Search results for "fluid"
showing 10 items of 5513 documents
An enhanced, near-term HCPB design as driver blanket for the EU DEMO
2019
The Helium Cooled Pebble Bed (HCPB) breeding blanket is a candidate as driver blanket for the EU DEMO. The reference design of the HCPB is based on a cooling plate “sandwich” arrangement built in Multi-Module Segments. This architecture significantly improved the tritium breeding performance (TBR = 1.15) and the plant circulating power (≈130 MW) compared to the former ITER-like “beer-box”-like design (TBR<1.10, plant circulating power>200 MW). However, several issues remain with this design, in which (1) the still large power required per He circulator (beyond the state-of-the-art for these components) and (2) the large tritium inventory foreseen in Be have been identified as the most…
Flow and Heat Transfer in Corrugated Passages: Direct and Large Eddy Simulation and Comparison with Experimental Results
1993
Direct and large-eddy numerical simulations are presented for the transitional and turbulent flow with heat transfer in corrugated passages, representative of compact heat exchangers such as rotary air preheaters (regenerators), at Reynolds number ranging from 103 to 104. Pressure drop and heat transfer results are compared with wind-tunnel experimental data; the agreement is quite satisfactory, and superior to that obtained by more traditional methods.
Experimental Analysis of Local Pressure Losses for Microirrigation Laterals
2004
The accurate design of drip irrigation laterals needs to consider the variation of hydraulic head due to pipe elevation changes, head losses along the lines, and also, at a given operating pressure, emitter discharge variations related to manufacturing variability, clogging, and water temperature. Hydraulic head variations are consequent to both the friction losses and local losses due to the in-line or on-line emitters along the pipe, which determine the contraction and subsequent enlargement of the flow streamlines. Moreover, in-line emitters usually have a smaller diameter than the pipe, and therefore an additional friction loss must be considered. Evaluation of energy losses and consequ…
On the influence of curvature and torsion on turbulence in helically coiled pipes
2014
Turbulent flow and heat transfer in helically coiled pipes at Ret=400 was investigated by DNS using finite volume grids with up to 2.36×10^7 nodes. Two curvatures (0.1 and 0.3) and two torsions (0 and 0.3) were considered. The flow was fully developed hydrodynamically and thermally. The central discretization scheme was adopted for diffusion and advection terms, and the second order backward Euler scheme for time advancement. The grid spacing in wall units was ~3 radially, 7.5 circumferentially and 20 axially. The time step was equal to one viscous wall unit and simulations were typically protracted for 8000 time steps, the last 4000 of which were used to compute statistics. The results sho…
Liquid metal MHD experimental activities for LLCB TBM development
2013
Abstract In Indian Lead Lithium cooled Ceramic Breeder (LLCB) blanket concept, Lead–Lithium (Pb–Li) liquid metal is used to extract heat from its own bulk volume and also from the neighboring solid breeder zones. The moderate flow velocity of Pb–Li inside the module can be significantly modified due to MHD effects, which arise because of the presence of strong toroidal magnetic field. Recently, two MHD experiments have been jointly carried out at Institute of Physics, University of Latvia (IPUL) with hot Pb–Li (∼350 C) as the working fluid under a strong transverse magnetic field of up to ∼4.0 T. The uncoated test sections are made of SS316L material and consist of LLCB TBM relevant flow ge…
Numerical and experimental MHD studies of Lead-Lithium liquid metal flows in multichannel test-section at high magnetic fields
2018
Abstract Numerical simulation and experiments have been performed at high magnetic fields (1–3T) to study the MHD assisted molten Lead-Lithium (PbLi) flow in a model test-section which has typical features of multiple parallel channel flows as foreseen in various blanket module of ITER. The characteristics Hartmann number of the presented case study is up to 1557 which is relevant to typical fusion blanket conditions. Symbols B0, a, σ, μ in the definition of Hartmann number are strength of the applied magnetic field, characteristic length scale which is half the channel width parallel to the magnetic field, electrical conductivity and dynamic viscosity of PbLi respectively. Flow distributio…
Fully developed laminar flow and heat transfer in serpentine pipes
2015
Abstract A serpentine pipe is a sequence of parallel straight pipe segments connected by U-bends. Its geometry is fully characterized by pipe radius, a , bend curvature radius, c and length of the straight segments, l . The repeated curvature inversion forces the recirculation (secondary flow) pattern to switch between two specular configurations, which may enhance mixing and heat or mass transfer with respect to a constant-curvature pipe at the cost of an increase in pressure drop. In the present work, fully developed laminar flow and heat transfer in serpentine pipes were investigated by numerical simulation. The curvature δ = a / c was made to vary between 0.1 and 0.5 while the paramet…
Chemical compatibility of bulk alumina in flowing PbLi alloy under magnetic field
2021
Abstract Electrically insulating flow channel inserts (FCI) may be needed in liquid-based breeding blanket concepts to electrically decouple the metal flow from the strong magnetic field in a future fusion reactor. Although the magnetohydrodynamic simulation demonstrates a reduction of the pressure drop when a sandwich-like steel-alumina-steel FCI is employed, the tritium production efficiency in the breeding zone of a breeding blanket is limited to 550 °C due to the steel corrosion. Previous theoretical thermomechanical analyses point out the possible occurrence of induced interfacial stresses between the steel and the ceramic part. Both factors motivate the actual FCI development towards …
Influence of the porosity profile and sets of Ergun constants on the main hydrodynamic parameters in the trickle-bed reactors
2014
Abstract The Eulerian multiphase code has been applied for the comparative simulation of the experimental results obtained for varying flow rates of both fluid phases and for systems of various physicochemical properties used in the laboratory trickle-bed reactor (TBR). Therefore six different radial porosity profiles and three sets of the Ergun constants used in the relations defining the interphase momentum exchange have been implemented into the CFD code. The mean relative error of the pressure drop and of the averaged holdup as well as the standard deviation determined with respect to the experiments have been used as the criterion for the validation of the theoretical model. These valu…
Evaluation of positron-emission-tomography for visualisation of migration processes in geomaterials
2008
Abstract Positron-emission-tomography (PET) was applied for direct visualisation of solute transport in order to overcome the limitations of conventional methods for measuring advection and diffusion properties. At intervals from minutes to days the 3D-spatial distribution of the PET-tracer is determined. This spatiotemporal evolution of the tracer concentration can be used as experimental basis for clarification of the relevant transport processes, derivation of transport parameters, and model calibration. Here, 18 F and 124 I in 0.01 M carrier solution of KF and KI, respectively, have been chosen out of the limited number of available PET-tracers, primarily on account of their decay time …