International Journal of Thermal Sciences最新文献

{"title":"Experimental study on endwall film cooling performance of an adjustable guide vane","authors":"Yifei Yan ,&nbsp;Liming Song ,&nbsp;Yunjia Yao ,&nbsp;Zhi Tao ,&nbsp;Jun Li","doi":"10.1016/j.ijthermalsci.2024.109440","DOIUrl":"10.1016/j.ijthermalsci.2024.109440","url":null,"abstract":"<div><div>Variable-geometry turbines are a crucial technology in advanced variable cycle engines, with the inevitable endwall clearance caused by blade rotation being a key concern. While current research primarily focuses on its influence on aerodynamics performance, there is a notable dearth of studies on endwall cooling behaviors. To this end, this article establishes an experimental platform to assess the endwall film cooling characteristics of adjustable guide vanes. Firstly, the film cooling characteristics were compared between traditional fixed guide vanes and adjustable guide vanes with a 0° turning angle under different MFRs (0.5 %, 1.0 %, 1.5 %). Results demonstrate that the adjustable guide vane configuration expands the film coverage on the endwall near the leading and trailing edges under the MFR investigated. This is because the leakage flow caused by clearances transports some coolant into these gaps, effectively suppressing them on the endwall surface, thereby creating a beneficial cooling coverage effect. Subsequently, the influence of turning angles (0°, −1.5°, −3°) on the film cooling characteristics of adjustable guide vanes was further investigated. Results indicate that turning angle exerts minor influences on cooling effectiveness near the LE clearance. However, a slight enhancement in cooling effectiveness near the TE clearance is observed with decreasing turning angles.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109440"},"PeriodicalIF":4.9,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358518","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":"Lean premixed combustion and thermal performances of a burner with a heat-conducting perforated plate","authors":"Lang Li ,&nbsp;Kai Tan ,&nbsp;Xiaojun Xiong ,&nbsp;Feixiang Li ,&nbsp;Jianlong Wan","doi":"10.1016/j.ijthermalsci.2024.109453","DOIUrl":"10.1016/j.ijthermalsci.2024.109453","url":null,"abstract":"<div><div>To improve the lean premixed combustion LPC stabilization, a burner with a rectangular perforated plate is proposed, and the LPC features of methane-air in this burner are investigated via experiment and simulation. The result demonstrates that the lean premixed flame LPF can remain stable until it blows off. Subsequently, the flame behavior and structure are analyzed quantitatively. When the equivalence ratio increases, the flame height and thickness decrease. Then, the jet-flame anchoring mechanism is revealed. When the equivalence ratio decreases, the decreased positive effect of heat recirculation reduces the anchoring performance of the flame tip, but the decreased negative effect of heat-loss contributes to anchoring the flame root. The preferential transport effect primarily contributes to the anchoring performance of flame root rather than that of the flame tip. Such detailed visualization of the aforementioned main factors on the lean premixed jet-flame stabilized on the perforated plate has not been reported. This work helps us understand the lean premixed jet-flame dynamics stabilized on the perforated plate further.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109453"},"PeriodicalIF":4.9,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421560","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":"Thin-film evaporation in microchannels: A combined analytical and computational fluid dynamics approach to assessing meniscus curvature impact","authors":"Ali Mostafazade Abolmaali,&nbsp;Mohamad Bayat,&nbsp;Jesper Hattel","doi":"10.1016/j.ijthermalsci.2024.109455","DOIUrl":"10.1016/j.ijthermalsci.2024.109455","url":null,"abstract":"<div><div>Computational fluid dynamics (CFD) is employed to investigate the effects of variation in bulk meniscus curvature on evaporative heat and mass transfer in microchannels. Evaporation in microchannels presents a classic multiscale problem, encompassing both microscopic and macroscopic length scales in the thin-film and bulk meniscus regions, respectively. Therefore, the liquid-vapor interface or meniscus shape is first determined through thin-film evaporation analysis using numerical approaches found in the literature. However, a new approach for establishing boundary conditions is also proposed, allowing for the representation of varying curvatures within the bulk meniscus region. Then, the obtained meniscus thickness profiles are exported to a two-dimensional CFD framework. The primary advantage of this developed CFD framework lies in its capability to simultaneously analyze evaporative heat and mass transfer from both microscopic and macroscopic regions, a feature that enhances research endeavors concerning micro and miniature heat pipes. The developed model is applied to various rectangular microchannel sizes, ranging from 10 to 100 μm in width, with wall superheats varying from 0.1 to 3.0 K. The aim is to quantify the effects of variations in bulk meniscus curvature on the evaporative characteristics of the extended meniscus (comprising both thin-film and bulk meniscus regions), using the concept of thermal resistance. Consequently, based on the CFD simulation results, multiple regression analysis is employed to formulate the total thermal resistance in terms of independent parameters, namely the microchannel width, wall superheat, and the radius of curvature (<em>R</em>_<em>c</em>). It is observed that the radius of curvature has a marginal impact on the total thermal resistance, allowing its influence to be expressed by a power-law function of (<em>R</em>_<em>c</em>/<em>R</em>_<em>m</em>)^0.102, where <em>R</em>_<em>m</em> represents the minimum radius of curvature.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109455"},"PeriodicalIF":4.9,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358519","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":"Exact momentum layer and thermal field solutions for the fluid flow due to a moving/deforming Riga plate","authors":"Mustafa Turkyilmazoglu","doi":"10.1016/j.ijthermalsci.2024.109448","DOIUrl":"10.1016/j.ijthermalsci.2024.109448","url":null,"abstract":"<div><div>One of the most ingenious ways to control the flow and its dynamics in boundary layers is the use of an electromagnetic actuator setup called a Riga plate. Through the interaction of electric and magnetic forces, stabilized flow motion can be achieved over the Riga plate. The stringent control provided by the electro-magnetohydrodynamic Lorentz force, acting either with or against the flow direction, has attracted researchers worldwide to explore the further impacts of physical mechanisms on the Riga plate, both in its stationary state and when moving with the flow. However, the high nonlinearity of the governing equations necessitates numerical simulations for the latter configuration. This often leads to scholars neglecting the magnetization of the permanent magnets, which essentially renders the actuator inactive, while code validation. To avoid this unrealistic scenario in future studies involving the Riga plate, it is essential to find easily accessible analytical solutions, even if their range of validity is limited. Therefore, this research paper presents exact fluid flow solutions and series heat solutions in terms of exponentially decaying functions. These simple solutions for the flow, temperature, drag, and heat transfer over moving or extendable Riga plates, in the presence of an active actuator, will help us understand the impacts of physical mechanisms and validate the accuracy of numerical techniques in future applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109448"},"PeriodicalIF":4.9,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358515","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":"Flame instability and heat transfer effect during deflagration of premixed hydrogen in tunnel","authors":"BaiWei Lei ,&nbsp;Zekai Guo ,&nbsp;Chaoyu Song ,&nbsp;Changna Guo","doi":"10.1016/j.ijthermalsci.2024.109452","DOIUrl":"10.1016/j.ijthermalsci.2024.109452","url":null,"abstract":"<div><div>In the process of hydrogen deflagration, thermal diffusion and fluid dynamics instability lead to the instability of premixed flames. With the enhancement of instability, the behavior of the flame front becomes unstable, leading to an increase in flame surface area and flame speed. This study used the three-dimensional full-speed CFD code GASFLOW-MPI to perform numerical simulations of tunnel model deflagration experiments based on the compressible Navier-Stokes equations. The turbulent combustion model used in the study takes into account the effects of thermal diffusion instability, fluid dynamics instability, and local turbulent disturbances. This paper quantitatively calculates the thermal diffusion and fluid dynamics instability to explore their effects on developing tunnel premixed hydrogen deflagration flames. Based on the effective Lewis number of the unburned premixed gas of the flame front and the ratio of thermal expansion to the flame thickness, the interaction behavior between them is analyzed. Additionally, this paper explores in depth the influence of heat transfer boundary conditions on the propagation of flame instability. Results show that the calculation results of the combustion model considering heat transfer effects are highly consistent with the experimental values, demonstrating the importance of heat loss in the overpressure peak and pressure decay process. During the deflagration process, thermal radiation plays a leading role, while heat convection makes the main contribution to heat loss during pressure decay. As the flame evolves, the destabilizing effect of fluid dynamics instability first increases and then decreases, while the stabilizing effect of thermal diffusion instability gradually weakens and transitions to a destabilizing effect, with both effects mutually reinforcing each other. Heat transfer effects delay mixing hydrogen-premixed gases with fresh air, slowing the transition of thermal diffusion instability from stability to instability, weakening the destabilizing effect of fluid dynamics instability, and thereby delaying the evolution process from competition to promotion between the two.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109452"},"PeriodicalIF":4.9,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358516","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":"The effective thermal conductivity of micro/nanofilm under different heating conditions using nongray Boltzmann transport equation","authors":"Ru Jia ,&nbsp;Yufei Sheng ,&nbsp;Jiaxuan Xu ,&nbsp;Han Xie ,&nbsp;Hua Bao","doi":"10.1016/j.ijthermalsci.2024.109446","DOIUrl":"10.1016/j.ijthermalsci.2024.109446","url":null,"abstract":"<div><div>It is known that Fourier's law breaks down at micro/nanoscale and that the classical definition of thermal conductivity from this law becomes invalid. Therefore, adopting a size-dependent effective thermal conductivity for micro and nanofilm is a prevalent strategy to describe the heat transfer at micro/nanoscale. Most of the existing discussion focuses on the size effect of effective thermal conductivity, while the dependence of thermal conductivity on heating conditions is less explored. In this work, we employed the nongray phonon Boltzmann transport equation to obtain the effective thermal conductivity of micro/nanofilm under three typical heating conditions, including temperature difference, internal heat source, and transient thermal grating. It is found that for all three heating conditions, the effective thermal conductivity increases with characteristic length and converges to the bulk value. Nevertheless, the effective thermal conductivities in the three heating conditions are different. For the same characteristic length, the effective thermal conductivity extracted with the temperature difference is larger than transient thermal grating, and both are larger than that with the internal heat source. Such a conclusion is further consolidated by the calculation results for a few different semiconductor materials with diverse mean free path distributions. Furthermore, we proposed a convenient semi-analytical approach to accurately predict effective thermal conductivity under different heating conditions for micro/nanofilms.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109446"},"PeriodicalIF":4.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358514","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 radiative heat transfer and modulation using VO2-based metasurfaces","authors":"Bowei Xie ,&nbsp;Deyu Xu ,&nbsp;Shangyu Zhang ,&nbsp;Junming Zhao ,&nbsp;Linhua Liu","doi":"10.1016/j.ijthermalsci.2024.109442","DOIUrl":"10.1016/j.ijthermalsci.2024.109442","url":null,"abstract":"<div><div>Thermal modulators based on phase change materials have gained attention due to their ability to self-adaptively tune the heat flux. However, achieving a large positive modulation ratio with increasing temperature remains challenge. In this work, we present a near-field thermal modulator with a large modulation ratio and heat transfer coefficient. The thermal modulator consists of two identical VO₂ metasurfaces placed on planar Au substrates. The thermal modulator can achieve three stages, corresponding to three different combinations of phase states of VO₂. An extremely large heat transfer coefficient with value exceeds 20000 W/m² K is achieved at a room temperature of 300 K, and the largest modulation ratio is about 12. The underlying mechanism involved in the modulator is the construction of cavity surface plasmon polaritons for the metallic state and the suppression of surface phonon polaritons for the dielectric state. Meanwhile, we numerically demonstrate the excellent modulation performance of the proposed modulator as a contact filling in the spacecraft applications. This work can accelerate the utilization of near-field thermal modulators in thermal management and thermal circuit applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109442"},"PeriodicalIF":4.9,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326744","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":"Numerical modeling of heat transfer mechanism in remote sensing bulb of thermal expansion valves","authors":"Saima Alam,&nbsp;Blake Gower,&nbsp;Norbert Mueller","doi":"10.1016/j.ijthermalsci.2024.109438","DOIUrl":"10.1016/j.ijthermalsci.2024.109438","url":null,"abstract":"<div><div>Thermal management of automotive systems has garnered a lot of focus in recent times to improve the energy efficiency of vehicles and address the challenge of global warming. In combustible fuel vehicles, the heat pump compressor is driven by the engine power which leads to changes in operating condition of the cycle while the vehicle is in motion. In electric vehicles, a combined thermal management strategy handles both cabin and battery pack cooling/heating depending on the ambient conditions and power requirements by adjusting refrigerant flow rates and flow directions with sophisticated valves. Irrespective of the vehicle type, effective variable refrigerant flow control is prerequisite to ensure optimum thermal comfort with minimum energy. Thermal expansion valves (TXV) are the most widely used method for regulating mass flow rate of refrigerant during the expansion step of the vapor compression cycle based on the principle of trying to maintain a fixed degree of superheat at the evaporator outlet. Conventional models of the thermal expansion valve ignore the time lag between fluctuation of temperature at the evaporator outlet and the corresponding change in pressure of the TXV remote sensing bulb, treating the valve as an instantaneous element during transient operation. This paper presents a novel method for determining the temperature profile and time constant of the remote sensing bulb response using numerical methods, in an attempt to capture the dynamics of thermal expansion valve in active heat pump cycle. Finite difference method was used to solve for the conduction heat transfer between the bulb and the heat exchanger outlet tube in perfect thermal contact applying the necessary boundary conditions. This improved modeling approach will be helpful in better prediction of the dynamic behavior of thermal expansion valves and how it influences the evaporative heat exchanger performance during transient operations to determine control algorithm and strategies.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109438"},"PeriodicalIF":4.9,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326741","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":"Application of a thermal circuit model for the prediction of interfacial thermal resistance between water and a nanostructure surface using molecular dynamics simulations","authors":"Zhiwen Jiang,&nbsp;Masahiko Shibahara","doi":"10.1016/j.ijthermalsci.2024.109441","DOIUrl":"10.1016/j.ijthermalsci.2024.109441","url":null,"abstract":"<div><div>The present study proposes various thermal circuit models (TCMs) to predict interfacial thermal resistances (ITRs) between water and a nanostructure surface. The effects of water models, nanopillar widths on nanostructure surfaces, and composite surfaces on the relationship between ITRs calculated by non-equilibrium molecular dynamics simulations and ITRs predicted by TCMs are investigated in water-copper and water-graphene-copper systems. The results reveal that the ITRs predicted by some TCMs are slightly affected by water pressure, while MD-calculated ITRs of the nanostructure surfaces in the Wenzel states agree with most of the predicted ITRs. Additionally, it is demonstrated that water molecules in the groove of a nanostructure surface play a crucial role in TCMs in the Cassie-Baxter states. Considering the effective contact region of water molecules in the groove in the Cassie-Baxter states, the use of TCMs can effectively reduce the prediction error of ITRs.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109441"},"PeriodicalIF":4.9,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326742","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":"Bubble characterization and bubble population on SiC material surface in subcooled boiling flow","authors":"Bing Tan ,&nbsp;Jiejin Cai ,&nbsp;Songbai Cheng","doi":"10.1016/j.ijthermalsci.2024.109447","DOIUrl":"10.1016/j.ijthermalsci.2024.109447","url":null,"abstract":"<div><div>A particularly promising candidate for widespread adopted Accident-Tolerant Fuels(ATF) is Silicon Carbide (SiC), which is deemed significantly advantageous for nuclear energy applications due to its remarkable characteristics. The understanding of bubble behavior on SiC surfaces is critical for the development of improved SiC designs. An experiment study was executed to evaluate the characteristics and population of bubbles on the surface of SiC material in subcooled boiling flow. The experimental setup maintained atmospheric pressure and featured a subcooling range of 0–12 K and a wall superheat from 0K to 30K, and a maximum coolant Reynolds number of 10400. The findings accentuated that the sensitivity of heat to fluid velocity during nucleation boiling is greater on surfaces with small porosity than on those with larger porosity. The Sauter mean diameter displays an upward trend in sync with increasing wall superheat, and the Sauter mean diameter can be represented as a dependence of the maximum and minimum bubble diameters. In terms of bubble distribution properties, it was discovered that bubble size and bubble aspect ratio conform to a lognormal distribution, while bubble orientation adheres to a normal distribution, and bubble circularity validates a Weibull distribution.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"208 ","pages":"Article 109447"},"PeriodicalIF":4.9,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326743","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}