Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2026.104475
R. Pothi Raj, B. Raja
The experimental investigation on the interaction between the spray distribution and the heat and mass transfer parameters during spray drying of cathode electrode materials remain limited. This gap restricts the estimation of occurrence of regions of droplet evaporation and solid particle drying. An attempt is made to delineate these regions by mapping the temperature profiles obtained from 20 T-type thermocouples positioned at axial and radial positions within the spray drying chamber. The material Na2Fe0.6Mn0.4PO4F/C is utilized for the experiments. Using a volumetric approach, volumetric heat (hV) and mass transfer coefficient (kV), volumetric Nusselt number (NuV), and Sherwood number (ShV) are evaluated. The aforementioned parameters are evaluated for orifice diameter (d0) between 0.2 and 0.7 mm, feed solution injection pressure (PIN) between 2 bar and 7 bar, hot air inlet velocity (VIN) of 0.88 m/s and 1.18 m/s, and hot air inlet temperature (TIN) of 250 °C and 300 °C. The experimental results estimate that the spray penetration length (LP) is between 100 and 500 mm, with kV ranging from 3 to 27 s−1, NuV from 600 to 3700, ShV from 38 to 2300, and hV from 4.5 to 26 kWm−3K−1. The spray cone angle (θ) is determined by visualization techniques and it ranges from 45° to 80°. This work establishes design correlations between the spray distribution and heat and mass transfer parameters and future work will integrate moisture content and particle size distribution.
{"title":"Parametric investigation of spray drying Na2Fe0.6Mn0.4PO4F/C cathode material: evaluating heat and mass characteristics","authors":"R. Pothi Raj, B. Raja","doi":"10.1016/j.tsep.2026.104475","DOIUrl":"10.1016/j.tsep.2026.104475","url":null,"abstract":"<div><div>The experimental investigation on the interaction between the spray distribution and the heat and mass transfer parameters during spray drying of cathode electrode materials remain limited. This gap restricts the estimation of occurrence of regions of droplet evaporation and solid particle drying. An attempt is made to delineate these regions by mapping the temperature profiles obtained from 20 T-type thermocouples positioned at axial and radial positions within the spray drying chamber. The material Na<sub>2</sub>Fe<sub>0.6</sub>Mn<sub>0.4</sub>PO<sub>4</sub>F/C is utilized for the experiments. Using a volumetric approach, volumetric heat (<em>h<sub>V</sub></em>) and mass transfer coefficient (<em>k<sub>V</sub></em>), volumetric Nusselt number (<em>Nu<sub>V</sub></em>), and Sherwood number (<em>Sh<sub>V</sub></em>) are evaluated. The aforementioned parameters are evaluated for orifice diameter (<em>d<sub>0</sub></em>) between 0.2 and 0.7 mm, feed solution injection pressure (<em>P<sub>IN</sub></em>) between 2 bar and 7 bar, hot air inlet velocity (<em>V<sub>IN</sub></em>) of 0.88 m/s and 1.18 m/s, and hot air inlet temperature (<em>T<sub>IN</sub></em>) of 250 °C and 300 °C. The experimental results estimate that the spray penetration length (<em>L<sub>P</sub></em>) is between 100 and 500 mm, with <em>k<sub>V</sub></em> ranging from 3 to 27 s<sup>−1</sup>, <em>Nu<sub>V</sub></em> from 600 to 3700, <em>Sh<sub>V</sub></em> from 38 to 2300, and <em>h<sub>V</sub></em> from 4.5 to 26 kWm<sup>−3</sup>K<sup>−1</sup>. The spray cone angle (<em>θ</em>) is determined by visualization techniques and it ranges from 45° to 80°. This work establishes design correlations between the spray distribution and heat and mass transfer parameters and future work will integrate moisture content and particle size distribution.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104475"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2026.104484
Da-Hye Hwang , Yong-Seok Choi , Tae-Woo Lim
This study focuses on the thermal design of a reformer that produces hydrogen by extracting a portion of the boil-off gas generated from the fuel tank of an LNG-fueled ship. The reformer is a subsystem of a reformer-fuel cell system and is designed as a shell-and-tube heat exchanger, with a fixed lump of catalyst particles within the tubes and a bundle of these tubes installed within the shell. Designing the reformer requires determining the heat transfer coefficients and pressure drops inside and outside the tubes. For the thermal design of the particle bed in the tube, the heat transfer coefficient on the tube side is calculated using the correlation proposed by Wakao et al., which is widely used in the design of heat exchangers with spherical or cylindrical particle beds. The pressure drop across the particle bed packed in the tube is calculated using the correlation reported by Erdim et al. Based on the thermal design, the length of the reformer is predicted to be 1.72 m when the temperature difference between the shell-side outlet and tube-side inlet is approximately 70 ℃. This estimate aligns with the length (approximately 1.7 m) obtained from the demethanation reaction model of the reformer. The reforming process achieves a hydrogen yield of approximately 43 % with a methane conversion rate of approximately 98 %.
{"title":"Thermal design of the reformer in reformer-fuel cell systems for onboard hydrogen production in LNG-fueled ships","authors":"Da-Hye Hwang , Yong-Seok Choi , Tae-Woo Lim","doi":"10.1016/j.tsep.2026.104484","DOIUrl":"10.1016/j.tsep.2026.104484","url":null,"abstract":"<div><div>This study focuses on the thermal design of a reformer that produces hydrogen by extracting a portion of the boil-off gas generated from the fuel tank of an LNG-fueled ship. The reformer is a subsystem of a reformer-fuel cell system and is designed as a shell-and-tube heat exchanger, with a fixed lump of catalyst particles within the tubes and a bundle of these tubes installed within the shell. Designing the reformer requires determining the heat transfer coefficients and pressure drops inside and outside the tubes. For the thermal design of the particle bed in the tube, the heat transfer coefficient on the tube side is calculated using the correlation proposed by Wakao et al., which is widely used in the design of heat exchangers with spherical or cylindrical particle beds. The pressure drop across the particle bed packed in the tube is calculated using the correlation reported by Erdim et al. Based on the thermal design, the length of the reformer is predicted to be 1.72 m when the temperature difference between the shell-side outlet and tube-side inlet is approximately 70 ℃. This estimate aligns with the length (approximately 1.7 m) obtained from the demethanation reaction model of the reformer. The reforming process achieves a hydrogen yield of approximately 43 % with a methane conversion rate of approximately 98 %.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104484"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2025.104452
Xiang Fang , Yong Yang , Yajun Huang , Xiaochun Zhang , Fei Ren , Xin Li
This article uses a small-scale surface fire experimental platform to study the thermal radiation and temperature distribution in the boundary areas of forest towns of surface fires. Pine needle material was used as fuel and laid on a fuel bed with a length of 6.0 m and a width of 0.6 m, where laying width and thickness (load) of pine needle material could vary. Results show that: (1) The fire spread rate increases with the increase of fuel laying width and thickness. This is because an increase in fuel laying width and thickness could cause an increase in flame size (width, length), which in turn increases the thermal radiation on unburned fuel in front of the flame, accelerating the fire spread. A non-dimensional correlation was carried out for the fire spread rate of different laying widths and thicknesses, and a fire spread rate model was established based on heat transfer. (2) The radiation heat flux increases with the increase of fuel laying width, and the increase of fuel laying thickness. The closer the height is to the midpoint of flame height, the greater the radiation heat flux. A radiation heat flux model was established based on solid-state flame model. (3) The temperature in the vertical direction of boundary area increases with the increase of fuel laying width, and decreases with the increase of vertical height, and slightly increases with the increase of fuel laying load. A temperature profile model was established based on the analysis of fire heat transfer.
{"title":"Experimental study on fire spread rate, thermal radiation and temperature profile at Wildland-Urban Interface of pine needle material surface fires","authors":"Xiang Fang , Yong Yang , Yajun Huang , Xiaochun Zhang , Fei Ren , Xin Li","doi":"10.1016/j.tsep.2025.104452","DOIUrl":"10.1016/j.tsep.2025.104452","url":null,"abstract":"<div><div>This article uses a small-scale surface fire experimental platform to study the thermal radiation and temperature distribution in the boundary areas of forest towns of surface fires. Pine needle material was used as fuel and laid on a fuel bed with a length of 6.0 m and a width of 0.6 m, where laying width and thickness (load) of pine needle material could vary. Results show that: (1) The fire spread rate increases with the increase of fuel laying width and thickness. This is because an increase in fuel laying width and thickness could cause an increase in flame size (width, length), which in turn increases the thermal radiation on unburned fuel in front of the flame, accelerating the fire spread. A non-dimensional correlation was carried out for the fire spread rate of different laying widths and thicknesses, and a fire spread rate model was established based on heat transfer. (2) The radiation heat flux increases with the increase of fuel laying width, and the increase of fuel laying thickness. The closer the height is to the midpoint of flame height, the greater the radiation heat flux. A radiation heat flux model was established based on solid-state flame model. (3) The temperature in the vertical direction of boundary area increases with the increase of fuel laying width, and decreases with the increase of vertical height, and slightly increases with the increase of fuel laying load. A temperature profile model was established based on the analysis of fire heat transfer.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104452"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Incorporating Phase Change Material (PCM) into food packaging can highly improve its performance of maintaining product temperature during temperature breaks. One of the primary challenges in using PCM is the risk of leakage, a problem that can be mitigated by encapsulation. An experimental set-up was developed to study the thermal behaviour of a PCM (tetradecane) encapsulated in bio-sourced starch films using sustainable chitin particles for Pickering-type stabilisation, and to compare it with the bulk configuration. The experimental results permit the validation of a thermal model for bulk PCM and microencapsulated PCM. The model was used to simulate variations in phase-change temperature. It was found that the optimal melting temperature range depends on both the ambient temperature and the threshold. The optimal melting temperature range is between 0 and 6 °C for a 4 °C threshold. The use of an air gap inside the food packaging improves the performance only slightly. Increasing the number of films enhances the stored energy while using PCMs at different phase change temperatures can offer high potential for maintaining product temperature. Unlike previous studies, this work proposed biobased stabilization solutions and combined experimental and modelling approaches to address various PCM configurations for food packaging design optimization.
{"title":"Optimizing the design of food packaging containing phase-change material using experimental and numerical approaches","authors":"Hong-Minh Hoang , Anthony Delahaye , Joelle Rassy , Jean Eudes Maigret , Denis Lourdin , Somia Haouache , Isabelle Capron , Laurence Fournaison","doi":"10.1016/j.tsep.2025.104453","DOIUrl":"10.1016/j.tsep.2025.104453","url":null,"abstract":"<div><div>Incorporating Phase Change Material (PCM) into food packaging can highly improve its performance of maintaining product temperature during temperature breaks. One of the primary challenges in using PCM is the risk of leakage, a problem that can be mitigated by encapsulation. An experimental set-up was developed to study the thermal behaviour of a PCM (tetradecane) encapsulated in bio-sourced starch films using sustainable chitin particles for Pickering-type stabilisation, and to compare it with the bulk configuration. The experimental results permit the validation of a thermal model for bulk PCM and microencapsulated PCM. The model was used to simulate variations in phase-change temperature. It was found that the optimal melting temperature range depends on both the ambient temperature and the threshold. The optimal melting temperature range is between 0 and 6 °C for a 4 °C threshold. The use of an air gap inside the food packaging improves the performance only slightly. Increasing the number of films enhances the stored energy while using PCMs at different phase change temperatures can offer high potential for maintaining product temperature. Unlike previous studies, this work proposed biobased stabilization solutions and combined experimental and modelling approaches to address various PCM configurations for food packaging design optimization.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104453"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2026.104483
Jin Sub Kim , Wookyoung Kim , Hak Soo Kim , Young Kim
The heat transfer performance of a falling film evaporator using ammonia was thoroughly investigated by directly comparing it with submerged natural convection/pool boiling, focusing on the effect of tube position in a vertical tube arrangement. Falling film evaporation of ammonia in a vertical tube array was examined at saturation temperatures ranging from 10 to 30 ℃, comparing it with submerged natural convection/pool boiling under low heat flux conditions (0.5–18.2 kW/m2). Five stainless steel test tubes having an outer diameter of 15.87 mm were arranged vertically, with one submerged in liquid ammonia and the others exposed to falling film evaporation. Experimental results show that heat transfer coefficients (HTCs) in the falling film evaporation are up to 4.4 times higher than those in the submerged natural convection/pool boiling. The uppermost tube exhibited the lowest HTC among the film-evaporated tubes due to the formation of locally thick liquid films. Empirical correlations were developed to predict the HTC as a function of Reynolds number, Prandtl number, reduced pressure, and dimensionless heat flux, with a mean absolute percentage error of less than 11.1 %. The proposed correlations are applicable to the tested range of 10–30 °C and low heat flux (0.5–18.2 kW/m2). Enhanced low-fin tubes exhibited 10–30 % improved thermal performance over smooth tubes, particularly at higher saturation temperatures, though the performance gain was limited at low temperatures due to hindered liquid spreading by the fin structures. The findings highlight the critical role of tube arrangement, film flow characteristics, and enhanced surfaces in optimizing ammonia falling film evaporators for efficient and environmentally friendly heat pump applications.
{"title":"Falling film evaporation of ammonia on smooth and Low-Fin tube arrays","authors":"Jin Sub Kim , Wookyoung Kim , Hak Soo Kim , Young Kim","doi":"10.1016/j.tsep.2026.104483","DOIUrl":"10.1016/j.tsep.2026.104483","url":null,"abstract":"<div><div>The heat transfer performance of a falling film evaporator using ammonia was thoroughly investigated by directly comparing it with submerged natural convection/pool boiling, focusing on the effect of tube position in a vertical tube arrangement. Falling film evaporation of ammonia in a vertical tube array was examined at saturation temperatures ranging from 10 to 30 ℃, comparing it with submerged natural convection/pool boiling under low heat flux conditions (0.5–18.2 kW/m<sup>2</sup>). Five stainless steel test tubes having an outer diameter of 15.87 mm were arranged vertically, with one submerged in liquid ammonia and the others exposed to falling film evaporation. Experimental results show that heat transfer coefficients (HTCs) in the falling film evaporation are up to 4.4 times higher than those in the submerged natural convection/pool boiling. The uppermost tube exhibited the lowest HTC among the film-evaporated tubes due to the formation of locally thick liquid films. Empirical correlations were developed to predict the HTC as a function of Reynolds number, Prandtl number, reduced pressure, and dimensionless heat flux, with a mean absolute percentage error of less than 11.1 %. The proposed correlations are applicable to the tested range of 10–30 °C and low heat flux (0.5–18.2 kW/m<sup>2</sup>). Enhanced low-fin tubes exhibited 10–30 % improved thermal performance over smooth tubes, particularly at higher saturation temperatures, though the performance gain was limited at low temperatures due to hindered liquid spreading by the fin structures. The findings highlight the critical role of tube arrangement, film flow characteristics, and enhanced surfaces in optimizing ammonia falling film evaporators for efficient and environmentally friendly heat pump applications.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104483"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2026.104481
Talha Bin Nadeem , Muhammad Imran , Adeel Arshad , Emad Tandis
This study presents a comprehensive computational analysis, parametric study and optimization of a finned-tube heat exchanger (FTHE) integrating with Multi-Directional Wind Tower (MDWT) in Indirect Evaporative Cooling (IEC) applications aimed at improving thermal performance while minimizing pressure drop (). A parametric investigation was conducted using validated computational fluid dynamics (CFD) simulations to assess the effects of fin height (), fin thickness (), and fin spacing () on thermal performance and flow resistance. Key trends revealed that influences the heat transfer coefficient () non-linearly, while shows diminishing returns beyond a critical value. had a minor effect on but improved fin efficiency (), especially at higher Reynolds numbers (). A performance indicator was defined as the ratio of Nusselt number and Euler number to simultaneously enhance heat transfer and reduce flow resistance. A MATLAB-based optimization algorithm was then implemented to determine the configuration exhibiting the highest performance score. The optimal design was found to have a of 4 mm, of 1 mm, and of 2 mm, achieving a of 195.57, of 4.48, and of 43.61. The optimized geometry design observed 88.32 % increment in in comparison to the base case for model validation. Correlation models are developed for and using log–log linearization technique and achieved high accuracy of R2 of 92.47 % and 96.58 %, respectively. It offers reliable predictions for future design efforts. The findings provide practical insights into integrating FTHE in IEC with balanced thermal and hydraulic performance.
{"title":"Parametric study and design optimization of finned tube heat exchangers for enhanced indirect evaporative cooling","authors":"Talha Bin Nadeem , Muhammad Imran , Adeel Arshad , Emad Tandis","doi":"10.1016/j.tsep.2026.104481","DOIUrl":"10.1016/j.tsep.2026.104481","url":null,"abstract":"<div><div>This study presents a comprehensive computational analysis, parametric study and optimization of a finned-tube heat exchanger (FTHE) integrating with Multi-Directional Wind Tower (MDWT) in Indirect Evaporative Cooling (IEC) applications aimed at improving thermal performance while minimizing pressure drop (<span><math><mrow><mi>Δ</mi><mi>p</mi></mrow></math></span>). A parametric investigation was conducted using validated computational fluid dynamics (CFD) simulations to assess the effects of fin height (<span><math><msub><mi>h</mi><mi>f</mi></msub></math></span>), fin thickness (<span><math><msub><mi>t</mi><mi>f</mi></msub></math></span>), and fin spacing (<span><math><msub><mi>S</mi><mi>f</mi></msub></math></span>) on thermal performance and flow resistance. Key trends revealed that <span><math><msub><mi>S</mi><mi>f</mi></msub></math></span> influences the heat transfer coefficient (<span><math><mi>h</mi></math></span>) non-linearly, while <span><math><msub><mi>h</mi><mi>f</mi></msub></math></span> shows diminishing returns beyond a critical value. <span><math><msub><mi>t</mi><mi>f</mi></msub></math></span> had a minor effect on <span><math><mrow><mi>Δ</mi><mi>p</mi></mrow></math></span> but improved fin efficiency (<span><math><msub><mi>η</mi><mi>f</mi></msub></math></span>), especially at higher Reynolds numbers (<span><math><mrow><mi>Re</mi></mrow></math></span>). A performance indicator was defined as the ratio of Nusselt number <span><math><mfenced><mrow><mi>N</mi><mi>u</mi></mrow></mfenced></math></span> and Euler number <span><math><mrow><mo>(</mo><mi>E</mi><mi>u</mi><mo>)</mo></mrow></math></span> to simultaneously enhance heat transfer and reduce flow resistance. A MATLAB-based optimization algorithm was then implemented to determine the configuration exhibiting the highest performance score. The optimal design was found to have a <span><math><msub><mi>h</mi><mi>f</mi></msub></math></span> of 4 mm, <span><math><msub><mi>t</mi><mi>f</mi></msub></math></span> of 1 mm, and <span><math><msub><mi>S</mi><mi>f</mi></msub></math></span> of 2 mm, achieving a <span><math><mrow><mi>Nu</mi></mrow></math></span> of 195.57, <span><math><mrow><mi>Eu</mi></mrow></math></span> of 4.48, and <span><math><mrow><mi>Nu</mi><mo>/</mo><mi>E</mi><mi>u</mi></mrow></math></span> of 43.61. The optimized geometry design observed 88.32 % increment in <span><math><mrow><mi>Nu</mi></mrow></math></span> in comparison to the base case for model validation. Correlation models are developed for <span><math><mrow><mi>Nu</mi></mrow></math></span> and <span><math><mrow><mi>Eu</mi></mrow></math></span> using log–log linearization technique and achieved high accuracy of R<sup>2</sup> of 92.47 % and 96.58 %, respectively. It offers reliable predictions for future design efforts. The findings provide practical insights into integrating FTHE in IEC with balanced thermal and hydraulic performance.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104481"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2025.104472
Mete Öğüç
<div><div>The thermal conductivity of sand strongly depends on its moisture content, with wet or partially saturated sands typically exhibiting values above <span><math><mrow><mn>1</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. Reliable estimates are important in geotechnical, civil, and energy engineering applications where sands act as natural or engineered heat-transfer media. In this work, laboratory experiments and finite element method (FEM) were combined to evaluate the effective conductivity of moist sand. Two buried-source configurations were tested: a U-shaped aluminum tube circulating hot water and a vertically embedded solid aluminum cylinder with internal resistance heating. The effective conductivity was back-calculated using classical conduction shape factors from the measured heat rates and temperature differences, and the same setups were reproduced numerically in two-dimensional steady-state finite element models. The U-tube analysis yielded values of 0.99–<span><math><mrow><mn>1</mn><mo>.</mo><mn>09</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, while the cylinder experiment gave 1.34–<span><math><mrow><mn>1</mn><mo>.</mo><mn>62</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> depending on the assumed air-side heat transfer coefficient. Finite element predictions from two-dimensional steady-state surrogate models were consistent with the measured temperature levels at the monitored locations for <span><math><mrow><mi>k</mi><mo>=</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></math></span>–<span><math><mrow><mn>1</mn><mo>.</mo><mn>1</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, providing an internal cross-check of the inferred conductivity range. Together, the results indicate an effective conductivity of 1.0–<span><math><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, broadly consistent with literature values and with the measured moisture contents. The study demonstrates that simple benchtop experiments, combined with shape-factor analysis and FEM, can provide practical conductivity estimates for porous media and serve as an instructive framework for conduction problems involving buried heat sources.</div></di
{"title":"Experimental determination and finite element modeling of thermal conductivity in moist sand","authors":"Mete Öğüç","doi":"10.1016/j.tsep.2025.104472","DOIUrl":"10.1016/j.tsep.2025.104472","url":null,"abstract":"<div><div>The thermal conductivity of sand strongly depends on its moisture content, with wet or partially saturated sands typically exhibiting values above <span><math><mrow><mn>1</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. Reliable estimates are important in geotechnical, civil, and energy engineering applications where sands act as natural or engineered heat-transfer media. In this work, laboratory experiments and finite element method (FEM) were combined to evaluate the effective conductivity of moist sand. Two buried-source configurations were tested: a U-shaped aluminum tube circulating hot water and a vertically embedded solid aluminum cylinder with internal resistance heating. The effective conductivity was back-calculated using classical conduction shape factors from the measured heat rates and temperature differences, and the same setups were reproduced numerically in two-dimensional steady-state finite element models. The U-tube analysis yielded values of 0.99–<span><math><mrow><mn>1</mn><mo>.</mo><mn>09</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, while the cylinder experiment gave 1.34–<span><math><mrow><mn>1</mn><mo>.</mo><mn>62</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> depending on the assumed air-side heat transfer coefficient. Finite element predictions from two-dimensional steady-state surrogate models were consistent with the measured temperature levels at the monitored locations for <span><math><mrow><mi>k</mi><mo>=</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></math></span>–<span><math><mrow><mn>1</mn><mo>.</mo><mn>1</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, providing an internal cross-check of the inferred conductivity range. Together, the results indicate an effective conductivity of 1.0–<span><math><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>W</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, broadly consistent with literature values and with the measured moisture contents. The study demonstrates that simple benchtop experiments, combined with shape-factor analysis and FEM, can provide practical conductivity estimates for porous media and serve as an instructive framework for conduction problems involving buried heat sources.</div></di","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104472"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2026.104477
Xu-Ge Wang , Li Zhang , You-Rong Li
Droplet evaporation is a common physical phenomenon in daily life and industrial production. It is of great significance to understand its evaporation characteristics. This study employs the finite element method coupled with moving mesh technology to investigate the influence of gravity on the evaporation dynamics of ethanol–water binary mixture droplets (BMD) under different substrate temperatures and initial ethanol mass fractions. The results indicate that the evaporation rate of BMD is the slowest under zero-gravity condition and the fastest for the sessile droplet. The zero-gravity BMD exhibits a 27.6 % longer lifespan compared with the sessile BMD. As the substrate temperature increases, the lifespan difference between sessile and pendant BMDs becomes more pronounced. With the increasing initial ethanol mass fraction, the volume difference between sessile and pendant droplets decreases in the later stages. This research promotes a deeper understanding of the mass and heat transfer mechanisms in the evaporation process of BMD.
{"title":"Numerical simulation on the influence of gravity on binary droplet evaporation under different conditions","authors":"Xu-Ge Wang , Li Zhang , You-Rong Li","doi":"10.1016/j.tsep.2026.104477","DOIUrl":"10.1016/j.tsep.2026.104477","url":null,"abstract":"<div><div>Droplet evaporation is a common physical phenomenon in daily life and industrial production. It is of great significance to understand its evaporation characteristics. This study employs the finite element method coupled with moving mesh technology to investigate the influence of gravity on the evaporation dynamics of ethanol–water binary mixture droplets (BMD) under different substrate temperatures and initial ethanol mass fractions. The results indicate that the evaporation rate of BMD is the slowest under zero-gravity condition and the fastest for the sessile droplet. The zero-gravity BMD exhibits a 27.6 % longer lifespan compared with the sessile BMD. As the substrate temperature increases, the lifespan difference between sessile and pendant BMDs becomes more pronounced. With the increasing initial ethanol mass fraction, the volume difference between sessile and pendant droplets decreases in the later stages. This research promotes a deeper understanding of the mass and heat transfer mechanisms in the evaporation process of BMD.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104477"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.tsep.2025.104471
Roman M. Fedorenko , Dmitrii V. Antonov , Pavel A. Strizhak , Oyuna Rybdylova , Sergei S. Sazhin
The results of incorporating two recently developed models of composite droplet puffing/micro-explosion in a customised version of ANSYS Fluent via UDFs (User-Defined Functions) are presented. Both models, assuming that a water subdroplet is located in the centre of a stationary spherical fuel droplet, apply analytical solutions to the temperature equation within the droplet. The first model, known as the analytical model, leads to the analytical expression for the distribution of temperature in the droplet, which is valid at all times until the onset of puffing/micro-explosion. The second model, known as the analytical–numerical model, leads to a similar expression, but this expression is valid only during a short timestep. It is implemented within a numerical code where the prediction of the model at the end of a timestep is used as the initial condition for the next timestep with updated values of thermophysical parameters. The customised ANSYS Fluent version with the new analytical–numerical model is verified by comparing its results with the predictions of the in-house code. The predictions of the latter code were earlier verified by comparing the predictions of the analytical–numerical model and those of the purely numerical model. Reasonably good agreement between predicted and observed (both in-house and published) times to puffing/micro-explosion is demonstrated, especially at small initial droplet radii and high temperatures.
{"title":"Application of ANSYS Fluent to the analysis of puffing/micro-explosion of composite droplets","authors":"Roman M. Fedorenko , Dmitrii V. Antonov , Pavel A. Strizhak , Oyuna Rybdylova , Sergei S. Sazhin","doi":"10.1016/j.tsep.2025.104471","DOIUrl":"10.1016/j.tsep.2025.104471","url":null,"abstract":"<div><div>The results of incorporating two recently developed models of composite droplet puffing/micro-explosion in a customised version of ANSYS Fluent via UDFs (User-Defined Functions) are presented. Both models, assuming that a water subdroplet is located in the centre of a stationary spherical fuel droplet, apply analytical solutions to the temperature equation within the droplet. The first model, known as the analytical model, leads to the analytical expression for the distribution of temperature in the droplet, which is valid at all times until the onset of puffing/micro-explosion. The second model, known as the analytical–numerical model, leads to a similar expression, but this expression is valid only during a short timestep. It is implemented within a numerical code where the prediction of the model at the end of a timestep is used as the initial condition for the next timestep with updated values of thermophysical parameters. The customised ANSYS Fluent version with the new analytical–numerical model is verified by comparing its results with the predictions of the in-house code. The predictions of the latter code were earlier verified by comparing the predictions of the analytical–numerical model and those of the purely numerical model. Reasonably good agreement between predicted and observed (both in-house and published) times to puffing/micro-explosion is demonstrated, especially at small initial droplet radii and high temperatures.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104471"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rapid industrialization and population growth in developing countries have increased energy demand, emphasizing the need for sustainable alternatives. Growing environmental concerns have increased interest in thermal conversion methods such as pyrolysis, co-pyrolysis, and biomass gasification for converting agricultural and municipal wastes into clean energy. This investigation examines the impact of the Equivalence Ratio (ER) on Carbon Conversion Efficiency (CCE) and resultant syngas composition across various feedstocks within a Bubbling Fluidized Bed Gasification (BFBG) system. Computational Fluid Dynamics (CFD) simulations were performed to analyse gas–solid hydrodynamics. CFD analysis indicated that lighter feedstocks, such as rice husk, migrated to the freeboard region at 0.4ER, whereas denser materials, including groundnut shell and wooden shavings, remained concentrated in the mid-bed zone, resulting in enhanced gasification reactions. Experimental results revealed that increasing the ER enhanced hydrogen and methane concentrations across all feedstocks. Groundnut shell achieved 6.4 % H2, 5.6 % CH4, a gross calorific value (GCV) of 4.6 MJ.m−3, and a CCE of 83 % at 0.4ER. In contrast, rice husk showed minimal improvement with 3.6 % H2 due to its high ash content and exhibited the lowest CCE of 35 %. Wood shavings displayed moderate gasification performance with 4.4 % H2 and 4.2 % CH4. The surgical face mask demonstrated superior performance, producing 17.6 % H2 and 9.4 % CH4 at 0.4ER, with a high-calorific syngas (8 MJ·m−3GCV), confirming its efficiency as a waste-to-energy feedstock. The correlation between CFD predictions and experimental data validated the reliability of the model and its applicability for optimizing feedstock utilization in sustainable thermal energy generation.
{"title":"Waste to energy: performance evaluation of a bubbling fluidized bed gasifier using biomass blends and facemask","authors":"Dharmendra D. Sapariya , Umang Patdiwala , Jay Makwana , Avithi Desappan Dhass , Jignesh Makwana , Dhiren Patel , Ruchir Parikh , Mustufa Haider Abidi , Khalid Saeed , Hisham Alkhalefah","doi":"10.1016/j.tsep.2025.104470","DOIUrl":"10.1016/j.tsep.2025.104470","url":null,"abstract":"<div><div>Rapid industrialization and population growth in developing countries have increased energy demand, emphasizing the need for sustainable alternatives. Growing environmental concerns have increased interest in thermal conversion methods such as pyrolysis, co-pyrolysis, and biomass gasification for converting agricultural and municipal wastes into clean energy. This investigation examines the impact of the Equivalence Ratio (ER) on Carbon Conversion Efficiency (CCE) and resultant syngas composition across various feedstocks within a Bubbling Fluidized Bed Gasification (BFBG) system. Computational Fluid Dynamics (CFD) simulations were performed to analyse gas–solid hydrodynamics. CFD analysis indicated that lighter feedstocks, such as rice husk, migrated to the freeboard region at 0.4ER, whereas denser materials, including groundnut shell and wooden shavings, remained concentrated in the mid-bed zone, resulting in enhanced gasification reactions. Experimental results revealed that increasing the ER enhanced hydrogen and methane concentrations across all feedstocks. Groundnut shell achieved 6.4 % H<sub>2</sub>, 5.6 % CH<sub>4</sub>, a gross calorific value (GCV) of 4.6 MJ.m<sup>−3</sup>, and a CCE of 83 % at 0.4ER. In contrast, rice husk showed minimal improvement with 3.6 % H<sub>2</sub> due to its high ash content and exhibited the lowest CCE of 35 %. Wood shavings displayed moderate gasification performance with 4.4 % H<sub>2</sub> and 4.2 % CH<sub>4</sub>. The surgical face mask demonstrated superior performance, producing 17.6 % H<sub>2</sub> and 9.4 % CH<sub>4</sub> at 0.4ER, with a high-calorific syngas (8 MJ·m<sup>−3</sup>GCV), confirming its efficiency as a waste-to-energy feedstock. The correlation between CFD predictions and experimental data validated the reliability of the model and its applicability for optimizing feedstock utilization in sustainable thermal energy generation.</div></div>","PeriodicalId":23062,"journal":{"name":"Thermal Science and Engineering Progress","volume":"69 ","pages":"Article 104470"},"PeriodicalIF":5.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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