International Journal of Thermal Sciences最新文献

{"title":"Performance analysis of Gallium-based liquid metal as thermal interface material for chip heat dissipation","authors":"Baihong Liu ,&nbsp;Wenfeng Gao ,&nbsp;Liangfei Duan ,&nbsp;Qiong Li ,&nbsp;Shuai Gong ,&nbsp;Rujian Li ,&nbsp;Jie Zhang","doi":"10.1016/j.ijthermalsci.2025.110121","DOIUrl":"10.1016/j.ijthermalsci.2025.110121","url":null,"abstract":"<div><div>Effective heat dissipation is crucial for reducing chip operating temperatures and improving energy efficiency in data centers. As chip heat generation continues to rise dramatically, interfacial thermal resistance has emerged as a significant bottleneck for heat dissipation. Therefore, identifying thermal interface materials (TIMs) with high thermal conductivity and low thermal contact resistance is essential. In this study, we propose using a liquid metal alloy composed of 75 % gallium and 25 % indium as a TIM, which boasts a high thermal conductivity of 26.6 W/m·K and a low thermal resistance of 2.8 mm²·K/W. A theoretical mathematical model was developed to characterize interfacial heat transfer. Experiments were conducted to compare the heat dissipation performance of liquid metal with that of thermal grease used as TIMs. Furthermore, numerical simulations were performed to analyze the effects of heating power, TIM thickness, and thermal interface area on the chip heat dissipation performance. The experimental results show that liquid metal significantly outperforms thermal grease as a TIM, with the heat source temperature being 9.8 °C lower for liquid metal at a heating power of 90 W. Numerical simulations reveal a linear increase in heat source temperature with rising heating power. Moreover, both reducing the TIM thickness and increasing the thermal interface area improve heat dissipation performance. Specifically, when the TIM thickness was reduced from 2 mm to 0.2 mm and the thermal interface area was increased from 6.25 cm² to 16 cm², the heat source temperature was decreased by 8 % and 35.9 %, respectively. This study highlights the potential of liquid metal as a TIM for the thermal management of high-power-density chips, such as CPUs, GPUs, and AI accelerators, while providing valuable insights for enhancing the design of chip cooling systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110121"},"PeriodicalIF":4.9,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144549205","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":"Thermal dissipation enhancement on central impinging jet double layer microchannel heat sinks verified by 3D printing method","authors":"Xingran Li ,&nbsp;Peng Li ,&nbsp;Xinyue Lan ,&nbsp;Yung-Yu Ku ,&nbsp;Han Shen","doi":"10.1016/j.ijthermalsci.2025.110127","DOIUrl":"10.1016/j.ijthermalsci.2025.110127","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The continuous development of electronic chips and devices towards miniaturization and high integration has led to an increase in heat generation, and traditional cooling methods can no longer meet the needs of high-power electronic chips. Based on this background, this study proposes a novel design to improve the thermal performance of microchannel heat sinks for high-performance electronic cooling applications. This double-layer microchannel heat sink with integrated impinging jet and rectangular fins, called impinging jet-nested double-layer microchannel heat sink with rectangular fins (IDN-MHS-RF), is fabricated using Selective Laser Melting (SLM) technology. The design aims to address the limitations of conventional microchannel heat sinks, especially in terms of cooling efficiency under high heat flux conditions. To validate the simulation results, experimental tests were conducted using 3D printed heat sink specimens. Numerical simulations and experimental validation of the expected results agree, confirming the accuracy of the model, and both simulations and experiments show that the IDN-MHS-RF significantly improves the thermal performance when compared to a double-layer straight microchannel heat sink (DSMCHS) and the impinging jet-nested double-layer microchannel heat sink (IDN-MHS). The Reynolds numbers tested ranged from 138.20 to 580.44. The maximum pressure drop of IDN-MHS-RF is 7.33 kPa at Reynolds number 580.44, which is 4.16 and 1.45 kPa higher than that of DSMCHS at 3.17 kPa and IDN-MHS at 5.98 kPa. The introduction of fins and impinging jets enhances the mixing and heat transfer of fluids, which inevitably leads to an increase in the pressure drop, but at the same time, it also significantly improves the thermal performance, with a maximum Nussellt number of 64.44, which is 90.76 % and 27.45 % higher than that of DSMCHS at 33.78 and 50.56 respectively. Its maximum Nusselt number is 64.44, which is 90.76 % and 27.45 % higher than that of 33.78 and 50.56 for DSMCHS and IDN-MHS, respectively. Taking DSMCHS as a reference1, the integrated heat transfer coefficient of IDN-MHS is 1.24, whereas the integrated heat transfer coefficient of IDN-MHS-RF2 is as high as 1.50, which indicates a significant improvement in the overall cooling efficiency compared with DSMCHS and IDN-MHS. In addition, the optimal fin spacing is IDN-MHS-RF2 (rectangular fin spacing of 2 mm), the maximum temperature is only 318.11 K, which is 5.15 and 1.10 K lower than that of DSMCHS and IDN-MHS, respectively, and the maximum temperature difference at the bottom is only 1.22 K, which is 2.11 and 0.54 K lower than that of DSMCHS and IDN-MHS, respectively, so that the cooling effect and thermal uniformity are optimized. The cooling effect and thermal uniformity are optimized, and the relative balance between thermal resistance and flow resistance is realized. These findings show that IDN-MHS-RF can effectively reduce substrate temperature and improve therm","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110127"},"PeriodicalIF":4.9,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557071","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":"A new three-edge bone drill designed to reduce mechanical and thermal damage","authors":"Shaokang Song ,&nbsp;Jun Zhao ,&nbsp;Qian Li ,&nbsp;Anhai Li ,&nbsp;Xianshun Sun ,&nbsp;Shihua Zhang ,&nbsp;Junfu Liu","doi":"10.1016/j.ijthermalsci.2025.110128","DOIUrl":"10.1016/j.ijthermalsci.2025.110128","url":null,"abstract":"<div><div>The geometric modification of bone drills is an important way to reduce damage to bone tissue during surgical procedures. This study designed a new three-edge bone drill to improve the efficiency of cortical bone drilling and reduce the damage to bone tissue. Compared with the common two-edge bone drill, the three-edge bone drill design reduces the uncut thickness per tooth (feed per tooth) under the same drilling conditions, and can maintain high drilling stability and low mechanical damage even under high feed rate and low spindle speed (low thermal damage) conditions. The drilling performance of the three-edge bone drill is investigated via a comprehensive cortical bone drilling experiment in comparison with that of a common two-edge bone drill. The experimental results show that compared with the two-edge drill bit, the three-edge drill reduces the drilling force by 8.51 %–22.6 %, the drilling force fluctuation is reduced by 8.12 %–20.93 %, the maximum drilling temperature is reduced by 4.23 %–12.24 %, the thermal damage area is reduced by 11.04 %–31.34 %, and the hole wall roughness is reduced by 10.55 %–26.11 %. This study provides an efficient and low-damage solution for orthopedic surgery.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110128"},"PeriodicalIF":4.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534455","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":"Enhanced heat transfer of PCM-based heat sink augmented with plate-fins and hybrid nanoparticles for electronics cooling","authors":"Adeel Arshad ,&nbsp;Mark Jabbal ,&nbsp;Yuying Yan","doi":"10.1016/j.ijthermalsci.2025.110107","DOIUrl":"10.1016/j.ijthermalsci.2025.110107","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Passive cooling technologies based on phase change material (PCM) reveal as emerging technique for thermal management of electronic components efficiently. Therefore, the current study explores the combined effect of hybrid nanoparticles (HNPs), plate-fins, and PCM integrated in a heat sink for both heating and cooling operation modes. As, PCM exhibits the lower thermal conductivity which makes it unfavourable for rapid heat transfer modes especially while solidification phase. Therefore, the novel incorporation of higher thermal conductive fins and hybrid nanoparticles with PCM are numerically studied to promote the heat transfer rate while melting and solidification phases. HNPs of graphene nanoplatelets (GNP)-copper (Cu) are dispersed in PCM of varying loading content (2%&lt;span&gt;&lt;math&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; &lt;span&gt;&lt;math&gt;&lt;mi&gt;φ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; &lt;span&gt;&lt;math&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;6%) to develop hybrid nanocomposite phase change material (HNcPCM). Similarly, the number of plate-fins are varied by changing their volume fraction (0%&lt;span&gt;&lt;math&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; &lt;span&gt;&lt;math&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; &lt;span&gt;&lt;math&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;20%). Under a constant heat flux, the thermal performance is evaluated under transient conditions for both qualitative and quantitative aspects. Results exhibit the rapid enhancement in heat transfer rate during melting/solidification and a lower heat sink base temperature is revealed. A reduction in heat sink base temperature is reduced by 4.0% and 5.35% with 10% and 20%, respectively, compared to 0% without HNPs. However, this reduction is achieved of 0.63%, 1.10% and 1.5% with 2%, 4% and 6% of &lt;span&gt;&lt;math&gt;&lt;mi&gt;φ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; hybrid nanoparticles, respectively, with 10% compared to 0%. The heat storage/release capacity (&lt;span&gt;&lt;math&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) and heat storage/release density (&lt;span&gt;&lt;math&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) exhibit the decreasing trend because of increase in total mass of HNcPCM-Fins. A reduction in &lt;span&gt;&lt;math&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; is obtained of 24.18% and 23.1%, respectively, for 10% during melting phase in latent-heat state. The addition of plate-fins and GNP-Cu HNPs present a uniform melting/solidification phenomenon of HNcPCM inside the heat sink and a rapid melting/solidification rate and phase completion time are obtained, which understands the fluctuating operating modes. The higher enhancement in temperature response rate is obtained in case of plate-fins compared to the addition of GNP-Cu HNPs for both melting and solidification phases. The enhancement in heat transfer (&lt;span&gt;&lt;math&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;́&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/math&gt;&lt;/span&gt;) and heat transfer density (q́) is obtained of 12.23% and 13.84% for 10%, respectively, during cooling phase compared to 0% in latent-heat state. The optimum volume fractions of GNP-Cu HNPs and plate-fins are found of 2% and 10%, respectively, for effective thermal man","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110107"},"PeriodicalIF":4.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144549201","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":"Optimization thermal performance of ship infrared suppression devices via dual-layer water mist cooling","authors":"Zhuo Zeng ,&nbsp;Nenglin Yuan ,&nbsp;Yitao Zou ,&nbsp;Hong Shi","doi":"10.1016/j.ijthermalsci.2025.110126","DOIUrl":"10.1016/j.ijthermalsci.2025.110126","url":null,"abstract":"<div><div>To enhance the performance of conventional infrared suppression systems, this study proposes a dual-layer spray system that leverages staggered water mist coverage to enhance the synergy between water mist cooling and airflow entrainment, significantly improving IRS performance. Using computational fluid dynamics (CFD), key parameters including the radial distance of spray injectors from the centerline (<em>l</em>_<em>n</em>), axial spacing between layers (<em>d</em>_<em>n</em>), and horizontal angular offset (<em>φ</em>) were systematically optimized. The results indicate that optimizing <em>l</em>_<em>n</em> to 0.8 m significantly enhances droplet dispersion while minimizing kinetic energy loss, thereby improving exhaust cooling efficiency. When <em>d</em>_<em>n</em> is 100 mm and <em>φ</em> to 30°, the system achieves optimal performance, reducing the outlet temperature of the mixing diffuser by up to 82.48 K, and effectively controlling the wall-temperature rise caused by airflow compression. Furthermore, this study reveals that momentum exchange between entrained airflow and water mist may cause high-temperature fluid to impact the wall, increasing local wall-temperature. The study provides an effective strategy to balance exhaust cooling and wall-temperature control, advancing IRS technology for naval applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110126"},"PeriodicalIF":4.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144549203","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":"Topological optimization design of micro-pin fin heat sinks for high heat flux cooling application","authors":"Huizhu Yang ,&nbsp;Zehui Wang ,&nbsp;Yanhong Jiang ,&nbsp;Yibin Xie ,&nbsp;Andong Wang ,&nbsp;Binjian Ma ,&nbsp;Xiaozhou He","doi":"10.1016/j.ijthermalsci.2025.110102","DOIUrl":"10.1016/j.ijthermalsci.2025.110102","url":null,"abstract":"<div><div>Micro-pin fin heat sinks (MPFHSs) have shown remarkable advantages for high heat flux cooling applications due to their effectiveness in enhancing thermal performance. Topology optimization further yields more compact and efficient thermal designs. In this study, a variable density topology optimization is developed to figure out the optimal material distribution and micro-pin fin geometric structures in a liquid-cooled heat sink. The topological methodology is firstly validated by comparing the 2D topology optimization with the 3D numerical simulation. The effect of fluid volume fraction <em>V</em>_f, porosity <em>ε</em> and diameter <em>D</em> of the micro-pin fin array is then discussed to achieve the optimal design parameters. Finally, the superiority and potential of the topology-optimized MPFHS are thoroughly discussed by comparing it with two traditional MPFHS: one without a main channel and one with six straight main channels. The results show that the optimal design parameters are <em>V</em>_f = 17.5 %, <em>ε</em> = 0.5 and <em>D</em> = 300 μm. Compared to the two traditional designs, the optimized MPFHS achieves 89 % and 97.6 % reductions in pumping power while achieving the same thermal performance. Besides, the optimized MPFHS can effectively manage a heat flux of 400 W/cm2 while maintaining a total pumping power of just 118.9 W. These results are of great significance to the design of advanced MPFHS for chip cooling.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110102"},"PeriodicalIF":4.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534454","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":"Three-dimensional distribution of liquid film thickness and heat transfer coefficient in horizontal flat tube falling film evaporation","authors":"Wenjie Deng ,&nbsp;Zhenhua Quan ,&nbsp;Chunduo Song ,&nbsp;Chenyang Du ,&nbsp;Lincheng Wang ,&nbsp;Yaohua Zhao","doi":"10.1016/j.ijthermalsci.2025.110087","DOIUrl":"10.1016/j.ijthermalsci.2025.110087","url":null,"abstract":"<div><div>Horizontal tube falling film evaporators (HTFFEs) are widely used in the sustainable energy sector due to their superior heat transfer performance. To further enhance heat and mass transfer efficiency and improve energy utilization, a novel horizontal flat tube falling film evaporator (HFTFFE) is proposed. Numerical modeling of the HFTFFE process was conducted using the Volume of Fluid (VOF) model to analyzed the three-dimensional flow characteristics, liquid film thickness (<em>δ</em>), and heat transfer coefficient (<em>h</em>), with comparisons to the HTFFE. The results show that the circumferential falling film flow processes through five stages: free falling, liquid film impact, free flow, vertical wall falling film, and complete flow. Axially, the liquid film exhibits a pattern of peaks and valleys, with <em>δ</em> and <em>h</em> displaying consistent trends. Circumferentially, <em>δ</em> decreases rapidly at first, then stabilizes, while its axial variation remains minimal. The liquid film impact zone records the highest <em>δ</em> and <em>h,</em> whereas the complete flow zone shows the lowest values. Increasing the Spray Reynolds number (<em>Re</em>) significantly raises <em>δ</em> at the crest. The <em>Re</em>, heat flux density, and spray height all positively influence <em>h</em>. Compared to a traditional HTFFE of equivalent cross-sectional perimeter, the HFTFFE shortens flow time by 10.3 %, reduces average liquid film thickness by 11.4 %, and increases the average heat transfer coefficient by 5.1 %. These findings highlight the superior flow and heat transfer performance of the HFTFFE, making it a promising option for sustainable energy applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110087"},"PeriodicalIF":4.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534537","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":"Experimental study on supercritical CO2 heat transfer and field comparisons inside mini-channel under local heat flux from bottom and top walls","authors":"Gang Zeng ,&nbsp;Lin Chen ,&nbsp;Haizhuan Yuan ,&nbsp;Yanping Huang","doi":"10.1016/j.ijthermalsci.2025.110038","DOIUrl":"10.1016/j.ijthermalsci.2025.110038","url":null,"abstract":"<div><div>This study experimentally investigated and compared the transient boundary heat transfer behavior of supercritical CO₂ (sCO₂) in a mini-channel subjected to localized heating from the top and bottom walls. A pixelated phase-shifting interferometer was employed to capture the transient field data, enabling the extraction of density field for quantitative analysis the thermal boundary layer affected by the combination of buoyancy effects and local heating. It has been found that: (1) In top-heated cases, the heated zone contracts due to secondary flow directed towards the upper wall, but is expanded in the bottom-heated cases as the buoyancy-driven fluid rises from the lower wall into the main-flow; (2) Rapid thermal variations strongly intensifies the bottom convective mixing, with increased <em>Nu</em> value, but slower and weaker in the top-heated cases; Local thermal stratification patterns and thermal stagnation deteriorate the heat transfer, yielding a lower <em>Nu</em> level; (3) Increasing thermal load amplifies local stratification due to thermal acceleration, as evidenced by the density-temperature shifts of 1.2 kg/m³, 0.017 K for <em>q</em> = 8.79 kW/m², compared to 0.6 kg/m³, 0.006 K for <em>q</em> = 0.55 kW/m². Secondary flow redistributes thermal energy, reversing a substantial portion of initially downward-flowing sCO₂ into upward motion.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110038"},"PeriodicalIF":4.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144549202","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":"Influence of height difference on thermal performance and flow stability of loop thermosyphon equipped with vertically placed flat evaporator for IGBT module cooling","authors":"Hengxuan Xu ,&nbsp;Xiangji Guo ,&nbsp;Shaowei Yang ,&nbsp;Fengyi Tang ,&nbsp;Bo Zhang ,&nbsp;Kang Wang","doi":"10.1016/j.ijthermalsci.2025.110124","DOIUrl":"10.1016/j.ijthermalsci.2025.110124","url":null,"abstract":"<div><div>This study presents a comprehensive experimental investigation into the thermal-hydraulic performance and flow dynamics of a loop thermosyphon system incorporating a vertically oriented flat evaporator designed for insulated gate bipolar transistor (IGBT) module cooling. The effects of critical operational parameters, namely liquid filling ratio (31 %–92 %), heat load (100–900 W), and height difference between evaporator and condenser (0 cm, 20 cm, 40 cm, and 60 cm), on heat transfer characteristics, temperature uniformity, and start-up behavior were systematically examined. Results reveal that increasing the height difference enhances the gravitational driving force, thereby expanding the operational heat load range and reducing the average evaporator temperature; however, it concurrently exacerbates temperature non-uniformity due to complex two-phase flow instabilities. Notably, an optimal filling ratio near 73 % was identified at zero height difference, where the system exhibits heightened sensitivity to filling variations and limited natural circulation capability. Detailed pressure measurements elucidate the interplay between liquid column height and flow resistance, highlighting a saturation phenomenon in driving pressure at elevated heat loads. The study further uncovers transient gas blockage during start-up, manifesting as short-lived dry-up and temperature oscillations, which detrimentally affect system stability. These phenomena are attributed to the coupled effects of liquid film dynamics, bubble behavior, and gravitational forces within the confined geometry of the flat evaporator. The findings provide critical insights into the underlying physical mechanisms governing loop thermosyphon operation with flat evaporators and offer practical guidelines for optimizing design parameters to achieve enhanced thermal management of high-power electronic devices.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110124"},"PeriodicalIF":4.9,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522898","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":"Experimental investigation of cross-flow heat exchangers with helical fins: Performance analysis via RSM and ANN","authors":"Mehmet Yoladi ,&nbsp;Eda Feyza Akyurek ,&nbsp;İsak Kotcioglu","doi":"10.1016/j.ijthermalsci.2025.110111","DOIUrl":"10.1016/j.ijthermalsci.2025.110111","url":null,"abstract":"<div><div>In this study, the thermal and flow characteristics of cross-flow heat exchangers with helical fins were analyzed experimentally and numerically. The Box-Behnken Design (BBD) was used to examine the effects of air velocity, air inlet temperature, and water flow rate on key performance parameters including Nusselt number (<em>Nu</em>), Reynolds number (Re), friction factor (f), Colburn j factor, and Stanton number (St). Experimental results showed that increasing the Reynolds number improved heat transfer, with <em>Nu</em> increasing by up to 35 % and f decreasing by approximately 70 %. Among the variables, air velocity (x₃) was the most dominant, while water flow rate had a minor effect. Experimental results were also compared with ANSYS Discovery simulations, which revealed a temperature deviation of 15 % and a pressure drop error of 7.9 %, highlighting the limitations of simplified turbulence models. RSM regression models showed high accuracy, especially for Reynolds number (R² = 1.00, p &lt; 10⁻¹²), while models for <em>Nu</em> (R² = 0.899), f (R² = 0.971), and j (R² = 0.940) showed minor deviations due to turbulence-induced nonlinearities. Artificial Neural Networks (ANN) yielded even higher predictive accuracy, particularly for f (R² = 0.9996), <em>Nu</em> (error: 6.6 %), and j (error: 7.3 %), confirming their potential in thermal modeling. Overall, air velocity was the most influential parameter, and the hybrid use of RSM and ANN provided a strong framework for heat exchanger optimization. Future work should focus on AI-based optimization techniques and advanced CFD analysis.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"218 ","pages":"Article 110111"},"PeriodicalIF":4.9,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522901","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}