International Journal of Heat and Mass Transfer最新文献

{"title":"Particle sedimentation in cored-wire-arc directed energy deposition: Particle migration and suppression mechanism via ultrasonic vibration","authors":"Junwei Yang ,&nbsp;Hao Yi ,&nbsp;Le Jia ,&nbsp;Zhixu Dong ,&nbsp;Huajun Cao","doi":"10.1016/j.ijheatmasstransfer.2024.126446","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126446","url":null,"abstract":"<div><div>Cored-wire-arc directed energy deposition (DED), as an emerging manufacturing technology, can achieve multi-material additive manufacturing and satisfy the demand for structural-functional integration. However, high-density particles will sink and aggregate at the bottom of molten pool, which will cause defects such as cracks or porosity, decreasing the bonding between the deposited layers and deteriorating the mechanical properties of the components. Therefore, it is essential to investigate the migration behavior of particles in molten pool and the suppression strategy to improve formation quality. Here, a three-dimensional numerical model is developed to reveal the molten pool dynamics and particles migration mechanism during cored-wire-arc DED. The influence of molten droplets impingement and molten pool flow on particles migration behavior in the additive manufacturing process is investigated. Furthermore, the effect regulation of relative velocity between particle and molten pool on particles migration behavior is analyzed mechanistically, which reveals the sedimentation mechanism of the particles. Results demonstrate that molten pool flow velocity will influence the relative velocity between particles and molten pool, which will decide the acceleration of particles; moreover, the particles will sink while the relative velocity is in the same direction with gravity or the relative velocity is lower. Finally, ultrasonic vibration (UV) is introduced to suppress the sedimentation and aggregation of particles, and the corresponding suppression mechanism is revealed. UV will increase the flow velocity of molten pool, which will suppress the sedimentation and agglomeration of particles, as well as reduce the temperature gradient of molten pool, increasing the depth of penetration. This work provides a foundation for further improving the quality of components fabricated via cored-wire-arc DED.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126446"},"PeriodicalIF":5.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651058","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 effects of rolling and heaving on flow boiling heat transfer in a 3 × 3 rod bundle channel in a natural circulation system","authors":"Jing-Liang Bi,&nbsp;Feng Xie,&nbsp;Yan-Ping Huang,&nbsp;Wei Bao,&nbsp;Jian-Jun Xu,&nbsp;Dian-Chuan Xing","doi":"10.1016/j.ijheatmasstransfer.2024.126428","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126428","url":null,"abstract":"<div><div>Floating nuclear power plants are always influenced by sea waves. Rolling and heaving are two common conditions the plants will be subjected to. The previous rod bundle flow boiling experiments are mostly conducted at low pressure, and the results cannot be directly utilized in the nuclear power plants. Flow boiling experiments at 13–13.5 MPa and visualization experiments in a 3 × 3 rod bundle channel for rolling and heaving conditions were conducted in this research. The effects of rolling and heaving on flow boiling heat transfer coefficients (HTCs) and bubble dynamics in the rod bundle were analyzed for both subcooled and saturated boiling. The visualization results reveal that when the rolling angle is large, the void fraction of the fluid is much larger than that in the vertical static channel for most of the rolling period, and in a heaving period, the void fraction is larger than that in the static vertical channel for half the period. The experimental results show that the fluctuation amplitude of HTCs will become larger when rolling amplitude increases. When the maximum rolling angle is 10°, the average HTC during rolling process is the same with the HTC in the static vertical channel. Only when the rolling angle is 30°, the average HTC during the whole rolling process is 6.15 % higher than the static HTC. In the heaving process, the mass flux and flow boiling HTCs vary in a sine plot with the periodical movement. When the heaving amplitude becomes larger or heaving period becomes shorter, the additional driving force will increase and the mass flux fluctuation amplitude and HTC fluctuation amplitude become larger. Heaving has little effect on the time-averaged flow boiling HTCs in the rod bundle. This research widens the experimental data of high pressure flow boiling for motion conditions, and the results can be useful to the design of floating nuclear power plants.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126428"},"PeriodicalIF":5.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651843","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":"Gas slip flow and heat transfer over a semi-confined cylinder in proximity to a solid wall","authors":"Wei Dai,&nbsp;Huiying Wu,&nbsp;Zhenyu Liu","doi":"10.1016/j.ijheatmasstransfer.2024.126439","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126439","url":null,"abstract":"<div><div>A numerical simulation with second-order velocity slip and temperature jump models has been conducted to investigate gas slip flow and heat transfer over a semi-confined cylinder in proximity to a solid wall. The effects of rarefaction (characterized by <em>Kn</em>), convection (characterized by <em>Re</em>), compressibility (characterized by <em>Ma</em>), confinement (characterized by gap ratio <em>d</em>_gap<em>/d</em>_c), and temperature (characterized by cylinder-gas temperature ratio <em>T</em>_c/<em>T</em>_∞) on the drag coefficient (<em>C</em>_D) and Nusselt number (<em>Nu</em>) of a semi-confined cylinder have been comprehensively analyzed. It is found that: (1) with increasing <em>Ma</em>, the dominant effect determining the variation of <em>C</em>_D with <em>Kn</em> changes from rarefaction effect to compressibility effect, while the dominant effect determining the variation of <em>Nu</em> with <em>Kn</em> changes from temperature jump to velocity slip; (2) with increasing <em>Ma</em>, the variation of <em>C</em>_D with increasing <em>Re</em> changes from a monotonic decrease to a non-monotonic variation owing to the compressibility effect, while <em>Nu</em> increases monotonically with increasing <em>Re</em> owing to an enhanced convection effect; (3) with decreasing <em>d</em>_gap<em>/d</em>_c, <em>C</em>_D first increases, then decreases owing to the variation of gas velocity gradient and pressure surrounding the cylinder, while <em>Nu</em> first increases, then decreases, finally increases again owing to the variation of gas velocity and temperature gradient surrounding the cylinder; (4) with increasing <em>T</em>_c/<em>T</em>_∞, <em>C</em>_D and <em>Nu</em> increase owing to increases of gas dynamic viscosity and pressure, thermal conductivity and temperature gradient, respectively. Finally, dimensionless correlations for <em>C</em>_D and <em>Nu</em> of a semi-confined cylinder with comprehensive considerations of rarefaction, convection, compressibility, confinement, and temperature effects are proposed.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126439"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651059","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 thermal conductivity of photopolymerizable rubbery and glassy thiol-ene composites filled with hexagonal boron nitride","authors":"Moustafa M. Zagho ,&nbsp;Jesse C. Jenkins ,&nbsp;Dana M. Pinson ,&nbsp;Travis L. Thornell ,&nbsp;Sarah E. Morgan ,&nbsp;Derek L. Patton ,&nbsp;Sergei Nazarenko","doi":"10.1016/j.ijheatmasstransfer.2024.126431","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126431","url":null,"abstract":"<div><div>In this study, a facile and speedy method of making highly thermally conductive polymer composites containing hexagonal boron nitride (h-BN) was demonstrated. Rubbery and glassy at room temperature thiol-ene based composites were fabricated by mechanical mixing of unmodified h-BN microparticles with different liquid thiol and ene monomers followed by UV-curing of the cast films. Thermal diffusivity of the composites was directly measured by a Light Flash Analyzer (LFA) while thermal conductivity calculated from thermal diffusivity, density, and thermal capacity at constant pressure. Scanning electron microscopy (SEM) was used to investigate the morphology of the composites, in particular, the particle orientation and spatial arrangement. Both rubbery and glassy thiol-ene based composites exhibited very high levels of thermal conductivity for the composites prepared via mechanical mixing. For instance, the thermal conductivity of the rubbery and glassy composites with 40 wt% of h-BN were 1.38 W/m·K and 0.74 W/m·K as compared to 0.19 W/m·K and 0.11 W/m·K for the unfilled networks, respectively. The thermal conductivity versus h-BN content experimental data were fit to the Nielsen model which showed a good agreement. But the only fitting parameter of the model, which is related to the particle aspect ratio, turned out to be greater than the calculated one based on the real dimensions of h-BN filler. The SEM data have shed light on this behavior. The h-BN phase was uniformly dispersed and mainly made of tiny aggregates in which the stacked platelets demonstrated one way sliding, like steps in a staircase, thus forming quasiparticles with an increased aspect ratio. The study also revealed the effect of h-BN particle size and processing conditions such as adding a small amount of solvent used to reduce viscosity of the thiol/ene/h-BN mixture prior to photopolymerization on the thermal conductivity of the composites.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126431"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651886","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":"Reynolds-averaged Navier-Stokes simulations of opposing flow turbulent mixed convection heat transfer in a vertical tube","authors":"Kosuke Motegi ,&nbsp;Yasuteru Sibamoto ,&nbsp;Takashi Hibiki","doi":"10.1016/j.ijheatmasstransfer.2024.126406","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126406","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This study performed Reynolds-Averaged Navier-Stokes (RANS) simulations of a single-phase turbulent opposing flow mixed convection in a heated vertical circular tube. Previous research has reported that the Launder-Sharma &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mrow&gt;&lt;mi&gt;ε&lt;/mi&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; model (hereafter the LS model), one of the most popular RANS turbulence models, sometimes overestimates experimental data of heat transfer coefficients for opposing flows. Although the RANS models have been widely applied to opposing flows in various engineering problems, the conditions under which the anomaly in the LS model occurs and the underlying mechanisms remain unclear. This study aimed to understand the model characteristics and their applicability under various mixed convection conditions. This study investigated the LS model, the LS model with the Yap correction, and the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msup&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; model, comparing them with existing experimental data of the Nusselt number and the friction coefficient in fully developed regions. The LS model remarkably over-predicted the Nusselt number and the friction coefficient under highly buoyant conditions. The error for the Nusselt number was &gt;90 % for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;J&lt;/mi&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;≈&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;J&lt;/mi&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; is a controlling parameter characterizing the strength of buoyancy influence. The conditions under which the prediction of the LS model failed were linked to those under which reverse flow occurred near the heated wall. We obtained &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;J&lt;/mi&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;≈&lt;/mo&gt;&lt;mn&gt;1.25&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; for the reverse flow condition. This condition could be used where the LS model could not be applied. The LS model with Yap correction and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msup&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; model could predict experimental data successfully from forced convection to mixed convection conditions &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;J&lt;/mi&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. For natural convection-dominant conditions &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;J&lt;/mi&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;msup&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, the LS model with the Yap correction was numerically unstable and could not ob","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126406"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651057","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":"Ingress wave model with purge-mainstream density ratio","authors":"Hui Tang,&nbsp;Simon Vella,&nbsp;Carl M. Sangan,&nbsp;James A. Scobie,&nbsp;Gary D. Lock","doi":"10.1016/j.ijheatmasstransfer.2024.126372","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126372","url":null,"abstract":"<div><div>Aeroengines operate with a cooling flow (purge) at a significant purge-mainstream density ratio (DR), which is principally created by the differences in temperatures of these two streams. This paper will show there is a profound influence of DR on ingress, purge flow rates, and sealing effectiveness - all crucial to the superordinate aim of achieving a high thermodynamic efficiency for the engine. A new theoretical (low-order) model is introduced to enable the engine designer to flexibly predict the required purge to prevent ingress over a range of typical operating conditions. The Ingress Wave Model is based on the physical principle that unsteadiness, in the form of large-scale rotating instabilities, forms a circumferential pressure gradient driving fluidic motion against the Coriolis force. The shear created by the difference in tangential momentum between adjacent flow streams is assumed to be the primary mechanism in the process. This allows a set of equations to be derived from dimensional analysis and the assumption that flow entrainment is a function of the relative egress momentum and ingress density. The model is validated against data collected at both DR = 1 and 1.52, with good quantitative agreement across a range of purge and annulus flow conditions. Typical engine design practice exploits information captured in experimental rigs operating in benign conditions at low technology readiness level (TRL) and DR = 1. The new model is used to scale such data collected from six experimental facilities to the density ratios expected in current state-of-the-art (DR = 1.5) and future (DR = 2) engines. The result is a requirement for significantly reduced purge, with profound practical implications for the engine designer, in particular for future engines which operate at higher purge-mainstream density ratios.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126372"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651100","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":"Void fraction covariance and relative velocity covariance for steam-water boiling flows in NUPEC Type I and Type II rod bundles","authors":"Hengwei Zhang ,&nbsp;Tetsuhiro Ozaki ,&nbsp;Takashi Hibiki","doi":"10.1016/j.ijheatmasstransfer.2024.126435","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126435","url":null,"abstract":"<div><div>Accurately modeling gas-liquid two-phase flows in rod bundles is critical for process engineering, equipment optimization, and safety assessments involving rod bundle channels. Void fraction covariance and relative velocity covariance are key parameters that indicate the effect of non-uniform void fraction distribution on the value of area-averaged relative velocity. Reliable correlations for these covariances are essential for accurately modeling two-phase flows in system analysis codes. Developing constitutive relations for void fraction and relative velocity covariance requires accurate experimental data. Under light water-cooled reactor conditions, X-ray computed tomography (CT) is suitable for measuring gas-liquid two-phase flows. However, measurement noise is often present in the void fraction distribution data collected by X-ray CT. To address this, a post-processing algorithm was developed to remove noise from the X-ray CT data for rod bundle channels under BWR prototypical conditions. Based on the optimized data, constitutive correlations for void fraction covariance and relative velocity covariance in rod bundles were established for both bulk and subcooled boiling flows. The mean absolute relative deviations of these correlations for void fraction covariance and relative velocity covariance were 1.03 % and 0.956 %, respectively. Furthermore, the developed correlation was validated for a rod bundle containing a large water rod, with mean absolute relative deviations of 0.851 % for void fraction covariance and 1.31 % for relative velocity covariance.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126435"},"PeriodicalIF":5.0,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651110","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 and molecular dynamics simulation study of the thermal conductivity mechanism of biolubricant-based functionalized silver/carbon black additives","authors":"Weiwei Guan ,&nbsp;Xianjun Hou ,&nbsp;Hua Jiang ,&nbsp;Youheng Wang ,&nbsp;Mohamed Kamal Ahmed Ali","doi":"10.1016/j.ijheatmasstransfer.2024.126412","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126412","url":null,"abstract":"<div><div>Lubricant degradation under elevated temperatures is a critical challenge in the automobile and manufacturing sectors, which reduces the durability of machinery components. In this study, a new environmentally friendly castor oil-based lubricant was developed utilizing tert‑butylhydroquinone (TBHQ)-functionalized silver/carbon black (Ag/CB@TBHQ) nano-additives. Herein, the mechanism of thermal conductivity improvement in Ag/CB@TBHQ nanolubricant was investigated by experimental tests and molecular dynamics simulations. Furthermore, the hybrid Ag/CB@TBHQ nano-additive presented superior thermal conductivity compared to individual nano-additives (Ag or CB) under various concentrations and temperatures. Additionally, the study presented the improved tribological performance of a novel nanolubricant under various temperatures. In summary, our results will offer promising insights to enhance the heat transfer capability and tribological performance of mechanical systems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126412"},"PeriodicalIF":5.0,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651099","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 study on a LTO cell module: Experiment, 3D numerical analysis and model order reduction","authors":"Nicolò Zatta ,&nbsp;Giovanni Bonanno ,&nbsp;Andrea Trovò ,&nbsp;Giovanni Cristofoli ,&nbsp;Paolo Mattavelli ,&nbsp;Massimo Guarnieri","doi":"10.1016/j.ijheatmasstransfer.2024.126407","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126407","url":null,"abstract":"<div><div>Understanding and controlling the temperature evolution of Lithium-ion batteries is crucial to maintain high performance, ensuring long cycling life and avoiding thermal abuse. This paper presents a numerical and experimental thermal analysis of an air-cooled industrial module provided with 20 prismatic lithium-titanate-oxide cells. First, a 3D numerical model is presented for studying the dynamic distribution of the module temperature when the cooling fans are turned on or off. The numerical results are validated against test bench measurements. The flow field investigation explains the uneven temperature distribution among cells. The computation in natural convection inside the module, i.e. with fans off, was resolved by means of a fine empirical tuning. Building on the results of the 3D model, a 0D lumped model has been developed resorting to a model order reduction (MOR) technique and an energy balance differential equation. The model was characterized by tuning the module experimental data coming from a straight-forward testing protocol. The 0D MOR model, implemented on Simulink, demonstrated capable of quickly predicting the highest cell temperatures, allowing an easy and precise control of the module temperature, with an error <span><math><mo>&lt;</mo></math></span> 1<!--> <!-->°C.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126407"},"PeriodicalIF":5.0,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651092","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 peridynamic model for oxidation and damage in zirconium carbide ceramics","authors":"Francesco Scabbia ,&nbsp;Claudia Gasparrini ,&nbsp;Mirco Zaccariotto ,&nbsp;Ugo Galvanetto ,&nbsp;Florin Bobaru","doi":"10.1016/j.ijheatmasstransfer.2024.126414","DOIUrl":"10.1016/j.ijheatmasstransfer.2024.126414","url":null,"abstract":"<div><div>Zirconium carbide (ZrC) has potential to be applied in next-generation nuclear reactors for space missions and industrial applications. The mechanisms controlling ZrC oxidation dependence on temperature, material composition, pressure, porosity are not fully understood. In this work, we use a peridynamic modeling of diffusion/reaction across several regions observed in previous experiments to explain the oxygen diffusion mechanism and reaction kinetics. We emphasize the importance in the oxidation and damage process of a transition layer of partially-oxidized ZrC. The peridynamic model has an autonomously moving oxidation interface, and the delamination/detachment of oxide (induced by large volumetric expansion) is simulated here with an oxygen concentration-driven damage model. Once the diffusion properties are calibrated to match the measured oxygen concentration across the oxidation front, the speed of propagation of the oxidation front is predicted by a 1D peridynamic model in excellent agreement with experimental observations. An extension to 2D finds the shape of remaining unoxidized ZrC conforming to experimental observations.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"237 ","pages":"Article 126414"},"PeriodicalIF":5.0,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651093","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}