{"title":"Exploration of PCM melting in a heated enclosure with vertical plate fins: Experimental analysis","authors":"A. Ali Rabienataj Darzi , S. Morteza Mousavi","doi":"10.1016/j.ijthermalsci.2025.109884","DOIUrl":"10.1016/j.ijthermalsci.2025.109884","url":null,"abstract":"<div><div>This study investigates the enhancement of thermal performance in phase change materials (PCMs) through the application of fins. PCMs are renowned for their ability to store energy with minimal temperature fluctuations, rendering them valuable in thermal energy storage systems. However, their low thermal conductivity constrains heat transfer efficiency. By increasing the surface area, fins can enhance convective heat transfer and offer a solution to this limitation. The research conducts experimental analyses on the efficacy of vertical fins within an enclosure heated by a single vertical wall, emphasizing their influence on PCM thermal performance. Melt fronts are monitored at various time intervals, and local temperatures are recorded at nine specific points. The study explores three types of fins: non-perforated fins, circular-perforated fins, and fins with oval cuts. The findings demonstrate a significant improvement in PCM heat transfer rates and thermal behavior with the incorporation of fins, effectively lowering temperatures in proximity to the heat source. Specifically, the inclusion of 1, 3, and 5 non-perforated fins results in reductions of PCM melting times by 13 %, 32 %, and 39 %, respectively. The maximum melting rates for the cases with 5, 3, and 1 non-perforated fins are approximately 133 %, 90 %, and 22 % higher, respectively, compared to the case without fins. Furthermore, the research identifies an efficient fin design with oval cuts, achieving the shortest melting time while remaining cost-effective and lightweight. This indicates that the melting rate in the final stage of the melting process for this design is higher than in the other cases. This design features 30 % less surface area and 40 % less weight than complete fins, making it an attractive option for thermal systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109884"},"PeriodicalIF":4.9,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143685493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Modelling the solidification process of supercooled phase change materials with high Prandtl number using the total enthalpy-based lattice Boltzmann method","authors":"Baoxin Cao, Guobing Zhou","doi":"10.1016/j.ijthermalsci.2025.109881","DOIUrl":"10.1016/j.ijthermalsci.2025.109881","url":null,"abstract":"<div><div>Modelling the supercooled solidification of PCMs is challenging due to the multi-value problem particularly for high Prandtl numbers (<em>Pr</em>). An improved total enthalpy-based lattice Boltzmann method is applied to simulate the solidification process of supercooled sodium acetate trihydrate (SAT, <em>Pr</em> = 40) in a vertical cylindrical container triggered by local cooling. The evolutions of the SAT temperature profile, solid fraction and particularly the solidification front are monitored, and the effects of the cold source temperature (<em>T</em><sub>cool</sub>) and the cooling area (<em>l</em> × <em>l</em>) are analyzed. The results show that the presented method accurately characterizes the supercooled solidification; decreasing <em>T</em><sub>cool</sub> from −5.5 °C to −7 °C reduces the induction time by 95.7 % and the discharging period by 11.1 %; increasing cooling area <em>l</em> × <em>l</em> from 2 × 2 cm<sup>2</sup> to 8 × 8 cm<sup>2</sup> also shortens the induction time from 11 s to 7 s and the discharging period by up to 500 s. The larger cooling area <em>l</em> × <em>l</em> accelerates the movement of the solidification front and also has a significant impact on its morphology. The present model proposes an alternative numerical method for predicting the discharging performance of the supercooled high-<em>Pr</em> PCMs inside containers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109881"},"PeriodicalIF":4.9,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143685492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Thermo-hydraulic performance enhancement in novel secondary connected fractal heat sink with cavities","authors":"Shashank Singh, Anup Malik, Harlal Singh Mali","doi":"10.1016/j.ijthermalsci.2025.109855","DOIUrl":"10.1016/j.ijthermalsci.2025.109855","url":null,"abstract":"<div><div>The flexible geometries of microchannel heat sinks (MCHS) allow for modified cooling solutions for a wide range of applications. This adaptability enables heat dissipation enhancement in a variety of sectors, including renewable energy systems and microelectronics. This study aims to build novel MCHS device for thermo-hydraulic performance enhancement. Two devices are, bottom cavities secondary connected fractal heat sink with one branching level (BCSC-FHS-L1) and two branching level (BCSC-FHS-L2), 3D printed by laser powder bed fusion (LPBF) technique. AlSi10Mg alloy is used as solid substrate and water as fluid with single-phase flow. Their performances are studied numerically and validated experimentally using an in-house developed test setup. BCSC-FHS-L2 shows superior thermal performance with the maximum enhancement of 35% in average Nusselt number (<span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi></mrow><mrow><mi>a</mi><mi>v</mi><mi>g</mi></mrow></msub></mrow></math></span>) at Reynolds number (<span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>)=793 with 67% increment in pressure drop (<span><math><mrow><mi>Δ</mi><mi>P</mi></mrow></math></span>). BCSC-FHS-L2 shows the maximum overall performance (<span><math><mrow><mi>O</mi><mi>P</mi></mrow></math></span>) at <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>=270 with 17% enhancement compared to BCSC-FHS-L1 device.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109855"},"PeriodicalIF":4.9,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A.S.M. Rokonuzzaman , Kasim Erdem , Bayram Şahin , Mehmed Rafet Özdemir
{"title":"Experimental study of a single-phase immersion cooling system with natural and forced convection","authors":"A.S.M. Rokonuzzaman , Kasim Erdem , Bayram Şahin , Mehmed Rafet Özdemir","doi":"10.1016/j.ijthermalsci.2025.109868","DOIUrl":"10.1016/j.ijthermalsci.2025.109868","url":null,"abstract":"<div><div>The rapid advancement of the electronics industry has led to the emergence of miniaturized, high-speed devices with significant amount of volumetric heat generation. Immersion cooling systems offer an effective solution for managing high heat loads, particularly in data centers and battery thermal management systems. However, several fundamental issues of the underlying physical phenomena still need to be addressed to improve the efficiency of these systems. In this study, an immersion cooling system using Novec 7100 dielectric liquid has been experimentally investigated having four electric cartridge heaters with circular and square cross-sections. The effect of distance between heaters on the surface temperature was analyzed under different flow conditions. Furthermore, the effect of heater cross-section on the heat transfer coefficient was examined. For natural convection, the heat transfer coefficient increased as the distance between the heaters was increased for both heaters. As expected, the forced convection mechanism was found to be significantly more effective in heat removal compared to natural convection. At high heat flux values, the heat transfer coefficient was found to be higher for square heaters due to their 1.15 times larger surface area. However, for low heat flux values, the heat transfer coefficient was higher for circular heaters than the square heaters. These findings provide valuable insights into the optimization of immersion cooling systems, highlighting the influence of heater geometry and heater spacing on thermal management efficiency.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109868"},"PeriodicalIF":4.9,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143685491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Hot surface ignition delay time of ammonia-hydrogen-methane mixtures","authors":"Amir Hossein Sharifi Ilkhchi, Amir Mahdi Tahsini","doi":"10.1016/j.ijthermalsci.2025.109885","DOIUrl":"10.1016/j.ijthermalsci.2025.109885","url":null,"abstract":"<div><div>In this research, the effects of adding hydrogen and ammonia to the stoichiometric methane-air mixture, as well as adding ammonia to the stoichiometric hydrogen-air mixture, on ignition delay time changes near a hot surface at two constant temperatures (1400 K and 1600 K) are numerically investigated using a detailed mechanism. The hydrogen-to-methane effectiveness limit (HMEL) is defined in this paper, indicating the point at which the beneficial effect of hydrogen on reducing ignition delay time is reversed, resulting in longer ignition delay times compared to the original mixture, stoichiometric methane-air. Additionally, the hydrogen-to-methane optimal range (HMOR) represents the optimal hydrogen addition range to the stoichiometric methane-air mixture that achieves the lowest ignition delay times. An unpredictable jump in ignition delay time is observed in the methane-hydrogen-air mixture at a hot surface temperature of 1600 K when approximately 14.5 % hydrogen is added. Additionally, adding more than 16 % hydrogen results in longer ignition delay times at higher hot surface temperatures. Conversely, the ignition delay time increases with addition of ammonia in both methane and hydrogen mixtures. Furthermore, it is concluded that adding more than 23–25 % ammonia to the stoichiometric hydrogen-air mixture renders it non-ignitable by a hot surface at 1600 K. This study highlights the impact of hydrogen and ammonia addition on ignition delay time, offering valuable insights for practical applications and providing a foundation for further research on the combustion characteristics of fuels, particularly ammonia and hydrogen.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109885"},"PeriodicalIF":4.9,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143645124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Balance regulation of heat transfer and flow performances of convective heat exchange of microchannel array structures","authors":"Chaomeng Chen, Jie Wang, Liyang Wang, Ping Zhang","doi":"10.1016/j.ijthermalsci.2025.109882","DOIUrl":"10.1016/j.ijthermalsci.2025.109882","url":null,"abstract":"<div><div>As chip integration density increases, the demand for efficient thermal management becomes critical. Traditional microchannel structures often face a trade-off between heat transfer enhancement and increased flow resistance. To address this issue, this study proposes a novel reverse optimization strategy for microchannel array structures, inspired by the natural configurations of leaf veins and spider webs. The optimization process involves two key stages: first, minimizing the maximum thermal resistance of individual microchannel units; second, reducing overall flow resistance through an inverse design approach. The optimized structure is experimentally validated against randomly designed comparative structures. The results demonstrate that the optimized structure achieves a comprehensive performance improvement ranging from 1.54 to 4.47 times over comparative structures. Furthermore, within the scope of this study, the optimized configuration reduces the pressure drop by 23 %–81 % while maintaining high heat transfer efficiency. This research contributes to the development of optimized microchannel array designs for active thermal management systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109882"},"PeriodicalIF":4.9,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143685490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuyang Bian , Xue Liu , Jiayue Zheng , Yanqi Diao , Weixing Zhou , Leonid Yanovskiy
{"title":"Numerical investigation on thermal insulation effect by coolant layer in performance of transpiration cooling","authors":"Yuyang Bian , Xue Liu , Jiayue Zheng , Yanqi Diao , Weixing Zhou , Leonid Yanovskiy","doi":"10.1016/j.ijthermalsci.2025.109856","DOIUrl":"10.1016/j.ijthermalsci.2025.109856","url":null,"abstract":"<div><div>The principle of transpiration cooling involves the internal convective heat transfer within the porous medium and the external thermal insulation by the coolant layer. This work quantitatively analyzed the insulation effect to deeply understand the mechanism of transpiration cooling. The average heat absorption power ratio is 1.12 under the 0.8 % injection ratio, indicating a greater contribution of thermal insulation to the performance of transpiration cooling. An increase in the injection ratio enhances the thermal insulation effect at the end of the porous medium, and the maximum heat absorption power ratio reaches 3.65 at the injection ratio of 0.9 %. Although a change in the mainstream Mach number leads to an overall alteration in the heat absorption power of both aspects, the average heat absorption power ratio of thermal insulation to convective heat transfer improves as the Mach number rises. The thermal insulation effect weakens with an increase in shock wave intensity. An exponential functional relationship exists between the average thermal insulation effect and the wedge angle. Under a wedge angle of 12°, the contribution of thermal insulation is less than that of the convective heat transfer in the porous medium, and the heat absorption power ratio drops to 0.52.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109856"},"PeriodicalIF":4.9,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu Han , Xiepeng Sun , Yong Yang , Xiaotao Chen , Jiang Lv , Xuehui Wang , Xiaolei Zhang , Longhua Hu
{"title":"An experimental study of wall smoke pattern characteristics adjacent to fire source","authors":"Yu Han , Xiepeng Sun , Yong Yang , Xiaotao Chen , Jiang Lv , Xuehui Wang , Xiaolei Zhang , Longhua Hu","doi":"10.1016/j.ijthermalsci.2025.109865","DOIUrl":"10.1016/j.ijthermalsci.2025.109865","url":null,"abstract":"<div><div>Confined fires within buildings pose significant risks to urban safety and the environment. Based on the interpretation and analysis of fire pattern, fire investigation is an important aspect for preventing fires and protecting lives and properties. Wall fire plume smoke pattern, as one of the fire patterns caused by fire thermal effect, plays a big role in the fire investigation of building fire, so the study is of great significance to fire investigation and safety development. This paper presents an experimental investigation focusing on the effects of various burner dimensions and heat release rates on the wall fire plume smoke pattern characteristics, as well as the relationship between it and wall fire plume characteristic parameters. Major findings are: (1) The symmetrical smoke pattern from fuel burning first incurves, then spreads outward, finally decreases to the centreline gradually. (2) The smoke pattern region increases as heat release rate increasing and burner dimension decreasing. (3) A dimensionless model of wall fire plume smoke pattern is proposed, associated with burner dimension, heat release rate, flame height and temperature, by which, the parameters in the history of fire can be learned to help fire scene reconstruction. The findings of this study contribute to understanding the evolution of smoke patterns produced by gaseous fuels and support advancements in experimental fire research and accident investigations.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109865"},"PeriodicalIF":4.9,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Multi-objective optimization of double-layer microchannel heat sink with trapezoidal cross-sections based on computational fluid dynamics","authors":"Rafat Mohammadi, Vahid Dadras","doi":"10.1016/j.ijthermalsci.2025.109879","DOIUrl":"10.1016/j.ijthermalsci.2025.109879","url":null,"abstract":"<div><div>This study presents a multi-objective optimization of a trapezoidal double-layer microchannel heat sink (TDL-MCHS) to minimize both thermal resistance and pumping power. A three-dimensional fluid-solid conjugate heat transfer model, coupled with a multi-objective genetic algorithm, was employed. The optimization considered five design variables, including the flow rate ratio between the upper and lower channels and four geometric parameters related to the channel cross-sections. A parametric study explored the design space, and response surface approximation was applied to improve computational efficiency. The results showed that the optimized TDL-MCHS achieved up to a 42 % reduction in thermal resistance, though at the cost of a significant increase in pumping power. Conversely, minimizing pumping power by 42 % led to a 4 % reduction in thermal resistance. The Pareto-optimal front highlights the trade-offs between thermal performance and energy consumption, providing valuable insights for the efficient design of TDL-MCHSs in electronic cooling applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109879"},"PeriodicalIF":4.9,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143645126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Study on solar radiation transfer model of double skin façade with spray aerosol","authors":"Yanjin Wang, Fangfang Wang, Jintao Xiong","doi":"10.1016/j.ijthermalsci.2025.109875","DOIUrl":"10.1016/j.ijthermalsci.2025.109875","url":null,"abstract":"<div><div>Spraying droplets into the cavity of the double skin façade can improve its thermal performance. However, the spray system is opened, the mist droplets (aerosols) dispersed in the cavity alter the transmission mechanism of solar radiation through the double skin façade. This study develops a solar radiation transfer model for double skin facade with spray aerosol based on the Mie scattering theory and the net radiation method. The model calculates the transmittance, reflectance, and absorptance of the double skin façade with spray aerosol. Experimental validation shows good agreement with the model, with a maximum error of approximately 11.2 % for solar heat gain. Additionally, this study examines key factors that influence the optical properties of the double skin facade with spray aerosol, including aerosol particle number concentration, average radius, cavity distance, and incidence angle. The results indicate that total transmittance decreases as aerosol concentration and average radius increase. However, when the concentration exceeds 600 particles/cm<sup>3</sup> and the average radius exceeds 15 μm, the reduction in transmittance becomes less pronounced. Changes in cavity distance and incidence angle have a minimal effect on transmittance at high aerosol concentrations. By controlling aerosol concentration and average radius, solar heat gain can be effectively reduced. The model accurately describes solar radiation transmission in real conditions, helping assess the optical and thermal properties of double skin façades with spray aerosol.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109875"},"PeriodicalIF":4.9,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}