Runge-Kutta discontinuous Galerkin method for reactive multiphase flows

International audienceA Runge-Kutta discontinuous Galerkin method is developed for the model- ing of reactive compressible multiphase flows. From the work developed in [1], where a discontinuous Galerkin formulation was obtained for inert flows based on the ideas of [2] and [3], we introduce a reactive Riemann problem [4] so as to take into account the reactions we are interested in (i.e. reactions with infinitely fast time rates). Several reactive examples are presented. The corresponding results show the high capabilities of the method, which can simulate the strong density and pressure ratios, and also has no problem whenever a phase appears or disappears

Runge-Kutta discontinuous Galerkin method for the approximation of Baer and Nunziato type multiphase models

International audienceA high-order numerical method is developed for the computation of compressible multiphase flows. The model we use is based on the Baer \& Nunziato type systems [M.R. Baer, J.W. Nunziato, A two-phase mixture theory for the deflagration-to-detonation transition (ddt) in reactive granular materials, Int. J. Multiphase Flows, 12 (12) (1986), pp. 861-889]. Among all the other available models in the literature, these systems present the advantage to be able to simulate either interface or mixture problems. Nevertheless, they still raise some issues, mainly based on their non-conservative feature. The numerical method we propose is a discontinuous Galerkin type. In this work, the interior side integrals are computed thanks to [R. Abgrall, R. Saurel, Discrete equations for physical and numerical compressible multiphase mixtures, J. Comput. Phys., 186 (361-396) (2003)]. Robustness and high order of accuracy of the method are proved on classical interface problems, but also on suitably derived analytical solutions

Runge-Kutta discontinuous Galerkin method for interface flows with a maximum preserving limiter

International audienceWe propose a high order diffuse interface method for dealing with compressible multiphase flows with interfaces. This scheme is based on the discontinuous Galerkin formulation of [E. Franquet, V. Perrier, Runge-Kutta Discontinuous Galerkin method for the approximation of Baer and Nunziato type multiphase models, Journal of Computational Physics (2012)]. As it is linear, this scheme is oscillating, so that the volume fraction can become negative or greater than 1. For stabilizing it, the maximum preserving limiter introduced in [X. Zhang, Y. Xia, C.-W. Shu, Maximum-principle-satisfying and positivity-preserving high order discontinuous Galerkin schemes for con- servation laws on triangular meshes, Journal of Scientific Computing. (2012)] is used. The scheme is applied to the computation of a Rayleigh-Taylor instability

Opportunities and economic assessment for a third-party delivering electricity, heat and cold to residential buildings

In the present context of energy transition towards a carbon neutral society, residential sector plays an important role to combat climate change since it represents about 40% of the global final energy consumption and 30% of direct CO2eq emissions in the European Union. Polygeneration systems, facilitating the integration of renewable energies, are a feasible alternative enabling efficient use of natural resources with low environmental impact. This work analyzes the economic viability, in terms of net present value (NPV), and environmental benefit (CO2eq emissions) of an energy supplier company playing the role of an aggregator for both demand and supply. As an owner of a polygeneration system, optimally designed through a MILP approach, it delivers various energy services (electricity, space heating, domestic hot water and cold) to several customers (50 dwellings). The analysis is performed, considering three different business models, in two different locations, Zaragoza (Spain) and Marseille (France), with different energy demands, energy mixes and energy regulations. The optimal configuration obtained, consisting of cogeneration module, PV, reversible heat pump, boiler and thermal energy storage has shown to be very resilient and cost-effective in the scenarios analyzed. Results indicate that the proposed scheme represents an added value for both the supplier company (aggregator), with a positive, and the final customers (owing savings greater than 30%), with significant reduction of CO2eq emissions

Influence of the turbulence model for channel flows with strong transverse temperature gradients

International audienceThe effects of a strong transverse temperature gradient on a turbulent Poiseuille flow are studied numerically using Reynolds averaged Navier–Stokes (RANS) models. Such a situation is very common for numerous industrial applications. Since a large majority of industrial computations are based on the RANS approach, the aim of the present work is to investigate the ability of different RANS models to reproduce the main physical phenomena at the origin of the asymmetry of the flow and thermal fields. Comparison are performed with available direct numerical simulations (DNS) or large eddy simulation (LES) databases. With the prospect of future application of the models in the industrial context, models based on the widely used eddy-viscosity and simple gradient diffusion (SGDH) hypotheses are compared to more elaborate second-moment closures for the Reynolds stress and turbulent heat flux. The aim is to determine the closure level necessary to reproduce the influence of strong temperature gradients on the turbulent flow, for a wide range of wall-temperature ratios. Eddy-viscosity models prove able to correctly reproduce the asymmetry of the flow and the tendency toward relaminarization close to the hot wall, which are mainly due to the strong variations of the physical properties (namely the molecular viscosity and the density). Discrepancies in the predictions of the different closure levels only appear for the highest temperature ratios. Unfortunately, reliable reference data are lacking for these configurations, which calls for future DNS or refined LES studies

IEA SHC Task 42/ECES Annex 29 – A Simple Tool for the Economic Evaluation of Thermal Energy Storages

Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)Within the framework of IEA SHC Task 42 / ECES Annex 29, a simple tool for the economic evaluation of thermal energy storages has been developed and tested on various existing storages. On that account, the storage capacity costs (costs per installed storage capacity) of thermal energy storages have been evaluated via a Top-down and a Bottom-up approach. The Top-down approach follows the assumption that the costs of energy supplied by the storage should not exceed the costs of energy from the market. The maximum acceptable storage capacity costs depend on the interest rate assigned to the capital costs, the intended payback period of the user class (e.g. industry or building), the reference energy costs, and the annual number of storage cycles. The Bottom-up approach focuses on the realised storage capacity costs of existing storages. The economic evaluation via Top-down and Bottom-up approach is a valuable tool to make a rough estimate of the economic viability of an energy storage for a specific application. An important finding is that the annual number of storage cycles has the largest influence on the cost effectiveness. At present and with respect to the investigated storages, seasonal heat storage is only economical via large sensible hot water storages. Contrary, if the annual number of storage cycles is sufficiently high, all thermal energy storage technologies can become competitive.This study is part of IEA SHC Task 42 / ECES Annex 29 „Compact Thermal Energy Storage - Material Development and System Integration“ (http://task42.iea-shc.org). The work of ZAE Bayern is part of the project PC-Cools_V and supported by the German Federal Ministry for Economic Affairs and Energy under the project code 03ESP138A. University of Zaragoza thanks the Spanish Government for the funding of their work under the projects ENE2008-06687-C02-02, ENE2011-28269-C03-01 and ENE2014-57262-R. University of Lleida would like to thank the Catalan Government for the quality accreditation given to their research group (2014 SGR 123). The research leading to these results has received funding from the European Union's Seventh Framework Program (FP7/2007-2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and European Union’s Horizon 2020 research and innovationprogramme under grant agreement No 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). The University of the Basque Country acknowledges the financial support of the Spanish’s Ministry of Economy and Competitiveness through the MicroTES (ENE2012- 38633) research project. The responsibility for the content of this publication is with the author

Inverse technique in thermal heat storage

INVInternational audienc

Storage of thermal energy

International audienc

Storage of thermal energy

INVInternational audienc