neutron irradiated High Flux Test Module (HFTM) of the IFMIF-DONES (International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source). The flow path includes mini-channels with gap-widths less than 1 mm where a high velocity low Reynolds number helium flow is used as cooling medium. The large span of Reynolds numbers from laminar to fully turbulent is a significant challenge for the simulation of the complete HFTM. Four turbulence models, the Reynolds Stress transport (RSM); the k-ε (KE) model; the k-ω Shear-Stress-Transport (SST) model and the V2F model were tested using experiments conducted in Karlsruhe Institute of Technology (KIT). Numerical simulations have been performed for low Reynolds number (Re = 4000–10000) helium flows in a heated mini-channels. The RSM model provides the best heat transfer prediction for the full range of Reynolds numbers. KE and V2F models are not suitable for the simulation of the transitional flows. The accuracy of the SST model can be increased by variation of the time scale limiter coefficient. RSM and SST turbulence models can be considered as appropriate numerical tools for the heat transfer analysis of HFTM.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Irradiation conditions for steel match the conditions anticipated for DEMO.•Accelerated testing for steel is possible in IFMIF-DONES.•Accelerated testing for tungsten and copper is possible in ...IFMIF-DONES.•Testing of tungsten is possible at up to 800 °C.
IFMIF-DONES (International Fusion Materials Irradiation Facility - DEMO-oriented Neutron Source) is currently being developed in the frame of the EUROfusion Early Neutron Source work package (WPENS), based on the results achieved in the ongoing IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project by Japan and Europe in the frame of the Braoder Approach (BA) agreement. The neutron source's limited product of “irradiation volume × neutron fluence” on one hand and the large potential test matrix (defined by number of material grades, test types, irradiation- and test temperature levels and damage dose levels) on the other hand, require a careful selection of test conditions by collaborative effort of the communities of DEMO designers, fusion materials science and the irradiation facility designers. This paper describes achievable irradiation conditions in the High Flux Test Module (HFTM) of IFMIF-DONES, characterized by levels and gradients of irradiation temperatures and nuclear responses (dpa, H and He production). The HFTM development focuses on 9%-Cr Reduced Activation Ferritic Martensitic steel irradiations, but also the possibilities of tungsten and copper alloy irradiations are explored. Possible specimen arrangements and issues of the Small Specimens Test Technique are also discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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