Blar i NTNU Open på forfatter "Kjelstrup, Signe"
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Non-equilibrium thermodynamics and nature-inspired chemical engineering applied to PEM fuel cells
Sauermoser, Marco (Doctoral theses at NTNU;2021:38, Doctoral thesis, 2021)The first objective of this thesis is to discover potentials for the optimisation of the performance of polymer electrolyte membrane (PEM) fuel cells by using new designs for the flow field plates (FFP) based on nature-inspired ... -
Non-equilibrium thermodynamics as a tool to compute temperature at the catalyst surface
Cruz, Carolina; Barragán, Daniel; Magnanelli, Elisa; Lervik, Anders; Kjelstrup, Signe (Journal article; Peer reviewed, 2019)The surface temperature is computed for a heterogeneous catalytic reaction model, namely the oxidation of carbon monoxide on platinum. The surface temperature was found using non-equilibrium thermodynamic theory, a theory ... -
Non-isothermal transport of multi-phase fluids in porous media. Constitutive equations
Kjelstrup, Signe; Bedeaux, Dick; Hansen, Alex; Hafskjold, Bjørn; Galteland, Olav (Journal article; Peer reviewed, 2019)We define a representative elementary volume of a porous medium in terms of lumped extensive variables, including properties of homogeneous phases, interfaces, and contact lines. Using the grand potential, we define the ... -
Non-isothermal transport of multi-phase fluids in porous media; The entropy production
Kjelstrup, Signe; Bedeaux, Dick; Hansen, Alex; Hafskjold, Bjørn; Galteland, Olav (Journal article; Peer reviewed, 2018)We derive the entropy production for transport of multi-phase fluids in a non-deformable, porous medium exposed to differences in pressure, temperature, and chemical potentials. Thermodynamic extensive variables on the ... -
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 ... -
Numerical modelling of distinct ice lenses in frost heave
Ghoreishian Amiri, Seyed Ali; Grimstad, Gustav; Gao, Hao; Kjelstrup, Signe (Peer reviewed; Journal article, 2021)Frost heave happens when three conditions coincide: the temperature is below the normal freezing point of bulk water, the sub-cooled water is connected to a water reservoir, and the mechanical conditions of the soil allows ... -
On the relation between the Langmuir and thermodynamic flux equations
van Erp, Titus Sebastiaan; Trinh, Thuat; Kjelstrup, Signe; Glavatskiy, Kirill (Journal article; Peer reviewed, 2014-01-22)Despite its approximative nature, the Langmuir theory has shown to be a very successful approach to describe experimental adsorption isotherms. Langmuir kinetics is based on systems of non-interacting particles that can ... -
Onsager-symmetry obeyed in athermal mesoscopic systems: Two-phase flow in porous media
Winkler, Mathias; Gjennestad, Magnus Aashammer; Bedeaux, Dick; Kjelstrup, Signe; Cabriolu, Raffaela; Hansen, Alex (Peer reviewed; Journal article, 2020)We compute the fluid flow time correlation functions of incompressible, immiscible two-phase flow in porous media using a 2D network model. Given a properly chosen representative elementary volume, the flow rate distributions ... -
Peltier effects in lithium-ion battery modeling
Spitthoff, Lena; Gunnarshaug, Astrid Fagertun; Bedeaux, Dick; Burheim, Odne Stokke; Kjelstrup, Signe (Peer reviewed; Journal article, 2021)A high battery temperature has been shown to be critical for lithium-ion batteries in terms of performance, degradation, and safety. Therefore, a precise knowledge of heat sources and sinks in the battery is essential. We ... -
Perspectives on Thermoelectric Energy Conversion in Ion-Exchange Membranes
Barragán, V. María; Kristiansen, Kim; Kjelstrup, Signe (Journal article; Peer reviewed, 2018)By thermoelectric power generation we mean the creation of electrical power directly from a temperature gradient. Semiconductors have been mainly used for this purpose, but these imply the use of rare and expensive materials. ... -
Phase Diagram of Methane and Carbon Dioxide Hydrates Computed by Monte Carlo Simulations
Waage, Magnus Heskestad; Vlugt, Thijs J.H.; Kjelstrup, Signe (Journal article, 2017)Molecular Monte Carlo simulations are used to compute the three-phase (hydrate–liquid water–gas) equilibrium lines of methane and carbon dioxide hydrates, using the Transferable Potentials for Phase Equilibria model for ... -
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 ... -
Pressures Inside a Nano-Porous Medium. The Case of a Single Phase Fluid
Galteland, Olav; Bedeaux, Dick; Hafskjold, Bjørn; Kjelstrup, Signe (Journal article; Peer reviewed, 2019)We define the pressure of a porous medium in terms of the grand potential and compute its value in a nano-confined or nano-porous medium, meaning a medium where thermodynamic equations need be adjusted for smallness. On ... -
Pressures inside a nano-porous medium. The case of a single phase fluid
Galteland, Olav; Kjelstrup, Signe; Bedeaux, Dick (Research report, 2018)We define the pressure of a porous medium in terms of the grand potential, and compute its value in a nano-confined or nano-porous medium, meaning a medium where thermodynamic equations need be adjusted for smallness. On ... -
Reversible heat effects of lithium metal- and porous lithium iron phosphate electrodes
Gunnarshaug, Astrid Fagertun; Burheim, Odne Stokke; Kjelstrup, Signe (Peer reviewed; Journal article, 2023)We report Peltier heats and reaction entropy of cells with lithium metal- and near fully lithiated lithium iron phosphate (LFP) electrodes. The Peltier heats were measured through the Seebeck coefficient of thermogalvanic ... -
Review - Reversible heat effects in cells relevant for lithium-ion batteries
Gunnarshaug, Astrid Fagertun; Vie, Preben Joakim Svela; Kjelstrup, Signe (Peer reviewed; Journal article, 2021)We review measurements of reversible heat effects in lithium-ion batteries, i.e. entropy changes and Seebeck coefficients of cells with relevant electrodes. We show how to compute the Peltier heat of battery electrodes ... -
Scaling factors for channel width variations in tree-like flow field patterns for polymer electrolyte membrane fuel cells - An experimental study
Sauermoser, Marco; Pollet, Bruno; Kizilova, Nataliya; Kjelstrup, Signe (Peer reviewed; Journal article, 2021)To have a uniform distribution of reactants is an advantage to a fuel cell. We report results for such a distributor with tree-like flow field plates (FFP). Numerical simulations have shown that the width scaling parameters ... -
Seebeck and Peltier coefficients of hydrogen electrodes related to the PEMFC
Zefaniya, Papy (Master thesis, 2012)The coefficient of Thermoelectric power of hydrogen electrode as function of partial pressure has shownto be negative in accordance with the negative sign of state function of entropy with a deviation of almost halfits ... -
Seebeck coefficients of cells with lithium carbonate and gas electrodes
Børset, Marit Takla; Kang, Xue; Burheim, Odne Stokke; Haarberg, Geir Martin; Xu, Q.; Kjelstrup, Signe (Journal article; Peer reviewed, 2015)The Seebeck coefficient is reported for thermoelectric cells with gas electrodes and a molten electrolyte of one salt, lithium carbonate, at an average temperature of 750 °C. We show that the coefficient, which is 0.88 mV ... -
Seebeck coefficients of cells with molten carbonates relevant for the metallurgical industry
Kang, X.; Børset, Marit Takla; Burheim, Odne Stokke; Haarberg, Geir Martin; Xu, Q.; Kjelstrup, Signe (Journal article; Peer reviewed, 2015)We report Seebeck coefficients of electrochemical cells with molten carbonate mixtures as electrolytes and carbon dioxide|oxygen electrodes. The system is relevant for use of waste heat and off-gases with concentration of ...