Blar i NTNU Open på forfatter "Wilhelmsen, Øivind"
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The influence of interfacial transfer and film coupling in the modeling of distillation columns to separate nitrogen and oxygen mixtures
Kingston, Diego; Wilhelmsen, Øivind; Kjelstrup, Signe (Peer reviewed; Journal article, 2020)Coupling between heat and mass transfer occurs across interfaces and in vapor and liquid films. In this work, we present the first rigorous investigation of the role of these physical phenomena in the mathematical modeling ... -
The influence of thermal diffusion on water migration through a porous insulation material
Jervell, Vegard Gjeldvik; Gjennestad, Magnus Aashammer; Trinh, Thuat T.; Wilhelmsen, Øivind (Journal article; Peer reviewed, 2024)Excess water on pipes and equipment under porous insulation materials can lead to undesired corrosion. This work aims to clarify to what extent thermal diffusion affects the migration of water inside insulation materials ... -
Limiting current density as a selectivity factor in electrodialysis of multi-ionic mixtures
Zimmermann, Pauline; Tekinalp, Önder; Solberg, Simon Birger Byremo; Wilhelmsen, Øivind; Deng, Liyuan; Burheim, Odne Stokke (Peer reviewed; Journal article, 2023)Electrodialysis is a promising technology to remove low concentrations of target ions from multi-ionic mixtures. While the synthesis of selective membranes is a prominent topic in research, few studies have been presented ... -
Local equilibrium in liquid phase shock waves
Maltby, Tage Winther; Hafskjold, Bjørn; Bedeaux, Dick; Kjelstrup, Signe; Wilhelmsen, Øivind (Peer reviewed; Journal article, 2023) -
Mie–FH: A quantum corrected pair potential in the LAMMPS simulation package for hydrogen mixtures
Trinh, Thuat T.; Hammer, Morten; Sharma, V.; Wilhelmsen, Øivind (Journal article; Peer reviewed, 2024)Several knowledge gaps on the properties and behavior of hydrogen must be closed to realize its widespread use as a clean fuel and reduction agent. A challenge in this regard is that hydrogen and its mixtures are influenced ... -
Minimum entropy generation in a heat exchanger in the cryogenic part of the hydrogen liquefaction process: On the validity of equipartition and disappearance of the highway
Hånde, Ragnhild; Wilhelmsen, Øivind (Journal article; Peer reviewed, 2019)Liquefaction of hydrogen is a promising technology for transporting large quantities of hydrogen across long distances. A key challenge is the high power consumption. In this work, we discuss refrigeration strategies that ... -
Minimum entropy production in a distillation column for air separation described by a continuous non-equilibrium model
Kingston, Diego; Wilhelmsen, Øivind; Kjelstrup, Signe (Journal article; Peer reviewed, 2020)In this work, we apply the rate-based model of Taylor and Krishna to describe the separation of air in a low-pressure, packed distillation column. By use of numerical optimization, we identify the temperature profile for ... -
Modelling of two-phase equilibrium, stability and steady-state flow in porous media
Gjennestad, Magnus Aashammer (Doctoral theses at NTNU;2020:364, Doctoral thesis, 2020)This thesis concerns fundamental aspects of coexistence and flow of two fluid phases within porous media. Specifically, the focus is on thermodynamic stability and equilibrium on the scale of a single pore and on macroscopic ... -
Nonequilibrium thermodynamics of surfaces captures the energy conversions in a shock wave
Hafskjold, Bjørn; Bedeaux, Dick; Kjelstrup, Signe; Wilhelmsen, Øivind (Peer reviewed; Journal article, 2020)A theory for the entropy production in a shock wave was developed using Gibbs’ excess properties in the framework of non-equilibrium thermodynamics (NET) of surfaces. The theory was used to analyze numerical results from ... -
One-dimensional mathematical modeling of two-phase ejectors: Extension to mixtures and mapping of the local exergy destruction
Wilhelmsen, Øivind; Aasen, Ailo; Banasiak, Krzysztof; Herlyng, Halvor; Hafner, Armin (Peer reviewed; Journal article, 2022)The ejector is a process equipment frequently used in refrigeration processes. There is currently a knowledge gap on the efficiency of ejectors operating with mixtures. To address this knowledge gap, we present a one-dimensional ... -
Optimization of Pipe Geometries with Entropy Production Minimization in Viscous Flow
Herlyng, Halvor (Master thesis, 2022)Hvordan termodynamiske irreversibiliteter i strømningen i ejektorer kan reduseres og hvordan optimalt design av ejektorer skal utføres er enda ikke helt forstått. Ejektorer er utstyr som brukes i forskjellige energiprosesser ... -
Phase transitions in multicomponent systems at the nano-scale: the existence of a minimal bubble size
Wilhelmsen, Øivind; Bedeaux, Dick; Kjelstrup, Signe; Reguera, David (Journal article; Peer reviewed, 2014)The formation of nanoscale droplets/bubbles from a metastable bulk phase is still connected to many unresolved scientific questions. In this work we analyze the stability of multicomponent liquid droplets and bubbles in ... -
Reducing the exergy destruction in the cryogenic heat exchangers of hydrogen liquefaction processes
Wilhelmsen, Øivind; Berstad, David Olsson; Aasen, Ailo; Nekså, Petter; Skaugen, Geir (Journal article; Peer reviewed, 2018)A present key barrier for implementing large-scale hydrogen liquefaction plants is their high power consumption. The cryogenic heat exchangers are responsible for a significant part of the exergy destruction in these plants ... -
Selective recovery of silver ions from copper-contaminated effluents using electrodialysis
Zimmermann, Pauline; Wahl, Kristin; Tekinalp, Önder; Solberg, Simon Birger Byremo; Deng, Liyuan; Wilhelmsen, Øivind; Burheim, Odne Stokke (Journal article; Peer reviewed, 2024)With the growing demand for silver, the recycling of this precious metal from secondary sources has become imperative. However, the presence of copper impurities poses a significant challenge. This study aims to explore ... -
Small Size Effects in Open and Closed Systems: What Can We Learn from Ideal Gases about Systems with Interacting Particles?
Bråten, Vilde; Bedeaux, Dick; Wilhelmsen, Øivind; Schnell, Sondre Kvalvåg (Peer reviewed; Journal article, 2021)Small systems have higher surface area-to-volume ratios than macroscopic systems. The thermodynamics of small systems therefore deviates from the description of classical thermodynamics. One consequence of this is that ... -
The State of Minimum Entropy Production in Hydrogen Liquefaction
Hånde, Ragnhild Aaraas (Master thesis, 2018)The main object of this thesis is to understand how to improve the hydrogen liquefaction process, by studying energy efficient heat exchanger design. This study is limited to the low temperature cooling (cryogenic cooling) ... -
Steady-State Two-Phase Flow of Compressible and Incompressible Fluids in a Capillary Tube of Varying Radius
Cheon, Hyejeong; Fyhn, Hursanay; Hansen, Alex; Wilhelmsen, Øivind; Sinha, Santanu (Peer reviewed; Journal article, 2023)We study immiscible two-phase flow of a compressible and an incompressible fluid inside a capillary tube of varying radius under steady-state conditions. The incompressible fluid is Newtonian and the compressible fluid is ... -
Structural, Mechanical, Electronic and Thermodynamic Analysis of Calcium Aluminum Silicate Crystalline Phases in Stone Wool Insulation Materials: A first-principles study
Ho, Thi H.; Ha, Do Tuong; Hoang, Nguyen-Hieu; Wilhelmsen, Øivind; Trinh, Thuat (Peer reviewed; Journal article, 2023)Stone wool materials have gained considerable attention due to their effectiveness as thermal and acoustic insulation solutions. The comprehension of crystal structure properties is pivotal in determining the overall ... -
A systematic non-equilibrium thermodynamics approach for assessing transport mechanisms in membrane distillation
Kristiansen, Kim Roger; Wilhelmsen, Øivind; Kjelstrup, Signe (Peer reviewed; Journal article, 2023)Membrane distillation (MD) is a promising technique for purifying volatile liquids at temperatures below their boiling points. This study presents a systematic non-equilibrium thermodynamics (NET) approach for analysis of ... -
Temperature anisotropy at equilibrium reveals nonlocal entropic contributions to interfacial properties
Wilhelmsen, Øivind; Trinh, Thuat; Lervik, Anders (Journal article, 2018)Density gradient theory for fluids has played a key role in the study of interfacial phenomena for a century. In this work, we revisit its fundamentals by examining the vapor-liquid interface of argon, represented by the ...