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Abstract

Geometry of plate heat exchangers (PHE) is characterized by a complex net of narrow channels. It enhances turbulence and results in better heat transfer performance. Theoretically, larger number of channels (plates) should proportionally increase the PHE heat power capacity. In practice a nonuniform massflow distribution in consecutive flow channels can significantly deteriorate the overall heat exchange performance. The flow maldistribution is one of the most commonly reported exploitation problems and is present in PHE with and without phase-change flows. The presented paper investigates numerically a flow pattern in PHE with evaporation of R410A refrigerant. Various sizes of PHE are considered. The paper introduces a robust methodology to transform the complicated geometry of a real 3D PHE to its 2D representation. It results in orders of magnitude faster calculations and allows for fast evaluation of different geometrical changes of PHE and their effect on flow maldistribution.

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Authors and Affiliations

Paweł Pluszka
Arkadiusz Patryk Brenk
Ziemowit Miłosz Malecha
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Abstract

The electrostatic impulse method is an established method for producing microbeads or capsules. Such particles have found application in biomedical engineering and biotechnology. The geometric properties of the droplets – constituting precursors of microbeads and capsules – can be precisely controlled by adjusting the geometry of the nozzle system, the physical properties and the flow rate of the fluids involved, as well as the parameters of the electrostatic impulse. In this work, a method of mathematical modeling of the droplet generation process using the electrostatic impulse method in a single nozzle system is presented. The developed mathematical model is an extension of the standard Volume of Fluid (VOF) model by addition of the effect of the electric field on the fluid flow. The model was implemented into the OpenFOAM toolkit for computational fluid dynamics (CFD). The performed CFD simulation results showed good agreement with experimental data. As a result, the influence of all process parameters on the droplet generation process was studied. The most significant change in droplet generation was caused by changing the electrostatic impulse strength. The presented modeling method can be used for optimization of process design and for studying the mechanisms of droplet generation. It can be extended to describe multi nozzle systems used for one-step microcapsule production.
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Authors and Affiliations

Piotr Cendrowski
1
ORCID: ORCID
Katarzyna Kramek-Romanowska
1
ORCID: ORCID
Dorota Lewińska
2
ORCID: ORCID
Marcin Grzeczkowicz
2
ORCID: ORCID
Paulina Korycka
3
ORCID: ORCID
Jan Krzysztoforski
1
ORCID: ORCID

  1. Warsaw University of Technology, Faculty of Chemical and Process Engineering, ul. Ludwika Warynskiego 1, Warsaw, Poland
  2. Nalecz Institute of Biocybernetics and Biomedical Engineering Polish Academy of Sciences, ul. Ks. Trojdena 4, Warsaw, Poland
  3. Foundation of Research and Science Development, Rydygiera 8, 01-793 Warsaw, Poland
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Abstract

In the presented work Egorov’s approach (adding a source term to the ω-equation in the k-! model, which mimics the damping of turbulence close to a solid wall) was implemented in on the subclass of shear stress transport models. Hence, turbulence damping is available for all shear stress transport type models, including hybrid models that are based on the ω-equation. It is shown that turbulence damping improves the prediction of the axial velocity profile not only for Reynolds-averaged Navier–Stokes simulation but also for detached eddy simulation and delayed detached eddy simulation models. Furthermore, it leads to a more realistic estimation of the pressure drop and, hence, to a more correct prediction of the liquid level. In this paper, simulation results for four different turbulence models are presented and validated by comparison with experimental data. Furthermore, the influence of the magnitude of the damping factor on the pressure drop in the channel is investigated for a variety of different gas-to-liquid flow rate ratios. These investigations show that higher gas-to-liquid flow rate ratios require higher damping factors to correctly predict the pressure drop. In the end, advice is formulated on how an appropriate damping factor can be determined for a specific test case.
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Bibliography

[1] Egorov Y., Boucker M., Martin A., Pigny S., Scheuerer M., Willemsen S.: Validation of CFD codes with PTS-relevant test cases. Tech. Rep. EVOL-ECORAD07, 2004.
[2] Fabre J., Masbernat L., Suzanne C.: Stratified flow. Part I: Local structure. Multiphas. Sci. Technol. 3(1987), 285–301.
[3] Höhne T., Vallée C.: Experiments and numerical simulations of horizontal twophase flow regimes using an interfacial area density model. J. Comput. Multiphas. Flow. 2(2010), 3, 131–143.
[4] Vallée C., Höhne T.: CFD validation of stratified two-phase flows in a horizontal channel. In: Annual Report 2006 (F.-P. Weiss, U. Rindelhardt, Eds.), FZR-465, Forschungszentrum Dresden Rossendorf, 2007, 33–38.
[5] Frederix E.M.A., Mathur A., Dovizio D., Geurts B.J., Komen E.M.J.: Reynolds-averaged modeling of turbulence damping near a large-scale interface in two-phase flow. Nucl. Eng. Design 333(2018), 122–130.
[6] Höhne T., Vallée C.: Modelling of stratified two phase flows using an interfacial area density model. In: Proc. Multiphase Flow 2009, 5th Int. Conf. on Computational and Experimental Methods in Multiphase and Complex Flow, New Forest, 15-17 June, 2009, 123–133.
[7] Höhne T., Mehlhoop J.-P.: Validation of closure models for interfacial drag and turbulence in numerical simulations of horizontal stratified gas–liquid flows. Int. J. Multiphas. Flow 62(2014), 1–16.
[8] Porombka P., Höhne,T.: Drag and turbulence modelling for free surface flows within the two-fluid Euler–Euler framework. Chem. Eng. Sci. 134(2015), 348–359.
[9] Ansys Fluent User’s Guide. Release 2021 R1. Ansys, Inc., Canonsburg 2021.
[10] Chinello G., Ayati A.A., McGlinchey D., Ooms G., Henkes R.: Comparison of computational fluid dynamics simulations and experiments for stratified air-water flows in pipes. J. Fluid. Eng. 141(2019), 5, 051302-1–051302-12.
[11] Gada V.H., Tandon M.P., Elias J., Vikulov R., Lo S.: A large scale interface multi-fluid model for simulating multiphase flows. Appl. Math. Model. 44(2017), 189–204.
[12] Lo S., Tomasello A.: Recent progress in CFD modelling of multiphase flow in horizontal and near-horizontal pipes. In: Proc. 7th North American Conf. on Multiphase Technology, Banff, June 2010, BHR-2010-F1.
[13] Fan W., Li H., Anglart H.: Numerical investigation of spatial and temporal structure of annular flow with disturbance waves. Int. J. Multiphas. Flow 110(2019), 256–272.
[14] Fan W., Anglart H.: Progress in phenomenological modeling of turbulence damping around a two-phase interface. Fluids 4(2019), 3, 136.
[15] Fan W., Anglart H.: varRhoTurbVOF 2: Modified OpenFOAM volume of fluid solvers with advanced turbulence modeling capability. Comput. Phys. Commun. 256(2020), 107467.
[16] Wilcox D.C.: Turbulence Modeling for CFD Vol. 2. DCW Industries, La Canada 1998.
[17] Menter F., Kuntz M., Langtry R.: Ten years of industrial experience with the SST turbulence model. In: Turbulence, Heat and Mass Transfer 4 (K. Hanjalic, Y. Nagano, M. Tummers, Eds.). Begell House, 2003.
[18] Langtry R.B., Menter F.R.: Correlation-based transition modeling for unstructured parallelized computational fluid dynamics codes. AIAA J. 47(2009), 12, 2894–2906.
[19] Egorov Y., Menter F.: Development and application of SST-SAS turbulence model in the desider project. In: Advances in Hybrid RANS-LES Modelling (S.-H. Peng, W. Haase, Eds.), Springer, Berlin Heidelberg, 2008, 261–270.
[20] Strelets M.: Detached eddy simulation of massively separated flows. In: Proc. 39th AIAA Aerospace Sciences Meet. Exhib., Reno, Jan. 8-11, 2001.
[21] Gritskevich M., Garbaruk A., Schütze J., Menter F.: Development of DDES and IDDES formulations for the k-ω shear stress transport model. Flow Turbul. Combust. 88(2012), 3, 431–449.
[22] Müller-Steinhagen H., Heck K.: A simple friction pressure drop correlation for two-phase flow in pipes. Chem. Eng. Process. 20(1986), 6, 297–308.
[23] Launder B., Spalding D.: The numerical computation of turbulent flows. Comput. Methods Appl. Mech. Eng. 3(1974), 2, 269– 289.
[24] Menter F.R.: Two-equation eddy-viscosity turbulence models for engineering applications. AIAA J. 32(1994), 8, 1598–1605.
[25] Spalart P., Deck S., Shur M., Squires K., Strelets M., Travin A.: A new version of detached-eddy simulation, resistant to ambiguous grid densities. Theor. Comput. Fluid Dyn. 20(2006), 181–195.
[26] Frank T.: Numerical simulation of slug flow regime for an air-water two-phase flow in horizontal pipes. In: Proc. 11th Int. Topical Meeting on Nuclear Reactor Thermal-Hydraulics (NURETH-11), Avignon, Oct. 2–6, 2005.
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Authors and Affiliations

Jiri Polansky
1
Sonja Schmelter
2

  1. Czech Technical University in Prague, Jugoslávských partyzánu 1580/3, 160 00 Prague 6 – Dejvice, Czech Republic
  2. Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, D-10587 Berlin-Charlottenburg, Germany

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