Thermo

21 pages, 2656 KB

Open AccessArticle

Modeling the Thermomechanical Characteristics of a Heat-Insulated Rod with a Variable Cross-Section

by Anarbay Kudaykulov, Azat Tashev, Bagdat Teltayev and Aizhan Muta

Thermo 2026, 6(1), 2; https://doi.org/10.3390/thermo6010002 (registering DOI) - 26 Dec 2025

In this study, the thermomechanical behavior of a variable cross-section rod with fixed ends is studied using an analytical method. A rod with a radius that varies quadratically with length is considered, and it is thermally insulated on its side surface. Heat flow [...] Read more.

In this study, the thermomechanical behavior of a variable cross-section rod with fixed ends is studied using an analytical method. A rod with a radius that varies quadratically with length is considered, and it is thermally insulated on its side surface. Heat flow is applied to the left end of the rod, and heat exchange with the environment occurs at the right end. Based on the obtained temperature distribution, the thermal strains, stresses, displacements, and total elongation are determined. The results highlight the influence of boundary thermal conditions on the thermomechanical response of the rod, which is of interest for the design and analysis of structural elements operating under conditions of uneven thermal stress. Full article

21 pages, 5888 KB

Open AccessArticle

Performance Enhancement of Latent Heat Storage Using Extended-Y-Fin Designs

by Aurang Zaib, Abdur Rehman Mazhar, Cheng Zeng, Tariq Talha and Hasan Aftab Saeed

Thermo 2026, 6(1), 1; https://doi.org/10.3390/thermo6010001 (registering DOI) - 26 Dec 2025

Abstract

The low thermal conductivity of phase-change materials (PCMs) remains a key limitation in latent heat thermal energy storage systems, leading to slow melting and incomplete energy recovery. To address this challenge, this study explores extended Y-Fin geometries as a novel heat transfer enhancement [...] Read more.

The low thermal conductivity of phase-change materials (PCMs) remains a key limitation in latent heat thermal energy storage systems, leading to slow melting and incomplete energy recovery. To address this challenge, this study explores extended Y-Fin geometries as a novel heat transfer enhancement strategy within a concentric-tube latent heat thermal energy storage configuration. Six fin designs, derived from a baseline Y-shaped structure, were numerically compared to assess their influence on the melting and solidification behavior of stearic acid. A two-dimensional transient enthalpy–porosity model was developed and rigorously verified through grid, temporal, and residual convergence analyses. The results indicate that fin geometry plays a critical role in enhancing heat transfer within the PCM domain. The extended Y-Fin configuration achieved the fastest melting time, 28% shorter than the baseline Y-Fin case, due to improved thermal penetration and bottom-region accessibility. Additionally, the thermal performance was evaluated using nano-enhanced PCMs (10% Al₂O₃ and CuO in stearic acid) and paraffin wax. The addition of Al₂O₃ nanoparticles significantly improved thermal conductivity, while paraffin wax exhibited the shortest melting duration due to its lower melting point and latent heat. This study introduces an innovative fin architecture combining extended conduction paths and improved convective reach for efficient latent heat storage systems. Full article

(This article belongs to the Special Issue Advances in Latent Thermal Energy Storage: Materials, Modeling, and System Integration)

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23 pages, 3084 KB

Open AccessArticle

Density and Viscosity of Orange Oil, Turpentine, and Their Hydrogenated Derivatives as Biofuel Components

by Brent Mellows and Yolanda Sanchez-Vicente

Thermo 2025, 5(4), 59; https://doi.org/10.3390/thermo5040059 - 16 Dec 2025

Abstract

Biofuels represent a viable alternative to fossil fuels due to their lower greenhouse gas emissions, potential for large-scale production, and renewable nature. Orange oil, turpentine, and their hydrogenated derivatives have emerged as promising candidates for biofuel components. Efficient design and operation of internal [...] Read more.

Biofuels represent a viable alternative to fossil fuels due to their lower greenhouse gas emissions, potential for large-scale production, and renewable nature. Orange oil, turpentine, and their hydrogenated derivatives have emerged as promising candidates for biofuel components. Efficient design and operation of internal combustion engines require knowledge of biofuel density and viscosity as functions of temperature; however, experimental data on these properties remain limited. In this work, the densities and viscosities of turpentine, orange oil, hydrogenated turpentine, and hydrogenated orange oil were measured at atmospheric pressure over the temperature range (293.15–373.15) K. The measurements were performed with uncertainties below 0.05 kg·m⁻³ for density and 0.3 mPa·s for viscosity. The experimental data were correlated as a function of temperature using a quadratic function for density and the Andrade equation for viscosity, with absolute average relative deviations of 0.01% for density and 0.5% for viscosity. For all substances, both viscosity and density decrease with increasing temperature, and they are lower than the values for biodiesel. Orange oil and turpentine exhibited higher densities but lower viscosities than their hydrogenated counterparts, which can be attributed to differences in molecular size and packing efficiency. Finally, the measured density and viscosity values are compared with the limit values specified in the European and American biodiesel standards. The analysis shows that blending these essential oils with conventional biodiesel could result in biofuel mixtures that meet both standards. Full article

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25 pages, 1454 KB

Open AccessArticle

Improving the Efficiencies of Copper Pyrometallurgy Through Exergy Assessment

by Diana Marel Ruiz-Ruiz, Luis Jesús Ramírez-Ramírez, Aarón Almaraz-Gómez, Ayrton Homero Bautista-Aguilar, José Guadalupe Chacón-Nava and Gabriel Plascencia

Thermo 2025, 5(4), 58; https://doi.org/10.3390/thermo5040058 - 13 Dec 2025

Abstract

To satisfy the needs of an ever-growing population, it is imperative to cope with the extended demand for copper. To do so, copper makers mostly rely on pyrometallurgical processes that are characterized by emitting hazardous gases and solid wastes, and by the fact [...] Read more.

To satisfy the needs of an ever-growing population, it is imperative to cope with the extended demand for copper. To do so, copper makers mostly rely on pyrometallurgical processes that are characterized by emitting hazardous gases and solid wastes, and by the fact that these processes are energy demanding. Additionally, copper makers face the issue of processing leaner ore bodies or exploiting mineral deposits already overexploited or about to end their productivity cycle. These problems compromise the sustainable production of copper. Because of that, this study focuses on the leading technology in use to assess and identify possible solutions in order to improve the efficiency of energy usage and to decrease the amount of wastes generated in copper pyrometallurgy. To do so, reliable thermodynamic databases and Sankey diagrams were used to determine possible improvements. For example, it is determined that by increasing the mass ratio of Fe/Cu in the mineral feedstock may result in increasing the copper content in the matte, and thus reducing the exergy flows, resulting in improved energy usage. Another positive impact is that using oxygen-enriched air with higher copper concentrations could decrease SO₂ emissions by nearly 25%. Among other detrimental environmental issues, they entail. Full article

(This article belongs to the Special Issue Thermal Science and Metallurgy)

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24 pages, 5810 KB

Open AccessArticle

Experimental–Numerical Investigation of Natural Convection from a Plate Fin Heat Sink with Correlation Assessment

by Mateo Kirinčić, Tin Fadiga and Boris Delač

Thermo 2025, 5(4), 57; https://doi.org/10.3390/thermo5040057 - 5 Dec 2025

Abstract

This study investigates the thermal performance of a passive vertical aluminum heat sink with plate fins through combined experimental measurements and numerical simulations. Using a custom-made experimental apparatus which used water as the heat source, heat transfer rate was determined, and heat transfer [...] Read more.

This study investigates the thermal performance of a passive vertical aluminum heat sink with plate fins through combined experimental measurements and numerical simulations. Using a custom-made experimental apparatus which used water as the heat source, heat transfer rate was determined, and heat transfer coefficient was compared against established empirical correlations, demonstrating good agreement. A 3D steady-state mathematical model was developed to capture the conjugate heat transfer problem of conduction and natural convection, with buoyancy-driven airflow modeled with the incompressible ideal gas law. The problem was solved numerically using the finite volume method through ANSYS Fluent 18.2 solver and validated against experimental data and analytical correlations, exhibiting good agreement throughout. Parametric analysis followed, investigating the influence of various base (50, 65, 80 °C) and ambient (19, 24, 29 °C) temperatures, resulting in base-to-ambient temperature differences from 21 to 61 °C. Increasing this temperature difference led to a significant increase in heat transfer rate, while heat transfer coefficient increased and overall thermal resistance decreased moderately. Additionally, a Nusselt–Rayleigh (Nu–Ra) number correlation, consistent with ranges reported in the literature, was derived, providing the scaling to predict the thermal performance of similar natural convection-governed heat sinks. The validated computational methodology, combined with obtained experimental and numerical results, presents a foundation for future studies focused on more complex heat sink geometries and physics. Full article

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16 pages, 847 KB

Open AccessArticle

Dynamic Vapor Sorption (DVS) Analysis of the Thermo-Hygroscopic Behavior of Arthrospira platensis Under Varying Environmental Conditions

by Thouraya Ghnimi, Lamine Hassini and Mohamed Bagane

Thermo 2025, 5(4), 56; https://doi.org/10.3390/thermo5040056 - 2 Dec 2025

Abstract

This paper presents a new study and analysis of the thermo-hygroscopic behavior of Arthrospira platensis using dynamic vapor sorption (DVS) system. Thermo-hygroscopic characterization is essential for optimizing the drying process and enhancing storage conditions. Therefore, the objective of this work was to investigate [...] Read more.

This paper presents a new study and analysis of the thermo-hygroscopic behavior of Arthrospira platensis using dynamic vapor sorption (DVS) system. Thermo-hygroscopic characterization is essential for optimizing the drying process and enhancing storage conditions. Therefore, the objective of this work was to investigate the thermo-hygroscopic properties of Arthrospira (Spirulina) platensis using a dynamic vapor sorption (DVS) system. This thermo-hygroscopic analysis focused on three fundamental parameters, namely: the desorption isotherms, the net isosteric heat of water desorption, and the moisture diffusivity. Desorption isotherms were measured at five different temperatures (25 °C, 40 °C, 50 °C, 60 °C and 80 °C) over a relative humidity range of 10–80%. The desorption isotherm data were fitted to five semi-empirical models: GAB, Oswin, Smith, Henderson, and Peleg. The results indicated that the GAB model provided the best fit for the experimental data. The net isosteric heat of desorption was determined using the Clausius–Clapeyron relation. It decreased from 21.3 to 4.29 KJ/mol as the equilibrium moisture content increased from 0.02 to 0.1 Kg/Kg (dry basis). Additionally, the moisture diffusivity of Arthrospira platensis was estimated based on Fick’s second law of diffusion and the desorption kinetics obtained from the DVS equipment. This parameter varied between 1.04 10⁻⁸ m²/s and 1.46 10⁻⁷ m²/s for average moisture contents ranging from 0.003 Kg/Kg to 0.191 Kg/Kg (dry basis). Furthermore, the activation energy for desorption was estimated to be approximately 33.7 KJ/mol. Full article

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14 pages, 11735 KB

Open AccessArticle

Mesoscale Insights into Convective Heat Transfer in Concentric Cylinder Systems

by Thorstein Wang, Zhiliang Zhang and Jianying He

Thermo 2025, 5(4), 55; https://doi.org/10.3390/thermo5040055 - 24 Nov 2025

Abstract

As devices and systems shrink in size, understanding heat transfer at the mesoscopic scale becomes increasingly critical for the design of efficient thermal management strategies. This study investigates convective heat transfer in concentric cylinders, a geometry which is relevant to small-scale technologies. Finite [...] Read more.

As devices and systems shrink in size, understanding heat transfer at the mesoscopic scale becomes increasingly critical for the design of efficient thermal management strategies. This study investigates convective heat transfer in concentric cylinders, a geometry which is relevant to small-scale technologies. Finite elements simulation are used to examine the influence of geometry and temperature on effective thermal conductivity, and on a parameter introduced as the apparent heat transfer coefficient. It is found that the effective thermal conductivity goes above unity for inner and outer radii at the millimeter scale, which is smaller than that predicted by the available analytical studies. This deviation is attributed to the fact that finite element simulations capture the behavior of temperature boundary layers more accurately at small scales than these analytical models. These insights aid in identifying conditions in which convection can be ignored, significantly simplifying thermal simulations. This work also reveals that at the mesoscale, the ratio between outer and inner radius for which a cylinder can be considered free-standing is much larger than at the macroscale. This highlights the importance of taking the surrounding surfaces into consideration when performing experiments on the heat transfer properties of mesoscale cylinders such as wires. Full article

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17 pages, 3848 KB

Open AccessArticle

Structural Design and Optimization of Knitted Heaters for Optimized Heat Distribution

by Beyza Bozali, Sepideh Ghodrat and Kaspar M. B. Jansen

Thermo 2025, 5(4), 54; https://doi.org/10.3390/thermo5040054 - 19 Nov 2025

Abstract

Knitted heaters have attracted significant interest due to their flexibility and ease of integration into smart textile applications. However, uneven heat distribution remains a major challenge, leading to comfort issues and inefficient energy usage. This study presents an analytical, physics-based model that links [...] Read more.

Knitted heaters have attracted significant interest due to their flexibility and ease of integration into smart textile applications. However, uneven heat distribution remains a major challenge, leading to comfort issues and inefficient energy usage. This study presents an analytical, physics-based model that links the resistance, power distribution, and surface temperature of knitted heaters to key design parameters such as size, configuration, material properties, and knitting structure to establish guidelines for achieving a desired temperature rise over a specified surface area. The model was validated experimentally across a range of heaters (3–12 lines) arranged in ladder and diagonal configurations. Results showed good agreement between predictions and measurements for higher line counts (10–12), while larger deviations occurred in smaller heaters (3–5 lines) due to contact resistance and current losses. A prototype knitted wristband demonstrated physiologically relevant heating (>33 °C) under safe, low-voltage operation. These findings provide a quantitative design framework for optimizing knitted heaters and highlight their potential for scalable integration into wearable and therapeutic applications. Full article

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18 pages, 2700 KB

Open AccessArticle

Optimization of the Performance of Double-Skin Façades Across Six Climates: Effects of Orientation, Blinds, and Overhangs on Energy Efficiency and Carbon Emissions

by Niloufar Ziasistani, Andrés Meana-Fernández and Antonio José Gutiérrez-Trashorras

Thermo 2025, 5(4), 53; https://doi.org/10.3390/thermo5040053 - 13 Nov 2025

Abstract

The building sector accounts for nearly 40% of global energy consumption and over one-third of energy-related carbon emissions. Therefore, it is vital to adopt low-carbon design strategies. Double-Skin Façades (DSFs) offer significant potential to improve energy efficiency through the dynamic control of heat [...] Read more.

The building sector accounts for nearly 40% of global energy consumption and over one-third of energy-related carbon emissions. Therefore, it is vital to adopt low-carbon design strategies. Double-Skin Façades (DSFs) offer significant potential to improve energy efficiency through the dynamic control of heat and daylight. This study evaluates the combined effects of building orientation, fixed shading devices, and adjustable blinds on the performance of DSFs across six cities representing diverse climate types: Phoenix, Stockholm, Kuala Lumpur, London, Cape Town, and Tokyo. Using a model developed in DesignBuilder, 852 scenarios were simulated with 5-min time steps over a full year. The results show that optimal orientation depends on the climate and that cooling load may be reduced up to 59%, with CO₂ emission savings up to 11.7% compared to a base south-facing configuration. External blinds outperformed internal blinds in reducing the cooling demand, reaching reductions of up to 27.7% in hot climates, though often increasing the heating load in cold climates. Combining overhangs and external blinds provided additional cooling savings in some cases but was generally less effective than external blinds alone. The findings highlight the importance of climate-specific DSF designs, with orientation and external blinds being the most effective strategies for reducing operational energy use and emissions. Full article

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15 pages, 3663 KB

Open AccessArticle

Advancing Sustainable Refrigeration: In-Depth Analysis and Application of Air Cycle Technologies

by Lorenz Hammerschmidt, Zlatko Raonic and Michael Tielsch

Thermo 2025, 5(4), 52; https://doi.org/10.3390/thermo5040052 - 12 Nov 2025

Abstract

Air cycle systems, once largely replaced by vapour-compression technologies due to efficiency concerns, are now re-emerging as a viable and sustainable alternative for highly dynamic thermal applications and excel in ultra-low temperature. By using air as the working fluid, these systems eliminate the [...] Read more.

Air cycle systems, once largely replaced by vapour-compression technologies due to efficiency concerns, are now re-emerging as a viable and sustainable alternative for highly dynamic thermal applications and excel in ultra-low temperature. By using air as the working fluid, these systems eliminate the need for synthetic refrigerants and comply naturally with evolving environmental regulations. This study presents the conceptual design and simulation-based analysis of a novel air cycle machine developed for advanced automotive testing environments. The system is intended to replicate a wide range of climatic conditions—from deep winter to peak summer—through the use of fast-responding turbomachinery and a flexible control strategy. A central focus is placed on the radial turbine, which is designed and evaluated using a modular, open source framework that integrates geometry generation, off-design CFD simulation, and performance mapping. The study outlines a potential operating strategy based on these simulations and discusses a control architecture combining lookup tables with zone-specific PID tuning. While the results are theoretical, they demonstrate the feasibility and flexibility of the proposed approach, particularly the turbine’s role within the system. Full article

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27 pages, 388 KB

Open AccessArticle

Thermodynamics and Nonlocality in Continuum Physics

by Claudio Giorgi and Angelo Morro

Thermo 2025, 5(4), 51; https://doi.org/10.3390/thermo5040051 - 9 Nov 2025

Abstract

This paper is devoted to the modelling of nonlocality in continuum physics through constitutive functions that depend on suitable gradients. For definiteness, the attention is addressed to elastic solids, heat conductors, and magnetic solids. Models are developed where both the requirements of the [...] Read more.

This paper is devoted to the modelling of nonlocality in continuum physics through constitutive functions that depend on suitable gradients. For definiteness, the attention is addressed to elastic solids, heat conductors, and magnetic solids. Models are developed where both the requirements of the second law of thermodynamics and the balance equations are satisfied for the constitutive functions that involve gradients of strain, temperature, heat flux, and magnetization. Concerning elastic and magnetic solids, it is shown that, depending on the chosen variables, the standard symmetry property of the stress holds identically. The models so developed are free from any hyperstress tensor frequently considered in the literature. Full article

16 pages, 2444 KB

Open AccessArticle

Kinetics of Complex Double Salts [Co(A)₃][Fe(C₂O₄)₃]∙xH₂O (A=2NH₃, En (Ethylenediamine))

by Alevtina Gosteva, Semen Lapuk and Alexander Gerasimov

Thermo 2025, 5(4), 50; https://doi.org/10.3390/thermo5040050 - 9 Nov 2025

Abstract

Complex compounds are under close scrutiny by scientists as precursors, which are needed to produce functional materials. When the thermolysis method of double complex salts is used on an industrial scale, the most detailed information on the thermal decomposition, including the kinetics of [...] Read more.

Complex compounds are under close scrutiny by scientists as precursors, which are needed to produce functional materials. When the thermolysis method of double complex salts is used on an industrial scale, the most detailed information on the thermal decomposition, including the kinetics of decomposition, is required. The kinetics of pyrolysis, solid, and gaseous products of [Co(NH₃)₆][Fe(C₂O₄)₃]∙2H₂O (I) and [Co(en)₃][Fe(C₂O₄)₃] (II) (en—ethylenediamine) thermolysis were studied in this work. The solid products of thermal decomposition were studied using scanning electron microscopy and elemental analysis, and the specific surface area (8 and 71 m²/g, respectively) was measured. It was determined that a double complex salt (DCS) with a coordinated en has a higher thermal stability than with NH₃ due to the chelation effect. Full article

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16 pages, 4585 KB

Open AccessArticle

Effects of Heat Input and Backing Gas on Bead Geometry and Weld Heat Tint in Sanitary Tube Welding

by Ngoc-Thien Tran, Van-Thuc Nguyen, Thanh Trung Do and Van-Sung Nguyen

Thermo 2025, 5(4), 49; https://doi.org/10.3390/thermo5040049 - 4 Nov 2025

Abstract

Heat input always plays a crucial role in enhancing penetration depth within the heat-affected zone (HAZ) of the orbital TIG welding process. The heat tint, in addition, caused by heat input, is a decisive factor for the quality of sanitary tube welds, which [...] Read more.

Heat input always plays a crucial role in enhancing penetration depth within the heat-affected zone (HAZ) of the orbital TIG welding process. The heat tint, in addition, caused by heat input, is a decisive factor for the quality of sanitary tube welds, which AWS D18.2 strictly regulates. Therefore, controlling heat input to achieve complete penetration while maintaining an acceptable heat tint level is considered essential in sanitary tube welding. For this reason, this study conducted 27 experimental welds with variations in the parameters of the Orbital TIG Welding process to determine the optimal welding parameters for sanitary tubes with an outer diameter of Ø38.1 mm and a thickness of 1.65 mm. Taguchi analysis identified the optimal parameter combination to achieve full penetration as a welding current of 100 A, an arc length of 1.5 mm, and a welding speed of 5 mm/s. In addition, the use of internal backing gas and arc time significantly improved the heat tint level of the welds produced under the proposed parameter set. Full article

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18 pages, 4457 KB

Open AccessArticle

Experimental Study on the Enhancement of Pool Boiling Heat Transfer Characteristics of Water-Based Nanofluids with Graphene Nanoplatelets on Nichrome Wire

by Srinivasan Venkatraman and Chandrasekaran Selvam

Thermo 2025, 5(4), 48; https://doi.org/10.3390/thermo5040048 - 3 Nov 2025

Abstract

The present study aims to experimentally investigate pool boiling heat transfer characteristics, such as critical heat flux (CHF) and boiling heat transfer coefficient (BHTC), of pure distilled water (d-H₂O) and functionalised graphene nanoplatelet (f-GnPs)–d-H₂O nanofluids using a nichrome (Ni-Cr) [...] Read more.

The present study aims to experimentally investigate pool boiling heat transfer characteristics, such as critical heat flux (CHF) and boiling heat transfer coefficient (BHTC), of pure distilled water (d-H₂O) and functionalised graphene nanoplatelet (f-GnPs)–d-H₂O nanofluids using a nichrome (Ni-Cr) test wire as the heating element. The distilled water (dH₂O) and GnP (5–10 nm and 15 µm, Cheap Tubes, USA) were chosen as the base fluid and nanomaterial, respectively. The GnP was chemically functionalized and dispersed in dH₂O using a probe sonicator. The nanofluids were characterized by measuring the zeta potential distribution and pH to ensure stability on day 1 and day 10 following preparation. The results show that the zeta potential values range from −31.6 mV to −30.6 mV, while the pH values range from 7.076 to 7.021 on day 1 and day 10, respectively. The novelty of the present study lies in the use of f-GnPs with a controlled size and stable nanofluid, confirmed through zeta potential and pH analysis, to determine the heat transfer behaviour of a Ni-Cr test wire under pool boiling conditions. The pool boiling heat transfer characteristics, such as CHF and BHTC, were observed using the fabricated pool boiling heat transfer test facility. Initially, the dH₂O and f-GnP–dH₂O nanofluids were separately placed in a glass container and heated using a pre-heater to reach their saturation point of 100 °C. The electrical energy was gradually increased until it reached the critical point of the Ni-Cr test wire, i.e., the burnout point, at which it became reddish-yellow hot. The CHF and BHTC were predicted from the experimental outputs of voltage and current. The results showed an enhancement of ~15% in the CHF at 0.1 vol% of f-GnPs. The present study offers a method for enhancing two-phase flow characteristics for heat pipe applications. Full article

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18 pages, 2656 KB

Open AccessArticle

Integrating Life Cycle Assessment and Response Surface Methodology for Optimizing Carbon Reduction in Coal-to-Synthetic Natural Gas Process

by Caimiao Zheng, Jianli Hao, Shiwang Yu, Luigi Di Sarno, Yuan Shi and Ji Han

Thermo 2025, 5(4), 47; https://doi.org/10.3390/thermo5040047 - 3 Nov 2025

Abstract

Coal-to-Synthetic Natural Gas (SNG) plays a crucial role in China’s decarbonization strategy but faces significant sustainability challenges due to its carbon-intensive nature. This study integrates Life Cycle Assessment (LCA) with Box–Behnken Design and Response Surface Methodology (BBD-RSM) to quantify and optimize key parameters [...] Read more.

Coal-to-Synthetic Natural Gas (SNG) plays a crucial role in China’s decarbonization strategy but faces significant sustainability challenges due to its carbon-intensive nature. This study integrates Life Cycle Assessment (LCA) with Box–Behnken Design and Response Surface Methodology (BBD-RSM) to quantify and optimize key parameters for emission reduction. The LCA results indicate that 90.48% of total emissions originate from the SNG production stage, while coal mining accounts for 9.38%, leading to a carbon intensity of 660.92 g CO₂^eq/kWh, second only to conventional coal power. Through BBD-RSM optimization, the optimal parameter combination was identified as a raw coal selection rate of 62.5%, an effective calorific value of 16.75 MJ/kg, and a conversion efficiency of 83%, corresponding to an energy-based rate of return (ERR) of 49.79%. The optimized scenario demonstrates a substantial reduction in total life-cycle emissions compared with the baseline, thereby improving the environmental viability of coal-to-SNG technology. Furthermore, this study employs the energy-based rate of return (ERR) as a normalization and comparative evaluation metric to quantitatively assess emission reduction potential. The ERR, combined with BBD-RSM, enables a more systematic exploration of emission-driving factors and enhances the application of statistical optimization methods in the coal-to-SNG sector. The findings provide practical strategies for promoting the low-carbon transformation of the coal-to-SNG industry and contribute to the broader advancement of sustainable energy development. Full article

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13 pages, 2945 KB

Open AccessFeature PaperArticle

Heat Treatment Effects on β Ti-10Mo-xMn Alloys for Biomedical Applications

by Mariana Luna Lourenço, Pedro Akira Bazaglia Kuroda and Carlos Roberto Grandini

Thermo 2025, 5(4), 46; https://doi.org/10.3390/thermo5040046 - 3 Nov 2025

Abstract

When it comes to developing new titanium alloys for biomaterials, β metastable alloys have been gaining the most attention from researchers, as they have a lower elastic modulus and the microstructure can be altered by adding other elements and heat treatments (HT), which [...] Read more.

When it comes to developing new titanium alloys for biomaterials, β metastable alloys have been gaining the most attention from researchers, as they have a lower elastic modulus and the microstructure can be altered by adding other elements and heat treatments (HT), which makes the material a promising biomaterial. The Ti-10Mo-Mn alloys were melted in an arc furnace. After ingot casting, a homogenization treatment (#T) was carried out, followed by the mechanical processing of hot rolling (#1) and subsequent annealing HT (#2). This work aimed to analyze the influence of some HT on the phase constituents, percentages, morphologies, distributions and selected mechanical properties, such as microhardness and elastic modulus in Ti-10Mo-xMn system alloys, ranging from 0 to 8% by weight. The results showed that alloys with low manganese content, classified as metastable, were sensitive to the HT in this study. From 4% manganese, the alloys had a stable β phase and were, therefore, not sensitive to the HT. The hardness of the alloys with 0 and 2% manganese remained high, possibly due to the presence of the omega phase. The elastic modulus increased from the hot rolling condition (#1) to annealing condition (#2) in all compositions. The Ti-10Mo-2Mn#1 alloy stood out among the alloys studied. It showed the lowest elastic modulus (~87 GPa), making it suitable for use as a biomaterial. Full article

(This article belongs to the Special Issue Thermal Science and Metallurgy)

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22 pages, 4002 KB

Open AccessArticle

A Laboratory Set-Up for Hands-On Learning of Heat Transfer Principles in Aerospace Engineering Education

by Pablo Salgado Sánchez, Antonio Rosado Lebrón, Andriy Borshchak Kachalov, Álvaro Oviedo, Jeff Porter and Ana Laverón Simavilla

Thermo 2025, 5(4), 45; https://doi.org/10.3390/thermo5040045 - 30 Oct 2025

Abstract

This paper describes a laboratory set-up designed to support hands-on learning of heat transfer principles in aerospace engineering education. Developed within the framework of experiential and project-based learning, the set-up enables students to experimentally characterize the convective coefficient of a cooling fan and [...] Read more.

This paper describes a laboratory set-up designed to support hands-on learning of heat transfer principles in aerospace engineering education. Developed within the framework of experiential and project-based learning, the set-up enables students to experimentally characterize the convective coefficient of a cooling fan and the thermo-optical properties of aluminum plates with different surface coatings, specifically their absorptivity and emissivity. A custom-built, LED-based radiation source (the ESAT Sun simulator) and a calibrated temperature acquisition system are used to emulate and monitor radiative heating under controlled conditions. Simplified physical models are developed for both the ESAT Sun simulator and the plates that capture the dominant thermal dynamics via first-order energy balances. The laboratory workflow includes real-time data acquisition, curve fitting, and thermal model inversion to estimate the convective and thermo-optical coefficients. The results demonstrate good agreement between the model predictions and observed temperatures, which supports the suitability of the set-up for education. The proposed activities can strengthen the student’s understanding of convective and radiative heat transport in aerospace applications while also fostering skills in data analysis, physical and numerical reasoning, and system-level thinking. Opportunities exist to expand the material library, refine the physical modeling, and evaluate the long-term pedagogical impact of the educational set-up described here. Full article

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18 pages, 3257 KB

Open AccessArticle

Influence of Motive Nozzle Supersonic Part Profiling on the Effectiveness of the Vaporization Process: Experimental Results

by Serhii Sharapov, Danylo Husiev, Anton Verbytskiy, Roman Vaskin, Ivan Kozii, Leonid Plyatsuk, Iryna Vaskina, Dmytro Hopkalo and Yuliia Denysenko

Thermo 2025, 5(4), 44; https://doi.org/10.3390/thermo5040044 - 23 Oct 2025

Abstract

This article presents experimental results for motive nozzles with profiled supersonic parts of parabolic, hyperbolic, and elliptical shapes, compared to conical nozzles with unprofiled supersonic parts. This study examined the effect of nozzle geometry and profile on thermodynamic and flow parameters of the [...] Read more.

This article presents experimental results for motive nozzles with profiled supersonic parts of parabolic, hyperbolic, and elliptical shapes, compared to conical nozzles with unprofiled supersonic parts. This study examined the effect of nozzle geometry and profile on thermodynamic and flow parameters of the vaporization process. The measured parameters included outlet pressure, flow velocity, and mass vapor content, along with dimensionless efficiency indicators, such as relative outflow velocity and the velocity coefficient. Graphical dependencies of these parameters on the relative initial underheating, (1 − ε_s0), were obtained. This parameter represents the ratio of the pressure difference between inlet and saturation conditions (at inlet temperature) to the inlet pressure. The results show that profiled nozzles operate effectively over a wider range of (1 − ε_s0) = 0.20–0.45, compared to conical unprofiled nozzles. The vaporization constant for profiled nozzles remained at b_n ≈ (2/3)^0.5 along their length. The velocity coefficients for profiled designs were 4–6% higher, and the volumetric vapor content at the outlet was also greater, indicating a more efficient vaporization process. Overall, the findings demonstrate that profiling the supersonic section of a motive nozzle improves the operating range, flow characteristics, and vaporization quality compared to conventional conical designs. Full article

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15 pages, 1243 KB

Open AccessArticle

Implementation of Carbon Utilization Technologies and Thermodynamic Organic Rankine Cycles in Biogas Combined Cycle Power Plants

by Gerardo G. Esquivel-Patiño, Fabricio Nápoles-Rivera and Arturo Jiménez-Gutiérrez

Thermo 2025, 5(4), 43; https://doi.org/10.3390/thermo5040043 - 22 Oct 2025

Abstract

Biogas has been identified as a sustainable resource of renewable and clean energy because of its social, economic, and environmental benefits. In this work, the analysis of a biogas combined cycle power plant coupled with a carbon capture and utilization (CCU) technology and [...] Read more.

Biogas has been identified as a sustainable resource of renewable and clean energy because of its social, economic, and environmental benefits. In this work, the analysis of a biogas combined cycle power plant coupled with a carbon capture and utilization (CCU) technology and an organic Rankine cycle (ORC) was considered. The integrated process was subjected to a multi-objective assessment considering energy, economic, environmental, and safety items. The CCU system was taken to produce syngas as a value-added product, and the use of different working fluids for the ORC, namely, R1234yf, R290, and R717, was also examined. Such working fluids were selected to represent options with varying environmental and inherent safety implications. It was shown that the integration of the CCU and ORC components to the biogas cycle plant can provide significant benefits that include a 48.65 kt/year syngas production, a decrease in carbon capture energy penalty by 33%, and a reduction in e-CO₂ emissions above 80% with respect to the stand-alone power plant. Comparison with conventional technologies also showed important environmental benefits. The analysis of inherent safety showed that the selection of working fluids for the ORC can have a significant impact on the process risk. From the set of working fluids considered in this work, R717 provided the best choice for the integrated system based on its lowest operational risk and the highest electricity production (355 kWe). The multi-objective approach used in this work allowed the quantification of benefits provided by the integration of CCUs and ORCs with respect to the base process within an overall economic, sustainability, and inherent safety assessment. Full article

(This article belongs to the Special Issue Thermodynamic Analysis and Modeling in Biomass Thermal Conversion Processes)

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