# Jadran VrabecTechnische Universität Berlin | TUB · Process Sciences

Jadran Vrabec

Prof. Dr.-Ing. habil.

Messing around

## About

335

Publications

172,174

Reads

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9,271

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Introduction

Jadran Vrabec currently works at the Faculty of Process Sciences, Technische Universität Berlin. Jadran does research in Thermodynamics, Molecular Modelling and Simulation as well as Computational Physics.

Additional affiliations

January 2009 - August 2018

October 1999 - December 2008

January 1989 - July 1996

## Publications

Publications (335)

The quantum mechanics-aided COSMO-SAC activity coefficient model is applied and systematically examined for predicting the thermodynamic compatibility of drugs and polymers. Drug-polymer compatibility is a key aspect in the rational selection of optimal polymeric carriers for pharmaceutical amorphous solid dispersions (ASD) that enhance drug bioava...

Thermodynamic potentials play a substantial role in numerous scientific disciplines and serve as basic constructs for describing the behavior of matter. Despite their significance, comprehensive investigations of their topological characteristics and their connections to molecular interactions have eluded exploration due to experimental inaccessibi...

A fundamental equation of state in terms of the Helmholtz energy is presented for mixtures of nitrogen, oxygen, and argon at any composition. It is expressed in terms of the residual Helmholtz energy and can be used to calculate all thermodynamic equilibrium properties including vapor–liquid equilibria. The parameters of the equations for the pure-...

A model for the dynamic pressure loss in standard oleo-pneumatic shock absorbers without gas-oil separator for avionics applications is introduced. The dynamics of such a device under load variations is primarily determined by the throttle between the oil chamber and the gas chamber. During operation, gas is absorbed by the oil upon compression and...

Entropy scaling is applied to the shear viscosity, self-diffusion coefficient, and thermal conductivity of simple monatomic fluids. An extensive molecular dynamics simulation series is performed to obtain these transport properties and the residual entropy of three potential model classes with variable repulsive exponents: n, 6 Mie (n = 9, 12, 15,...

Heat and mass transfer across the interface between liquid and vapor is studied by means of molecular dynamics simulation. Two scenarios are considered to access the interface resistivities, specifying either the evaporation rate or the temperature gradient. Spatially resolved profiles of density, temperature, chemical potential, pressure tensor el...

Digitalization is a priority for innovation in the engineering sciences. The digital transformation requires making the knowledge claims from scientific research data machine-actionable, so that they can be integrated and analysed with minimal human intervention. Up until now, the depth of digitalization is often too shallow, with annotations that...

Vapor–liquid equilibria of the binary mixtures argon–ammonia, methane–ammonia, hydrogen–ammonia, nitrogen–ammonia, and oxygen–ammonia are investigated by utilizing Monte Carlo and molecular dynamics simulations up to pressures of 100 MPa and beyond. At three different temperatures ranging from 233.15 to 377.59 K, the vapor pressure, densities of th...

Mutual diffusion of six hydrocarbons (methane, ethane, isobutane, benzene, toluene or naphthalene) diluted in supercritical carbon dioxide (CO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-6...

This study investigates phase equilibria and transport properties of five symmetric binary Lennard-Jones mixtures using molecular simulation and equation of state models. The mixtures are selected for their representation of different types of phase behavior and the research contributes to the development of simulation techniques, mixture theories...

Generalized expressions for thermodynamic properties in terms of ensemble averages are discussed for adiabatic and isothermal ensembles. They are implemented in the simulation code ms2 and validated by Monte Carlo simulations for the Lennard-Jones fluid. A comparison of the eight statistical ensembles regarding size scaling behavior, convergence, a...

A multitude of industries, including energy and process engineering, as well as academia are researching and utilizing new fluid substances to further the aim of sustainability. Knowledge of the thermodynamic properties of these substances is a prerequisite, if they are to be utilized to their fullest potential. To date, the way to acquire reliable...

The molecular interactions of numerous real fluids, like argon, nitrogen, or carbon dioxide, are adequately described by the two-center Lennard-Jones plus quadrupole potential. Applying this model class in molecular dynamics simulations, evaporation is investigated systematically. The influence of the molecular anisotropy and quadrupole as well as...

Digitalization is a priority for innovation in the engineering sciences. The digital transformation requires making the knowledge claims from scientific research data machine-actionable, so that they can be integrated and analysed with minimal human intervention. Up until now, the depth of digitalization is often too shallow, with annotations that...

The technical importance of paraffins as phase change materials (PCM) in heat storage systems increases. Knowledge on the thermal conductivity of paraffins is necessary for the design and optimization of heat storage systems. However, for most paraffins solely the thermal conductivity of the liquid state has been sufficiently investigated. For the...

An empirical multi-parameter equation of state in terms of the reduced Helmholtz energy is presented for the Mie ( λ r -6) fluid with a repulsive exponent λ r from 11 to 13. The equation is fitted to an extensive dataset from molecular dynamics simulation as well as the second and third thermal virial coefficients. It is comprehensively compared wi...

Vapor-liquid equilibria and fluid interface properties of binary mixtures containing either methane or cyclohexane representing fuel and nitrogen or oxygen are reported. The mixtures are studied at different temperatures and pressures, which are chosen such that the temperature of the fuel component is subcritical, while that of the gaseous compone...

This document reports on the outcomes from the second stage of our case study on epistemic metadata in molecular modelling. It builds on the outcomes from the first stage as summarized in the first-stage report, doi:10.5281/zenodo.7516532.

This chapter covers scaling issues related to our recent work in the field of molecular dynamics simulations with a focus on computational details. The first section deals with finite size effects in the context of multicomponent diffusion. Different methods to correct the influence of the finite simulation domain are compared. In the second sectio...

The bulk viscosity, a transport coefficient in the Navier-Stokes equation, is often neglected in the continuum mechanics of Newtonian fluids. Recently, however, the role of the bulk viscosity is highlighted in the area of surface and interface-related phenomena, in systematic model up-scaling and as an important quantity for the interpretation of a...

Supercritical carbon dioxide (scCO2) mixtures are essential for many industrial applications. However, the knowledge of their thermophysical properties in the extended critical region is insufficient. Here, supercritical liquid- and gas-like regions dominated by distinct dynamics and thermodynamics exist and are demarcated by the so-called Widom li...

Two boundary lines are frequently discussed in the literature, separating state regions dominated by repulsion or attraction. The Fisher-Widom line indicates where the longest-range decay of the total pair correlation function crosses from monotonic to exponentially damped oscillatory. In the context of thermodynamic metric geometry, such a transit...

Due to availability of powerful computers and efficient algorithms, physical processes occurring at the micrometer scale can nowadays be studied with atomistic simulations. In the framework of the collaborative research center SFB-TRR75 “Droplet dynamics under extreme ambient conditions”, investigations of the mass transport across vapour-liquid in...

A fundamental equation of state is presented for 1-hexene. It is explicit in the reduced Helmholtz energy and depends on the independent variables temperature and density. It is valid in the fluid region at temperatures from the triple–point temperature Ttr = 133.39 K to Tmax = 535 K with a maximum pressure of pmax = 245 MPa. All thermodynamic prop...

The thermodiffusion behavior of binary Lennard‐Jones mixtures in the liquid state is investigated by combining the individual strengths of non‐equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) simulations. On the one hand, boundary‐driven NEMD simulations are useful to quickly predict Soret coefficients because they are...

It is shown that the residual entropy (entropy minus that of the ideal gas at the same temperature and density) is mostly synonymous with the independent variable of density scaling, identifying a direct link between these two approaches. The residual entropy and the effective hardness of interaction (itself a derivative at constant residual entrop...

The thermodiffusion behavior of binary Lennard-Jones mixtures in the liquid state was investigated by combining the individual strengths of non-equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) simulations. On the one hand, boundary-driven NEMD simulations are useful to quickly predict Soret coefficients because they ar...

An experimental investigation of the organic Rankine cycle (ORC) is carried out using butane, pentane, cyclopentane or hexamethyldisiloxane as a working fluid. Thermal and exergy efficiencies are used to assess system performance over a wide range of heat source temperature, turbine inlet pressure and superheating degree. The results indicate that...

It is shown that the residual entropy (entropy minus that of the ideal gas at the same temperature and density) is mostly synonymous with the independent variable of density scaling, identifying a direct link between these two approaches. The two-body residual entropy is demonstrated to not be a suitable surrogate for the total residual entropy in...

The potential function suggested by Tang and Toennies is parametrised to represent the thermodynamic properties of argon. The fit of its parameters is carried out on the basis of different data obtained by molecular dynamics simulation and integration of Mayer's f function. Apart from usual optimisation procedures, an efficient strategy based on re...

Thermodiffusion is a coupled heat and mass transport process, in which a temperature gradient initiates the separation of components in a mixture. It occurs in many natural and technical processes, but experimental measurements are indirect and expensive. Therefore, molecular simulations are valuable to quickly predict transport properties such as...

While preparing a recently published article by some of the authors of this correction, (1) we noticed that the parameters of the water model presented in the original paper by Huang et al. (2) were misprinted. Those misprints were carried over to a paper by Köster et al. (3) The misprinted parameters are the two lengths in the water model: the OH...

Coalescence of argon droplets with a radius of 25, 50, and 100 nm is studied with computational methods. Molecular dynamics (MD) simulations are carried out to generate reference data. Moreover, a phase-field model resting on a Helmholtz energy equation of state is devised and evaluated by computational fluid dynamics (CFD) simulations. Exactly the...

The speed of sound is a thermodynamic equilibrium property which relates pressure to density variations at constant entropy. Because of its thermal and caloric nature, thermodynamic speed of sound data are crucial for the parametrization of highly accurate Helmholtz energy equations of state, which are in great demand. In the present work, the ther...

Vapor-liquid, liquid-liquid and vapor-liquid-liquid equilibria of the binary system nitrogen + ethane are investigated systematically for temperatures between 105 and 260 K and pressures between 15 and 150 bar. Force field models are used that have been parameterized beforehand solely to vapor-liquid equilibrium data and are augmented by a single b...

The performance of thermodynamic models is assessed with respect to Joule-Thomson inversion on the basis of 29 fluids with varying molecular structure. Three thermodynamic model types are considered: classical force fields, the molecular-based PC-SAFT equation of state (EOS) and empirical multi-parameter EOS. The force fields consist of Lennard-Jon...

The homogeneous density of the liquid phase is experimentally investigated for methyl diethanolamine. Data are obtained along five isotherms in a temperature range between 300 K and 360 K for pressures up to 95 MPa. Two different apparatuses are used to measure the speed of sound for the temperatures between 322 K and 450 K with a maximum pressure...

We are outlining our most recent findings, covering: 1) A comparison of a micro- and macroscopic solution of a two-phase Riemann problem obtained from molecular dynamics simulations and finite volume schemes; 2) A novel equation of state for the bulk viscosity of liquid noble gases based on a multi-mode relaxation ansatz; 3) A detailed analysis of...

A cascaded dual-loop organic Rankine cycle (CD-ORC) consisting of a high-temperature ORC (HT-ORC) and a low-temperature ORC (LT-ORC) with a shared heat exchanger is studied. Thermal efficiency is investigated as a key indicator for system performance over a wide range of heat source temperature ranging from 170 °C to 330 °C. The relation between th...

The parameters required to calculate the energy efficiency of household refrigerating appliances (i.e. refrigerators, freezers and their combinations) are determined by standard measurements. According to regulations, these measurements are carried out when the appliances are new. It is known from previous studies that various technical aging mecha...

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...

Long range corrections for molecular simulations of inhomogeneous fluids with a spherical interface are presented. Correction terms for potential energy, force and virial are derived for the monatomic Lennard–Jones fluid. The method is generalised to the Mie potential and arbitrary molecular structures, employing a numerically efficient centre of m...

A measurement procedure using a modified two-chamber pulse-echo experimental setup is presented, enabling acoustic absorption and bulk viscosity (volume viscosity) measurements in liquids up to high temperature and pressure. Acoustic absorption measurements are particularly challenging, since other dissipative effects, such as diffraction at the ac...

Presenting a new method to investigate metastable system condition using molecular dynamics simulation with custom criteria for cluster detection.

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 for...

The MolMod database is presented, which is openly accessible at http://molmod.boltzmann-zuse.de andcontains intermolecular force fields for over 150 pure fluids at present. It was developed and is maintainedby the Boltzmann-Zuse Society for Computational Molecular Engineering (BZS). The set of molecularmodels in the MolMod database provides a coher...

Literature data on the thermophysical properties of the Lennard-Jones fluid, which were sampled with molecular dynamics and Monte Carlo simulations, were reviewed and assessed. The literature data were complemented by simulation data from the present work that were taken in regions in which previously only sparse data were available. Data on homoge...

Digitalization is about data and how they are used. This has always been a key topic in applied thermodynamics. In the present work, the influence of the current wave of digitalization on thermodynamics is analyzed. Thermodynamic modeling and simulation is changing as large amounts of data of different nature and quality become easily available. Th...

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 organ...

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...

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,...

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 organ...

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 molecula...

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...

Molecular dynamics simulations are conducted to investigate the evaporation of the truncated ( 2.5 σ ) 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 en...

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 o...

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 ne...

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 (IEC 62552:2015, 2015). In addition to the daily energy consumption, this international standardization introdu...