Criteria for numerical modeling of low-tempe- rature non-thermal plasma

W pracy omówiono krytyczne parametry niezbędne do właściwego zdefiniowania problemu obliczeniowego z udziałem niskotemperaturowej plazmy nietermicznej w reaktorze typu DBD. Dobór tych parametrów jest zagadnieniem złożonym z uwagi na nieliniowy charakter zjawisk, przebiegających podczas wyładowań elektrycznych. Pomocne w tym zakresie są kody obliczeniowe numerycznej mechaniki płynów, które umożliwiają ilościowy opis nieliniowych relacji pomiędzy zmiennymi w czasie parametrami.Critical parameters necessary to properly define a computational problem involving a low-temperature non-thermal plasma reactor of DBD type are discussed in the paper. A choice of these parameters is a complex issue due to nonlinear nature of the phenomena which take place during the electrical discharge. The codes of computational fluid dynamics are helpful in this issue. They enable the quantitative description of non-linear relationships between the time-dependent parameters

Modelling of heat transfer in a packed bed column

The CFD modelling of heat transfer in the packed bed column in the laminar and turbulent fl ow regimes has been presented. Three numerical grids with different densities were generated for the packed bed column. The modelling was performed with the use of the Porous Media Model for treating the flow inside a porous structure. The standard k-ε model along with the logarithmic wall functions for the turbulent flow range was used. The infl uence of the mesh size on the accuracy of the fluid flow was studied. Both radial and axial direction temperature distributions have been compared with the experimental data1 and the values calculated from a 2DADPF model. A good agreement between the experimental and the predicted values of the pressure drop, temperature distributions and heat transfer coefficient was obtained

Numerical modelling of a Dielectric Barrier Discharge reactor

Przedstawiono wykorzystanie symulacji w diagnostyce warunków destrukcji lotnych związków organicznych z gazu podczas wyładowania barierowego w elemencie wyładowczym. Celem badań było opracowanie procedury modelowania umożliwiającej ujęcie zjawiska generowania plazmy i użycia aktywnych rodników do rozkładu toksycznych cząsteczek. Zastosowanie symulacji w diagnostyce warunków pracy reaktora pozwoli na optymalizację jego konstrukcji i zwiększenie skuteczności oczyszczania gazu.Application of simulation in the diagnosis of VOC destruction from gas during electric discharge in a discharge element is presented in the paper. The aim of study was to develop a modelling procedure that allows plasma generation and use of active radicals to degrade toxic molecules. The CFD procedure enables one to optimize reactor design and increase of its effectiveness. Simulations can be applied in the diagnosis of reactor's working conditions

Numerical investigation of a novel burner to combust anode exhaust gases of SOFC stacks

The aim of the present study was a numerical investigation of the efficiency of the combustion process of a novel concept burner under different operating conditions. The design of the burner was a part of the development process of a complete SOFC based system and a challenging combination of technical requirements to be fulfilled. A Computational Fluid Dynamics model of a non-premixed burner was used to simulate combustion of exhaust gases from the anode region of Solid Oxide Fuel Cell stacks. The species concentrations of the exhaust gases were compared with experimental data and a satisfactory agreement of the conversion of hydrocarbons was obtained. This validates the numerical methodology and also proves applicability of the developed approach that quantitatively characterized the interaction between the exhaust gases and burner geometry for proper combustion modelling. Thus, the proposed CFD approach can be safely used for further numerical optimisation of the burner design

CFD modelling of two-phase liquid-liquid flow in a SMX static mixer

The paper provides an overview of the application of Computational Fluid Dynamics tools for predicting transport processes in two-phase flow in a SMX static mixer. The overview is achieved by taking a brief look at factors: mesh generation, development of sub-models, post-processing including validation and quantitative verification of CFD results with experimental data. Two types of numerical approach were used in the simulations: the Reynolds averaged Navier-Stokes in the steady-state mode with the standard k-??turbulence model and Large Eddy Simulations in the unsteady mode. Both CFD techniques were applied to calculate flow velocities, pressure drop and homogenisation level in a SMX static mixer of the liquid-liquid mixture. The steady state drop size distribution was obtained by implementation procedure containing the population balance equation, where transport equations for the moments of the drop size distribution are solved and the closure problem is overcome by using the Quadrature Method of Moments

Numerical modelling of two-phase liquid - liquid flow in a SMX static mixer

Przedstawiono modelowanie przepływu dwufazowego ciecz-ciecz w mieszalniku statycznym SMX za pomocą numerycznej dynamiki płynów metodami LES i RANS. Uzyskano dobrą zgodność pomiędzy przewidywanymi i doświadczalnymi wartościami spadku ciśnienia i współczynnikami rozkładu stężeń w przestrzeni mieszalnika. Dla liczby Reynoldsa Re = 18 000 segregacja mieszanych cieczy o różnej relacji gęstości wskutek oddziaływania siły odśrodkowej charakteryzuje się podobnymi wartościami dla wyników LES i RANS.The CFD modelling of two-phase flow of liquid - liquid mixture in a SMX static mixer is presented. Two types of numerical approach were used in simulations: Large Eddy Simulations and the Reynolds averaged Navier-Stokes. A good agreement between the experimental and predicted values of pressure drop and concentration coefficient at the cross-sections of static mixer were obtained. The homogenization level reached in LES for cases 1 and 3 was similar with that obtained in RANS technique

Computational Fluid Dynamics (CFD) simulations of fluid flow through retort pipes

Praca prezentuje wykorzystanie symulacji numerycznych do diagnostyki warunków przepływu mieszaniny gazowej przez retortę. Celem badań było osiągnięcie równomiernego rozkładu prędkości gazu przy przepływie przez rury wlotowe retorty. Oceny dokonano w oparciu o współczynnik równomierności rozkładu Mk. Maksymalna wartość współczynnika dla retorty wyniosła 1,07, co stanowi wartość znacznie mniejszą od górnej dopuszczalnej wartości, po przekroczeniu której wymagana jest korekta konstrukcji aparatu.The paper presents the numerical simulation of hydrodynamics and fluid flow through inlet pipes of vertical retort. The study was aimed at determining regular velocity distributions in retort pipes. The coefficients of uniform velocity distributions, Mk, for retort pipes were estimated from numerical data. A maximum value of uniform velocity distribution coefficient was found to be equal to 1.07. This value is lower than a permissible value and is acceptable for design purposes

3D CFD fluid flow and thermal analyses of a new design of plate heat exchanger

The paper presents a Computational Fluid Dynamics (CFD) numerical study for a new design of a plate heat exchanger with two different flow patterns. The impact of geometric characteristics of the two studied geometries of exchanger plates on the intensification process of heat transfer was considered. The velocity, temperature and pressure distributions along the heat exchanger were examined. The CFD results were validated against experimental data and a good agreement was achieved. The results revealed that geometrical arrangement of the plates strongly influence the fluid flow. An increase in the Reynolds number led to lowering the friction factor value and increasing the pressure drop. The configuration II of the plate heat exchanger resulted in lower outlet hot fluid temperature in comparison with the configuration I, which means improvement of heat transfer

Modelling of processes in a microtubular Solid Oxide Fuel Cell

W pracy przedstawiono pierwszy etap opracowanej strategii modelowania, obejmujący zastosowanie dwuwymiarowego modelu numerycznego mikrorurowego stałotlenkowego ogniwa paliwowego. Zastosowane kody obliczeniowe numerycznej mechaniki płynów (CFD) umożliwiły ilościowy opis nieliniowych relacji pomiędzy parametrami: temperaturą, ciśnieniem, strumieniami substratów i produktów.Paper presents the first stage of developed modeling strategy, including the use of two-dimensional numerical model of the solid microtubular oxide fuel cell. Codes used in computational fluid dynamics (CFD) allowed a quantitative description of the non-linear relationship between parameters: temperature, pressure, substrate and product streams

Quantification of the Radiative and Convective Heat Transfer Processes and their Effect on mSOFC by CFD Modelling

The CFD modelling of heat transfer in a microtubular Solid Oxide Fuel Cell (mSOFC) stack has been presented. Stack performance predictions were based on a 16 anode-supported microtubular SOFCs sub-stack, which is a component of the overall stack containing 64 fuel cells. Both radiative and convective heat transfer were taken into account in the modelling. The heat flux value corresponded to the cell voltage of 0.7 [V]. Two different cases of the inlet air velocity of 2.0 and 8.5 [ms–1] were considered. It was found that radiation accounted for about 20–30 [%] of the total heat flux from the active tube surface, which means that the convective heat transfer predominated over the radiative one