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- Hasan, A.M. (author), Larsson, Johan (author), Pirozzoli, Sergio (author), Pecnik, Rene (author) journal article 2024
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Zhao, A. (author), Pecnik, Rene (author), Peeters, J.W.R. (author)Heating in industrial processes is responsible for approximately 13% of greenhouse gas emissions in Europe. Switching from fossil-fuel based boilers to heat pumps can help mitigate the effect of global warming. The present work proposes novel high-temperature transcritical heat pump cycles targeted at heating air with a mass flow rate of 10...journal article 2024
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Bugeat, B. (author), Boldini, P.C. (author), Hasan, A.M. (author), Pecnik, Rene (author)This paper addresses the stability of plane Couette flow in the presence of strong density and viscosity stratifications. It demonstrates the existence of a generalised inflection point that satisfies the generalised Fjørtoft criterion of instability when a minimum of kinematic viscosity is present in the base flow. The characteristic scales...journal article 2024
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Nederstigt, P. (author), Pecnik, Rene (author)Isentropic processes in thermodynamics are fundamental to our understanding of numerous physical phenomena across different scientific and engineering fields. They provide a theoretical reference case for the evaluation of real thermodynamic processes and observations. Yet, as analytical relations for isentropic transformations in gas dynamics...journal article 2023
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Bianchi, Giuseppe (author), Brillert, Dieter (author), Christodoulides, Paul (author), Pecnik, Rene (author), Kalogirou, Soteris (author)Editorialcontribution to periodical 2023
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Hasan, A.M. (author), Larsson, Johan (author), Pirozzoli, Sergio (author), Pecnik, Rene (author)A transformation that relates a compressible wall-bounded turbulent flow with nonuniform fluid properties to an equivalent incompressible flow with uniform fluid properties is derived and validated. The transformation accounts for both variable-property and intrinsic compressibility effects, the latter being the key improvement over the...journal article 2023
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Agostinho, Luewton L.F. (author), Pecnik, Rene (author), Woisetschläger, Jakob (author), de Kroon, Esther (author), Şişcanu, Nicolae (author), van de Griend, Maarten V. (author), Loiskandl, Willibald (author), Fuchs, Elmar C. (author)There was an omission in the original publication [1]. The authors showed SOTR values in a figure but did not mention how these values were calculated. As a consequence, the calculations based upon the SOTR also need to be more specific, which is why “the twisted regime of” has been added in front of “the hyperbolic funnel”. An addition has...journal article 2023
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Draškić, M. (author), Bugeat, B. (author), Pecnik, Rene (author)The steady state behavior of thermodynamically supercritical natural circulation loops (NCLs) is investigated in this work. Experimental steady state results with supercritical carbon dioxide are presented for reduced pressures in the range of 1.1-1.5, and temperatures in the range of 20-65 <sup>◦</sup>C. Distinct thermodynamic states are...journal article 2023
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Diez Sanhueza, R.G. (author), Smit, S.H.H.J. (author), Peeters, J.W.R. (author), Pecnik, Rene (author)This paper presents a machine learning methodology to improve the predictions of traditional RANS turbulence models in channel flows subject to strong variations in their thermophysical properties. The developed formulation contains several improvements over the existing Field Inversion Machine Learning (FIML) frameworks described in the...journal article 2023
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Bugeat, B. (author), Boldini, P.C. (author), Pecnik, Rene (author)Ren et al. (2019) recently studied the stability of the boundary layer flow over a flat plate for supercritical CO2. While only one unstable mode usually exists for boundary layer flows, the authors found an additional unstable mode, whose origin has so far not been identified. In the present work, we carry out a stability analysis in the...conference paper 2022
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Agostinho, Luewton L.F. (author), Pecnik, Rene (author), Woisetschläger, Jakob (author), de Kroon, Esther (author), Şişcanu, Nicolae (author), van de Griend, Maarten V. (author), Loiskandl, Willibald (author), Fuchs, Elmar C. (author)Aeration is one of the most cost intensive steps in water and wastewater treatment due to the large energy requirement for the creation of large surfaces for sufficient gas exchange as well as for providing efficient liquid transport in order to exchange saturated liquid elements at the surface with unsaturated ones from the bulk. In this...journal article 2022
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Fuchs, Elmar C. (author), Woisetschläger, Jakob (author), Wexler, Adam D. (author), Pecnik, Rene (author), Vitiello, Giuseppe (author)A horizontal electrohydrodynamic (EHD) liquid bridge (also known as a “floating water bridge”) is a phenomenon that forms when high voltage DC (kV·cm<sup>-1</sup>) is applied to pure water in two separate beakers. The bridge, a free-floating connection between the beakers, acts as a cylindrical lens and refracts light. Using an...journal article 2021
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Silvestri, S. (author), Pecnik, Rene (author)We present direct numerical simulations of developing turbulent channel flows subjected to thermal expansion or contraction downstream of a heated or cooled wall. Using different constitutive relations for viscosity we analyse the response of variable property flows to streamwise acceleration/deceleration by separating the effect of...journal article 2021
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Silvestri, S. (author), Roekaerts, D.J.E.M. (author), Pecnik, Rene (author)The present work investigates the modeling of turbulent heat transfer in flows where radiative and convective heat transfer are coupled. In high temperature radiatively participating flows, radiation is the most relevant heat transfer mechanism and, due to its non-locality, it causes counter intuitive interactions with the turbulent...journal article 2021
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Hirai, Ryo (author), Pecnik, Rene (author), Kawai, Soshi (author)In supersonic turbulent boundary layers over isothermal walls, we investigate how the wall heat flux affects turbulent statistics and velocity scaling laws. To distinguish local Reynolds number and compressibility effects, we consider a conventional ideal gas with Sutherland's law and a fluid for which the dynamic viscosity is proportional to...journal article 2021
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Otero Rodriguez, G.J. (author), Smit, S.H.H.J. (author), Pecnik, Rene (author)Organic Rankine cycle (ORC) systems are a readily available technology to convert thermal energy from renewable- and waste heat sources into electricity. However, their thermal performance is relatively low due to the low temperature of the available heat sources, but more importantly, due to the low efficiency of the employed expander....journal article 2021
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Schöffer, S.I. (author), Klein, S.A. (author), Aravind, P.V. (author), Pecnik, Rene (author)New technologies are being developed to produce electricity cleaner and more efficient. Promising technologies among these are the solid oxide fuel cell and the supercritical carbon dioxide Brayton cycle. This study investigates the potential of integrating both technologies. The solid oxide fuel cell is known as a potentially clean and...journal article 2021
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Ren, J. (author), Marxen, Olaf (author), Pecnik, Rene (author)We investigate the hydrodynamic stability of compressible boundary layers over adiabatic walls with fluids at supercritical pressure in the proximity of the Widom line (also known as the pseudo-critical line). Depending on the free-stream temperature and the Eckert number that determines the viscous heating, the boundary-layer temperature...journal article 2019
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Ren, J. (author), Fu, Song (author), Pecnik, Rene (author)The objective of this work is to investigate linear modal and algebraic instability in Poiseuille flows with fluids close to their vapour-liquid critical point. Close to this critical point, the ideal gas assumption does not hold and large non-ideal fluid behaviours occur. As a representative non-ideal fluid, we consider supercritical carbon...journal article 2019
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Silvestri, S. (author), Pecnik, Rene (author)We implemented a fast Reciprocal Monte Carlo algorithm to accurately solve radiative heat transfer in turbulent flows of non-grey participating media that can be coupled to fully resolved turbulent flows, namely to Direct Numerical Simulation (DNS). The spectrally varying absorption coefficient is treated in a narrow-band fashion with a...journal article 2019