169 research outputs found
Economic Topology Optimization of District Heating Networks using a Pipe Penalization Approach
In the presented study, a pipe penalization approach for the economic
topology optimization of District Heating Networks is proposed, drawing
inspiration from density-based topology optimization. For District Heating
Networks, the upfront investment is a crucial factor for the rollout of this
technology. Today, the pipe routing is usually designed relying on a
linearization of the underlying heat transport problem. This study proposes to
solve the optimal pipe routing problem as a non-linear topology optimization
problem, drawing inspiration from density-based topology optimization. The
optimization problem is formulated around a non-linear heat transport model and
minimizes a detailed net present value representation of the heating network
cost. By relaxing the combinatorial problem of pipe placement, this approach
remains scalable for large-scale applications. A discrete network topology and
near-discrete pipe design is achieved by using an intermediate pipe
penalization strategy. For a realistic test case, the proposed algorithm
achieves a discrete network topology and near-discrete pipe design that
outperforms simple post-processing steps.Comment: Changed article template and minor reformulations in abstract,
introduction and conclusio
Hilbert expansion based fluid models for kinetic equations describing neutral particles in the plasma edge of a fusion device
Neutral particles in the plasma edge of fusion devices based on magnetic
confinement are described by a transient kinetic equation incorporating
ionization, recombination, and charge-exchange collisions. In charge-exchange
dominated regimes, the neutral particle velocity distribution approaches the
drifting Maxwellian defined by the mean velocity and temperature of the plasma.
This enables model order reduction from the kinetic equation to approximate
fluid models. We derive transient fluid models consistent with the kinetic
equation by exploring a splitting based approach. We split the kinetic equation
in sources and sinks on the one hand, and transport combined with
charge-exchange on the other hand. Combining transport with charge-exchange
collisions allows for deriving Hilbert expansion based fluid models. The
retrieved fluid models depend on the assumed importance (scaling) of the
different terms in the split equation describing transport and charge-exchange.
We explore two scalings: the hydrodynamic scaling and the diffusive scaling.
The performance of the fluid models with respect to a discrete velocity model
and a Monte Carlo reference solver is assessed in numerical experiments. The
code used to perform the numerical experiments is openly available.Comment: 22 pages, 5 figures. This article may be downloaded for personal use
only. Any other use requires prior permission of the author and AIP
Publishing. This article appeared in Physics of Plasmas (Vol.30, Issue 6) and
may be found at https://doi.org/10.1063/5.014615
Developed and quasi-developed macro-scale flow in micro- and mini-channels with arrays of offset strip fins
We investigate to what degree the steady laminar flow in typical micro- and
mini-channels with offset strip fin arrays can be described as developed on a
macro-scale level, in the presence of channel entrance and side-wall effects.
Hereto, the extent of the developed and quasi-developed flow regions in such
channels is determined through large-scale numerical flow simulations. It is
observed that the onset point of developed flow increases linearly with the
Reynolds number and channel width, but remains small relative to the total
channel length. Further, we find that the local macro-scale pressure gradient
and closure force for the (double) volume-averaged Navier-Stokes equations are
adequately modeled by a developed friction factor correlation, as typical
discrepancies are below 15% in both the developed and developing flow region.
We show that these findings can be attributed to the eigenvalues and mode
amplitudes which characterize the quasi-developed flow in the entrance region
of the channel. Finally, we discuss the influence of the channel side walls on
the flow periodicity, the mass flow rate, as well as the macro-scale velocity
profile, which we capture by a displacement factor and slip length coefficient.
Our findings are supported by extensive numerical data for fin height-to-length
ratios up to 1, fin pitch-to-length ratios up to 0.5, and channel aspect ratios
between 1/5 and 1/17, covering Reynolds numbers from 28 to 1224.Comment: 48 pages, 25 figure
Numerical analysis of a cross-flow fan with two outlets
Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.Cross Flow Fans (CFFs) are used in air
conditioning and ventilation technology because of their
compact design and low noise. In addition, CFFs can
provide a uniform velocity profile along the width of the
fan. This offers an enormous advantage in applications
with large width to diameter ratios as needed. However,
as the flow pattern inside a CFF is very complex,
classical fan design is not applicable. At present, the
design of CFFs is most often based on experimental
investigation and empirical experience. In order to
investigate the behaviour of these type of fans and its
relation to the complex flow structure inside casing and
rotor, CFD-simulations are carried out. In this study,
transient solutions for a two dimensional viscous and
incompressible model of the fan are used to assess the
cross flow fan with two parallel outlets. The impact of
the outlet configuration on the flow patterns is thereby
numerically investigated. It is shown that both the
diffuser and the position of the vortex wall play a crucial
role to achieve stable and balanced volumetric flows
through the two outlets.cs201
Towards automated magnetic divertor design for optimal heat exhaust
International audienceAvoiding excessive structure heat loads in future fusion tokamaks is regarded as one of the greatest design challenges. In this paper, we aim at developing a tool to study how the severe divertor heat loads can be mitigated by reconfiguring the magnetic confinement. For this purpose, a free boundary equilibrium code is integrated with a plasma edge transport code to work in an automated fashion. Next, a practical and efficient adjoint based sensitivity calculation is proposed to evaluate the sensitivities of the integrated code. The sensitivity calculation is finally applied to a realistic test case and compared with finite difference sensitivity calculations
EUROfusion Integrated Modelling (EU-IM) capabilities and selected physics applications
International audienceRecent developments and achievements of the EUROfusion Code Development for Integrated Modelling project (WPCD), which aim is to provide a validated integrated modelling suite for the simulation and prediction of complete plasma discharges in any tokamak, are presented. WPCD develops generic complex integrated simulations, workflows, for physics applications, using the standardized European Integrated Modelling (EU-IM) framework. Selected physics applications of EU-IM workflows are illustrated in this paper
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