FG Thermodynamik und Thermische Verfahrenstechnik

48 Items

Recent Submissions
Investigating the real life energy consumption of refrigeration appliances in Germany: Are present policies sufficient?

Hueppe, Christian ; Geppert, Jasmin ; Moenninghoff-Juessen, Julia ; Wolff, Lena ; Stamminger, Rainer ; Paul, Andreas ; Elsner, Andreas ; Vrabec, Jadran ; Wagner, Hendrik ; Hoelscher, Heike ; Becker, Wolfgang ; Gries, Ulrich ; Freiberger, Alfred (2021-05-18)

Domestic refrigeration appliances are standard household commodities. Although policies, such as the energy labelling, prompted technical improvements and decreased appliance energy consumption throughout recent decades, important parameters were disregarded. These refer to the efficiency loss over time and the consumer behaviour. The objective of this contribution was to develop a dynamic ener...

Density and partial molar volumes of the liquid mixture water + methanol + ethanol + 2-propanol at 298.15 K and 0.1 MPa

Guevara-Carrion, Gabriela ; Fingerhut, Robin ; Vrabec, Jadran (2021-06-01)

The density of the quaternary mixture water + methanol + ethanol + propan-2-ol and its four ternary and six binary subsystems is measured over a wide composition range at ambient temperature and pressure, that is, 298.15 K and 0.1 MPa. The resulting molar volume data are correlated with a response surface model, consisting of linear, quadratic, bilinear, and trilinear interaction terms. The den...

Diffusion in multicomponent aqueous alcoholic mixtures

Guevara-Carrion, Gabriela ; Fingerhut, Robin ; Vrabec, Jadran (2021-06-10)

The Fick diffusion coefficient matrix of the highly associating quaternary mixture water + methanol + ethanol + 2-propanol as well as its ternary and binary subsystems is analyzed with molecular dynamics simulation techniques. Three of the ternary subsystems are studied in this sense for the first time. The predictive capability of the employed force fields, which were sampled with the Green–Ku...

Experimental study of two cascaded organic Rankine cycles with varying working fluids

Abbas, Wameedh Khider Abbas ; Linnemann, Matthias ; Baumhögger, Elmar ; Vrabec, Jadran (2021-01-09)

Organic Rankine cycles convert low-temperature heat from different sources, like solar, geothermal or biomass, into electricity and may thus help to meet the energy demand in an environmentally friendly way. While single ORC systems have been studied extensively, there are only very few experimental works on systems consisting of two cascaded organic Rankine cycles (two-ORC). In this work, an e...

AutoPas in ls1 mardyn: Massively parallel particle simulations with node-level auto-tuning

Seckler, Steffen ; Gratl, Fabio ; Heinen, Matthias ; Vrabec, Jadran ; Bungartz, Hans-Joachim ; Neumann, Philipp (2021-01-07)

Due to computational cost, simulation software is confronted with the need to always use optimal building blocks — data structures, solver algorithms, parallelization schemes, and so forth — in terms of efficiency, while it typically needs to support a variety of hardware architectures. AutoPas implements the computationally most expensive molecular dynamics (MD) steps (e.g., force calculation)...

Comparison of macro- and microscopic solutions of the Riemann problem II. Two-phase shock tube

Hitz, Timon ; Jöns, Steven ; Heinen, Matthias ; Vrabec, Jadran ; Munz, Claus-Dieter (2020-11-27)

The Riemann problem is one of the basic building blocks for numerical methods in computational fluid mechanics. Nonetheless, there are still open questions and gaps in theory and modeling for situations with complex thermodynamic behavior. In this series, we compare numerical solutions of the macroscopic flow equations with molecular dynamics simulation data. To enable molecular dynamics for su...

ms2: A molecular simulation tool for thermodynamic properties, release 4.0

Fingerhut, Robin ; Guevara-Carrion, Gabriela ; Nitzke, Isabel ; Saric, Denis ; Marx, Joshua ; Langenbach, Kai ; Prokopev, Sergei ; Celný, David ; Bernreuther, Martin ; Stephan, Simon ; Kohns, Maximilian ; Hasse, Hans ; Vrabec, Jadran (2021-01-30)

A new version release (4.0) of the molecular simulation tool ms2 (Deublein et al. 2011; Glass et al. 2014; Rutkai et al. 2017) is presented. Version 4.0 of ms2 features two additional potential functions to address the repulsive and dispersive interactions in a more versatile way, i.e. the Mie potential and the Tang–Toennies potential. This version further introduces Kirkwood–Buff integrals bas...

Diffusion of the carbon dioxide–ethanol mixture in the extended critical region

Chatwell, René Spencer ; Guevara-Carrion, Gabriela ; Gaponenko, Yuri ; Shevtsova, Valentina ; Vrabec, Jadran (2021-01-18)

The effect of traces of ethanol in supercritical carbon dioxide on the mixture's thermodynamic properties is studied by molecular simulations and Taylor dispersion measurements. This mixture is investigated along the isobar p = 10 MPa in the temperature range between T = 304 and 343 K. Along this path, the mixture undergoes two transitions: First, the Widom line is crossed, marking the transiti...

Speed of sound measurement for industrially important fluids with the pulse-echo technique

Javed, Muhammad Ali (2020)

Because of its thermal and caloric nature, thermodynamic speed of sound data covering wide temperature and pressure ranges are crucial for the development of high quality Helmholtz energy equations of state. These fundamental equations of state are required to provide thermodynamic properties for the design and optimization of a wide range of technical processes. Moreover, speed of sound data i...

Evaporation driven by conductive heat transport

Homes, Simon ; Heinen, Matthias ; Vrabec, Jadran ; Fischer, Johann (2020-10-24)

Molecular dynamics simulations are conducted to investigate the evaporation of the truncated (2.5σ) and shifted Lennard–Jones fluid into vacuum. Evaporation is maintained under stationary conditions, while the bulk liquid temperature and the thermal driving force gradient are varied over wide ranges. It is found that the particle flux and the energy flux solely depend on the interface temperatu...

Improving the performance of household refrigerating appliances through the integration of phase change materials in the context of the new global refrigerator standard IEC 62552:2015

Sonnenrein, Gerrit ; Baumhögger, Elmar ; Elsner, Andreas ; Morbach, A. ; Neukötter, M. ; Paul, Andreas ; Vrabec, Jadran (2020-08-01)

The influence of latent heat storage elements on the cooling performance and the temperature rise time of household refrigerating appliances is studied experimentally in the context of the “new global refrigerator standard” IEC 62552:2015. In addition to the daily energy consumption, this international standardization introduced performance tests for cooling capacity and temperature rise time. ...

Determining the heat flow through the cabinet walls of household refrigerating appliances

Paul, Andreas ; Baumhögger, Elmar ; Elsner, Andreas ; Moczarski, Lukas ; Reineke, Michael ; Sonnenrein, Gerrit ; Hueppe, Christian ; Stamminger, Rainer ; Hoelscher, Heike ; Wagner, Hendrik ; Gries, Ulrich ; Freiberger, Alfred ; Becker, Wolfgang ; Vrabec, Jadran (2020-10-07)

The increase of the thermal conductivity of PUR foam in the insulation of the cabinet is an important cause for aging processes of household refrigerating appliances. To determine the influence of the PUR foam aging on energy consumption, the development of a new measurement method is necessary because current methods influence the aging behavior of household refrigerators and are therefore not...

Molecular simulation study of the curling behavior of the finite free-standing kaolinte layer

Ható, Zoltán ; Vrabec, Jadran ; Kristóf, Tamás (2020-10-16)

Since kaolinite nanolayers potentially have many important applications, it is crucial to determine the factors that govern their curling behavior. The curling of a single-layer, free-standing kaolinite nanoparticle consisting of nearly 1 million atoms is studied with classical molecular dynamics simulation. Two up-to-date force fields are employed to describe the atomic interactions in the cla...

Structure and dynamics of the Lennard-Jones fcc-solid focusing on melting precursors

Mausbach, Peter ; Fingerhut, Robin ; Vrabec, Jadran (2020-09-09)

The Lennard-Jones potential is taken as a basis to study the structure and dynamics of the face centered cubic (fcc) solid along an isochore from low temperatures up to the solid/fluid transition. The Z method is applied to estimate the melting point. Molecular dynamics simulations are used to calculate the pair distribution function, numbers of nearest neighbors, and the translational order pa...

Density and Thermodynamic Speed of Sound of Liquid Vinyl Chloride

Javed, Muhammad Ali ; Rüther, Moritz ; Baumhögger, Elmar ; Vrabec, Jadran (2020-04-23)

Vinyl chloride is one of the world’s most important industrially synthesized substances, but due to its physicochemical nature, comparably little is known about its thermodynamic behavior. Accurate density and thermodynamic speed of sound data of vinyl chloride in the liquid state are measured along nine isotherms, covering the temperature range from 283 to 362 K up to a pressure of 91 MPa. Dat...

Fick Diffusion Coefficient Matrix of a Quaternary Liquid Mixture by Molecular Dynamics

Guevara-Carrion, Gabriela ; Fingerhut, Robin ; Vrabec, Jadran (2020-03-23)

For the first time, the Fick diffusion coefficient matrix of a quaternary liquid mixture is sampled consistently by means of molecular dynamics simulation. The required phenomenological diffusion coefficient and thermodynamic factor matrices of the mixture water + methanol + ethanol + 2-propanol are determined following the Green–Kubo formalism and Kirkwood–Buff theory. Further, a system size c...

Molecular Modeling and Simulation: Force Field Development, Evaporation Processes and Thermophysical Properties of Mixtures

Janzen, Tatjana ; Fingerhut, Robin ; Heinen, Matthias ; Köster, Andreas ; Muñoz-Muñoz, Y. Mauricio ; Vrabec, Jadran (2019-06-08)

To gain physical insight into the behavior of fluids on a microscopic level as well as to broaden the data base for thermophysical properties especially for mixtures, molecular modeling and simulation is utilized in this work. Various methods and applications are discussed, including a procedure for the development of new force field models. The evaporation of liquid nitrogen into a supercritic...

PetaFLOP Molecular Dynamics for Engineering Applications

Neumann, Philipp ; Tchipev, Nikola ; Seckler, Steffen ; Heinen, Matthias ; Vrabec, Jadran ; Bungartz, Hans-Joachim (2019-06-08)

Molecular dynamics (MD) simulations enable the investigation of multicomponent and multiphase processes relevant to engineering applications, such as droplet coalescence or bubble formation. These scenarios require the simulation of ensembles containing a large number of molecules. We present recent advances within the MD framework ls1 mardyn which is being developed with particular regard to t...

A Benchmark Open-Source Implementation of COSMO-SAC

Bell, Ian H. ; Mickoleit, Erik ; Hsieh, Chieh-Ming ; Lin, Shiang-Tai ; Vrabec, Jadran ; Breitkopf, Cornelia ; Jäger, Andreas (2020-02-14)

The COSMO-SAC modeling approach has found wide application in science as well as in a range of industries due to its good predictive capabilities. While other models for liquid phases, as for example UNIFAC, are in general more accurate than COSMO-SAC, these models typically contain many adjustable parameters and can be limited in their applicability. In contrast, the COSMO-SAC model only conta...

Henry’s Law Constant of Nitrogen, Oxygen, and Argon in Ternary Aqueous Alcoholic Solvent Mixtures

Malviya, Abhigyan ; Vrabec, Jadran (2019-08-12)

Henry’s law constant data for nitrogen, oxygen, and argon in the ternary liquid mixture water + methanol + ethanol as well as its pure and binary solvent subsystems are reported. The composition and temperature dependence of the Henry’s law constant of the air components in these solutions is investigated by Monte Carlo simulation. The underlying molecular force field models are based on the mo...