Thermo

15 pages, 2445 KiB

Open AccessArticle

Ergodic Algorithmic Model (EAM), with Water as Implicit Solvent, in Chemical, Biochemical, and Biological Processes

by Emilia Fisicaro, Carlotta Compari and Antonio Braibanti

Thermo 2021, 1(3), 361-375; https://doi.org/10.3390/thermo1030022 - 30 Nov 2021

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For many years, we have devoted our research to the study of the thermodynamic properties of hydrophobic hydration processes in water, and we have proposed the Ergodic Algorithmic Model (EAM) for maintaining the thermodynamic properties of any hydrophobic hydration reaction at a constant pressure from the experimental determination of an equilibrium constant (or other potential functions) as a function of temperature. The model has been successfully validated by the statistical analysis of the information elements provided by the EAM model for about fifty compounds. The binding functions are convoluted functions, RlnK_eq = {f(1/T)* g(T)} and RTlnK_eq = {f(T)* g(lnT)}, where the primary linear functions f(1/T) and f(T) are modified and transformed into parabolic curves by the secondary functions g(T) and g(lnT), respectively. Convoluted functions are consistent with biphasic dual-structure partition function, {DS-PF} = {M-PF} ∙ {T-PF} ∙ {ζ_w}, composed by ({M-PF} (Density Entropy), {T-PF}) (Intensity Entropy), and {ζ_w} (implicit solvent). In the present paper, after recalling the essential aspects of the model, we outline the importance of considering the solvent as “implicit” in chemical and biochemical reactions. Moreover, we compare the information obtained by computer simulations using the models till now proposed with “explicit” solvent, showing the mess of information lost without considering the experimental approach of the EAM model. Full article

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29 pages, 15024 KiB

Open AccessReview

In-Process Monitoring of Temperature Evolution during Fused Filament Fabrication: A Journey from Numerical to Experimental Approaches

by Hamid Reza Vanaei, Mohammadali Shirinbayan, Michael Deligant, Sofiane Khelladi and Abbas Tcharkhtchi

Thermo 2021, 1(3), 332-360; https://doi.org/10.3390/thermo1030021 - 27 Oct 2021

Cited by 39 | Viewed by 6593

Abstract

Fused filament fabrication (FFF), an additive manufacturing technique, unlocks alternative possibilities for the production of complex geometries. In this process, the layer-by-layer deposition mechanism and several heat sources make it a thermally driven process. As heat transfer plays a particular role and determines the temperature history of the merging filaments, the in-process monitoring of the temperature profile guarantees the optimization purposes and thus the improvement of interlayer adhesion. In this review, we document the role of heat transfer in bond formation. In addition, efforts have been carried out to evaluate the correlation of FFF parameters and heat transfer and their effect on part quality. The main objective of this review paper is to provide a comprehensive study on the in-process monitoring of the filament’s temperature profile by presenting and contributing a comparison through the literature. Full article

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35 pages, 6321 KiB

Open AccessArticle

Thermal Properties and Behaviour of Am-Bearing Fuel in European Space Radioisotope Power Systems

by Emily Jane Watkinson, Ramy Mesalam, Jean-François Vigier, Ondřej Beneš, Jean-Christophe Griveau, Eric Colineau, Mark Sierig, Daniel Freis, Richard M. Ambrosi, Dragos Staicu and Rudy J. M. Konings

Thermo 2021, 1(3), 297-331; https://doi.org/10.3390/thermo1030020 - 15 Oct 2021

Cited by 8 | Viewed by 4046

Abstract

The European Space Agency is funding the research and development of ²⁴¹Am-bearing oxide-fuelled radioisotope power systems (RPSs) including radioisotope thermoelectric generators (RTGs) and European Large Heat Sources (ELHSs). The RPSs’ requirements include that the fuel’s maximum temperature, T_max, must remain below its melting temperature. The current prospected fuel is (Am_0.80U_0.12Np_0.06Pu_0.02)O_1.8. The fuel’s experimental heat capacity, C_p, is determined between 20 K and 1786 K based on direct low temperature heat capacity measurements and high temperature drop calorimetry measurements. The recommended high temperature equation is C_p(T/K) = 55.1189 + 3.46216 × 10² T − 4.58312 × 10⁵ T⁻² (valid up to 1786 K). The RTG/ELHS T_max is estimated as a function of the fuel thermal conductivity, k, and the clad’s inner surface temperature, T_{i cl}, using a new analytical thermal model. Estimated bounds, based on conduction-only and radiation-only conditions between the fuel and clad, are established. Estimates for k (80–100% T.D.) are made using C_p, and estimates of thermal diffusivity and thermal expansion estimates of americium/uranium oxides. The lowest melting temperature of americium/uranium oxides is assumed. The lowest k estimates are assumed (80% T.D.). The highest estimated T_max for a ‘standard operating’ RTG is 1120 K. A hypothetical scenario is investigated: an ELHS T_{i cl} = 1973K-the RPSs’ requirements’ maximum permitted temperature. Fuel melting will not occur. Full article

(This article belongs to the Special Issue Thermodynamics and Nuclear Materials)

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11 pages, 2166 KiB

Open AccessArticle

Study of Thermodynamic Modeling of Isothermal and Isobaric Binary Mixtures in Vapor-Liquid Equilibrium (VLE) of Tetrahydrofuran with Benzene (303.15 K) Cyclohexane (333.15 K), Methanol (103 kPa), and Ethanol (100 kPa)

by Leonardo Steyman Reyes Fernández, Eliseo Amado-Gonzaléz and Erik Germán Yanza Hurtado

Thermo 2021, 1(3), 286-296; https://doi.org/10.3390/thermo1030019 - 11 Oct 2021

Cited by 1 | Viewed by 5991

Abstract

Tetrahydrofuran (THF) is an aprotic solvent with multiple applications in diverse areas of chemical, petrochemical, and pharmaceutical industries with an important impact in chemical waste liquid with other solvents. In this work, 51 available VLE data, for isothermal binary mixtures of THF(1) + Benzene(2) and THF(1) + Cyclohexane(2) at 303.15 and 333.15 K, respectively, and isobaric THF(1) + Methanol(2) at 103 kPa and THF(1) + Ethanol(2) at 100 kPa were used in the development of the activity coefficient models. The quality of experimental data was checked using the Herington test. VLE binary data was correlated with models Wilson, NRTL UNIQUAC, and UNIFAC to obtain binary parameters and activity coefficients. The best thermodynamic consistency when conducting the Herington test for the VLE data was found for the THF(1) +Cyclohexane(2) isothermal system and THF(1) + Ethanol(2) isobaric system. The UNIQUAC model for isothermal systems THF(1) + Benzene(2) and THF(1) + Cyclohexane(2), the NRTL model for the isobaric system THF(1) + Methanol(2), and the UNIQUAC model for THF(1) + Ethanol(2) perform better than the other models. Full article

(This article belongs to the Special Issue Vapor–Liquid Equilibrium and Chemical Thermodynamics)

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Thermo, Volume 1, Issue 3 (December 2021) – 4 articles

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