Case Studies in Thermal Engineering最新文献

{"title":"Enhancing thermal performance of two-phase closed thermosyphons by inhibiting geyser boiling: Synergistic effects of carbon nanotube nanofluids","authors":"Seungyeop Baek ,&nbsp;Cheol Park ,&nbsp;Seunghyeon Lee ,&nbsp;Yonmo Sung","doi":"10.1016/j.csite.2025.105764","DOIUrl":"10.1016/j.csite.2025.105764","url":null,"abstract":"<div><div>Two-phase closed thermosyphons (TPCTs) are passive heat transfer devices utilized in various applications owing to their simple, effective heat transfer ability. However, their thermal performance and structural integrity are undermined by aspects such as temperature fluctuations associated with geyser boiling. To resolve these issues, the present study was aimed at exploring the potential of carbon nanotube (CNT) nanofluids to enhance thermal conductivity and alter the surface wettability between the CNT nanofluid and the inner surface of the evaporation section, thus suppressing temperature fluctuations and improving the thermal performance of the TPCT. Specifically, the addition of 0.5 wt% CNTs to distilled water (DW) led to an approximately 3.35 % enhancement in thermal conductivity in the temperature range of 293.15–313.15 K. In terms of wettability, the addition of 0.5 wt% CNTs to DW increased the contact angle on a homogeneous glass surface while decreasing it by 13.37 % on an inhomogeneous surface with randomly deposited CNTs, achieving greater hydrophilicity. In the TPCT operation experiments, DW exhibited aperiodic and drastic temperature fluctuations at inclination angles of 90°, 60°, and 30°; in contrast, the 0.5 wt% CNT nanofluid showed stable temperature profiles, significantly reducing the maximum and average temperature differences between the bottom and top of the evaporation section. Even with temperature fluctuations, the overall thermal resistance reduced by up to 9.48 %, whereas the heat transfer coefficient increased by up to 19.66 %. These results confirm that the addition of 0.5 wt% CNTs to DW drastically improved the thermal performance of the TPCT.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105764"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of core window height on thermal characteristics of dry-type transformers","authors":"Kamran Dawood ,&nbsp;Seda Kul","doi":"10.1016/j.csite.2025.105746","DOIUrl":"10.1016/j.csite.2025.105746","url":null,"abstract":"<div><div>Elevated temperatures in transformer windings and cores pose a significant risk of damage to power transformers. The objective of this work is to analyze the influence of core window dimensions on the thermal efficiency of power transformers. Analytical approaches are limited in their ability to consider the impact of core window dimensions on the transformer's thermal behavior. Conversely, experimental methods are both expensive and time-consuming. To overcome these constraints, this work assesses and optimizes the temperature distribution in dry-type power transformers using finite element models, specifically examining the impact of the core window. The thermal model treats core and winding losses as sources of heat generation. Four different transformers, with varying heights of the transformer core window, have been modeled to assess the impact of window height on the thermal conditions of the transformers. The simulation findings indicate that variations in core window height have a significant impact on the transformer's thermal properties. By comparing the model's predictions of short-circuit impedance with experimental data, this study demonstrates the model's capability to reliably estimate parameters influenced by core window variations, thereby validating its usefulness.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105746"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improved prediction model for ceiling maximum smoke temperature in the uphill tunnel fires using water spray system","authors":"Jie Wang ,&nbsp;Dan Huang ,&nbsp;Yanlong Song ,&nbsp;Kaihua Lu","doi":"10.1016/j.csite.2024.105739","DOIUrl":"10.1016/j.csite.2024.105739","url":null,"abstract":"<div><div>Stack effect of sloped tunnel and cooling effect and dragging force induced by water spray system change smoke temperature which is a serious threat to the stability and integrity of the tunnel structure. Smoke temperature profile is investigated under various heat release rates (10 MW, 15 MW, and 20 MW), water spray flow rates (0, 100, 200, 300, and 400 L/min), and atomizing angles (0°, 30°, 60°, 90°, 120°, and 150°) at a constant slope of 3 %. The results reveal that the water spray system significantly suppresses the maximum temperature rise, particularly in the downstream area adjacent to the fire source, where the aggregation of smoke and the induced stack effect intensify the impact. Several dimensionless maximum temperature rise models were developed, incorporating a <em>Q∗</em>, <em>q</em>, and <em>θ</em>. The dimensionless maximum temperature rise adheres to an exponential decay function relative to the distance from the fire source, the index is −0.37, indicating a direct proportionality. This relationship is influenced by the heat absorption capacity of water spray droplets, which is a function of both the flow rate and the atomizing angle. Although the atomization angle has a minimal effect on the total heat absorption, it changes the spatial distribution of heat absorption, thereby affecting the smoke temperature curve. The flow rate is more important than the atomization angle in controlling smoke temperature. This predictive model is a reliable tool for estimating the maximum temperature rise in the upstream and downstream areas of the fire source under various water spray conditions.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105739"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142940001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrated 3E impacts of photovoltaic systems: A comparative study of panels and windows","authors":"Na Zhao ,&nbsp;Jia Zhang ,&nbsp;Chao Ding","doi":"10.1016/j.csite.2024.105736","DOIUrl":"10.1016/j.csite.2024.105736","url":null,"abstract":"<div><div>This paper evaluates the integrated benefits of photovoltaic (PV) building systems in terms of energy, economy, and environment, providing a scientific basis for low-carbon sustainable buildings. Using the renovation project of a hospital in Ordos, Inner Mongolia, as a case study, we simulated energy consumption and power generation of PV-integrated buildings with EnergyPlus and JEPlus. The study considers three retrofit scenarios: installing PV panels on the exterior walls and roofs; replacing external windows with PV windows; combining both PV panels and windows. The impact on building energy consumption, carbon emissions, and economic costs was examined under various window-to-wall ratios (WWR) and PV power capacities. A multi-objective optimization analysis was performed using the TOPSIS method to identify the most balanced solutions. The results indicate that optimal PV system configurations should balance energy consumption, carbon emissions, and costs. For scenario 1, a WWR of 0.4 and 100 W power yield the best performance. For scenario 2, a WWR of 0.2 with type 3 PV windows is optimal. For scenario 3, a WWR of 0.2, 300 W power, and type 1 PV windows effectively reduce energy consumption and carbon emissions while maximizing economic benefits.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105736"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142940002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A comprehensive numerical study exploring the significance of thermally reactive bioconvection in Falkner-Skan flow of Williamson nanomaterials influenced by activation energy and buoyancy forces","authors":"M. Israr Ur Rehman ,&nbsp;Haibo Chen ,&nbsp;Aamir Hamid ,&nbsp;Wu Qian ,&nbsp;Refka Ghodhbani ,&nbsp;Mohamed Hussien","doi":"10.1016/j.csite.2025.105785","DOIUrl":"10.1016/j.csite.2025.105785","url":null,"abstract":"<div><div>Heat and mass transport performance is greatly improved in a variety of industrial, engineering, and technological applications by the advanced thermal properties of nanomaterials, which are enhanced by chemical reactions, nonlinear thermal radiation, nonuniform heat sources/sinks, Arrhenius kinetic energy, and induced electromagnetic forces. The analysis is further improved by adding thermophoretic diffusion and Brownian motion to the energy and concentration equations Bio-fuels, enzymes, industry, bio-sensors, petroleum, and a number of other novel biotechnological features are also influenced by the bioconvective mechanisms in nanomaterials. Motivated by these properties, this study investigates the rheological behavior of non-Darcian Williamson nanomaterials interacting with motile microorganisms, driven by Falkner-Skan wedge surfaces. Similarity transformations are used to convert the system of partial differential equations into a system of ordinary differential equations, which are then numerically solved using the Runge–Kutta–Fehlberg (RKF-45) method. After the system has been altered, the physical parameters that result are examined and shown graphically. The raising valuation of wedge angle parameter diminished the velocity and friction drag. Moreover, higher thermal radiation and electric parameter also escalate the thermal field. Nanoparticle concentration is improving function via Arrhenius activation energy.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105785"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hygrothermal performance of well-insulated wood-frame walls in Baltic climatic conditions","authors":"Anatolijs Borodinecs ,&nbsp;Vladislavs Jacnevs ,&nbsp;Lakatos Ákos ,&nbsp;Staņislavs Gendelis","doi":"10.1016/j.csite.2025.105772","DOIUrl":"10.1016/j.csite.2025.105772","url":null,"abstract":"<div><div>This study investigates the hygrothermal performance of wood-frame walls in the Baltic region under varying moisture loads, comparing bio-based and conventional insulation materials. The research combines experimental climate chamber testing with DELPHIN simulations to assess moisture risk mitigation, energy efficiency and mould growth resistance. The results highlight that bio-based insulations, such as wood fibre, outperform conventional materials due to higher vapour diffusion resistance (μ = 5) and superior moisture-buffering capacity. For instance, wood fibre insulation reduced the RHT-index by 30.6 % compared to mineral wool while maintaining mould indices below 0.71. Furthermore, the study identifies optimal wind-to-vapour barrier ratios, such as 1:2 for cellulose insulation, that mitigate mould risks in high-moisture conditions. The findings advocate for adopting vapour-open wall assemblies and bio-based materials to enhance building durability, energy efficiency and moisture resilience in cold climates.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105772"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance improvement of transcritical vapor generator by a novel double-heated annular configuration","authors":"Yue Pan ,&nbsp;Yuling Zhai ,&nbsp;Zhouhang Li ,&nbsp;Nan Hu","doi":"10.1016/j.csite.2025.105782","DOIUrl":"10.1016/j.csite.2025.105782","url":null,"abstract":"<div><div>A novel double-heated annular configuration is proposed for the vapor generator of transcritical CO₂ power cycle. The idea originated from that an annulus is more resistant to the deterioration of supercritical heat transfer than a circular tube, and in this work attempts were made on adjusting the heating mode to potentially further improve the thermal efficiency. Numerical results from the present well-validated model show that in forced convection flow, the introduction of outside heating surprisingly increase the heat transfer coefficient at the inner side, with a maximum relative rise of 17 % to that with only inner heating. This enhancement owes to the more favorable radial profiles of fluid thermophysical properties, with specific heat and Prandtl number near the inner side being significantly increased by the outer heating. In mixed convection flow, the double-side heating improves the inside heat transfer when the outside heat flux is below 40 % of the critical heat flux in circular tubes, otherwise it may impair heat transfer, the extent of which depends on the specific operating conditions and geometric parameters. As the outside heat flux increases, wall temperatures at both annular sides gradually evolve into a similar profile to that of circular tubes. However, even when both sides are subjected to the critical heat flux, the peak wall temperatures are still 2–30 K lower than those of circular tubes. The heat transfer deterioration is not exacerbated even at the worst scenario, demonstrating the superior anti-deterioration performance of the double-heated annular configuration. Overall, the novel configuration can effectively improve supercritical heat transfer once designed as recommended, substantiating itself as a feasible option for transcritical heat exchangers.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105782"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design of an additively manufactured thermal solution for an axial flux switched reluctance motor","authors":"Martin Sarap ,&nbsp;Shalini Singh ,&nbsp;Ants Kallaste ,&nbsp;Ahmed Qureshi ,&nbsp;Hans Tiismus ,&nbsp;Toomas Vaimann ,&nbsp;Payam Shams Ghahfarokhi","doi":"10.1016/j.csite.2025.105805","DOIUrl":"10.1016/j.csite.2025.105805","url":null,"abstract":"<div><div>This study presents the design and evaluation of an additively manufactured thermal solution for an axial flux switched reluctance motor, aimed at enhancing its applicability in light unmanned aircraft propulsion. The primary objective is to optimize the motor's power-to-weight ratio by improving its thermal management through innovative heatsink designs. The methodology involves a comprehensive design procedure to dimension a conventional finned heatsink. The performance of the heatsink is experimentally tested under practical conditions using a motorette setup and cooling fans. Key findings indicate that the proposed thermal solution can enable very high current densities for an air-cooled electrical machine.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105805"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conjugate heat dissipation characteristics of concurrent flow of pure water/water-based nano-emulsion through a mini- and micro-channel stacked double-layer heat sink","authors":"C.J. Ho ,&nbsp;Jr-Wei Liao ,&nbsp;Bo-Lin Chen ,&nbsp;Saman Rashidi ,&nbsp;Wei-Mon Yan","doi":"10.1016/j.csite.2025.105799","DOIUrl":"10.1016/j.csite.2025.105799","url":null,"abstract":"<div><div>The main purpose of current study is to reduce the temperature gradient and pressure drop in the heat sinks by using a new double-layer mini/micro-channel stacked heat sink. In this numerical study, the conjugate heat dissipation characteristics of concurrent flow of pure water/water-based nano-emulsion through a mini- and micro-channel stacked double-layer heat sink is investigated. The potentials of pure water/phase change nanoemulsion in a mini- and micro-channel stacked double-layer heat sink for heat dissipation are compared with those for pure water in the single-layer microchannel heat sink. The effects of different parameters, such as flow rate ratio, total flow rate, heat flux, and concentration of the phase change nanoemulsion on the heating surface temperature suppression, pressure drop ratio, thermal resistance ratio, heating surface temperature uniformity index ratio, total heat transfer coefficient gain, and performance indexes are investigated. The three-dimensional velocity field in the channel is calculated by the pseudo-vorticity-velocity method, and the finite volume method is used to discrete the mathematical formulas. The numerical results showed that when the ratio of flow rate is 0.5, the total flow rate is 25.48 <span><math><mrow><msup><mtext>cm</mtext><mn>3</mn></msup></mrow></math></span>/min, and the heat flux is 25 W/ <span><math><mrow><msup><mtext>cm</mtext><mn>2</mn></msup></mrow></math></span>, the overall heat transfer coefficient of the mini- and micro-channel stacked double-layer heat sink with pure water/10 % mass fraction of phase change nanoemulsion as the coolants increases by 36.14 % compared with single-layer heat sink with pure water as the coolant. In addition, when the flow rate ratio is high and the total flow rate is low, the values of average and maximum thermal resistance ratios are greater than 1.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105799"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143061967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical simulation of Stephan blowing impacts on thermally laminated 3D flow of MHD trihybrid nanofluid with Soret and Dufour effects","authors":"Noureddine Elboughdiri ,&nbsp;Munawar Abbas ,&nbsp;Hamdi Ayed ,&nbsp;Abir Mouldi ,&nbsp;Nahid Fatima ,&nbsp;Dilsora Abduvalieva ,&nbsp;Mohamed Said ,&nbsp;Ibrahim Mahariq ,&nbsp;Ahmed S. Hendy ,&nbsp;Ahmed M. Galal","doi":"10.1016/j.csite.2024.105460","DOIUrl":"10.1016/j.csite.2024.105460","url":null,"abstract":"<div><div>The present work examines the Soret and Dufour significance on 3D flow of THNF (trihybrid nanofluid) over sheet with porous medium, heat radiation and Stephan blowing impacts using two different thermal conductivity models known as HCM (Hamilton-Crosser model) and YOM (Yamada-Ota model). A trihybrid nanofluid consisting of <span><math><mrow><mi>C</mi><mi>u</mi></mrow></math></span>, <span><math><mrow><mi>T</mi><mi>i</mi><msub><mi>O</mi><mn>2</mn></msub></mrow></math></span>, <span><math><mrow><mi>F</mi><msub><mi>e</mi><mn>3</mn></msub><msub><mi>O</mi><mn>4</mn></msub></mrow></math></span> and propylene glycol (<span><math><mrow><mrow><msub><mrow><msub><mi>C</mi><mn>3</mn></msub><mi>H</mi></mrow><mn>8</mn></msub><msub><mi>O</mi><mn>2</mn></msub></mrow><mo>)</mo></mrow></math></span> as the base liquid is utilized. Performance-wise, this suggested model contrasts the two well-known thermal conductivity THNF models, the YOM (Yamada-Ota model) and the HCM (Hamilton-Crosser model). An advanced model for 3D analysis for THNF (trihybrid nanofluid) through Stefan blowing is existing in the Current investigation. This sophisticated study is essential to improving heat transfer efficiency in industrial processes involving intricate fluid flows under magnetic fields, such as nuclear reactor cooling systems, electronic device cooling systems, and aeronautical engineering. By accurately forecasting the behavior of nanofluids, the model aids in the optimization of thermal management in these systems, enhancing system dependability and energy efficiency. The mathematical results of governing comparisons remain acquired through shelling method (Bvp4c). The YOM and MCM models are used to describe how certain physical characteristics (concentration, velocity, and thermal) affect the usual profiles. The velocity profile and rate of heat transmission rise as the Stephan blowing parameter is increased, but the thermal distribution decreases. The Yamada-Ota model outperforms the Hamilton-Crosser thermal conductivity model of THNF in terms of heat transmission competence. The heat transfer rate is increased by 21.87 % for the ternary hybrid nanofluid, 16.56 % for the hybrid nanofluid, and 11.25 % for the mono nanofluid when the nanoparticles volume fraction is increased from 0.01 to 0.04.</div></div>","PeriodicalId":9658,"journal":{"name":"Case Studies in Thermal Engineering","volume":"66 ","pages":"Article 105460"},"PeriodicalIF":6.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143322287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}