Pub Date : 2025-02-07DOI: 10.1016/j.ijheatmasstransfer.2025.126767
Jing Dong , Lu Zhang , Ke-Qing Xia
We report a quantitative shadowgraphy for measuring both the vertical and horizontal Nusselt numbers ( and ) in turbulent thermal convection. An exact relationship between and the shadowgraph intensity (and a similar one for ) is derived for the first time. We use a quasi-two-dimensional Rayleigh–Bénard convection cell where an effective horizontal buoyancy is introduced by tilting as a test platform to validate the method. In addition, we conduct complementary direct numerical simulations to confirm the validity of this new method. With increasing horizontal to vertical buoyancy ratio, the measured vertical Nusselt number shows a non-monotonic behavior, whereas the horizontal Nusselt number first increases from approximately zero and then saturates to a value being an order of magnitude smaller than . A detailed analysis of the transport properties and flow fields identifies a plume-controlled regime, a transitional regime, and a shear-dominated regime for the present system.
{"title":"Quantitative shadowgraphy for heat transport measurement in turbulent thermal convection","authors":"Jing Dong , Lu Zhang , Ke-Qing Xia","doi":"10.1016/j.ijheatmasstransfer.2025.126767","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126767","url":null,"abstract":"<div><div>We report a quantitative shadowgraphy for measuring both the vertical and horizontal Nusselt numbers (<span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi></mrow><mrow><mi>V</mi></mrow></msub></mrow></math></span> and <span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi></mrow><mrow><mi>H</mi></mrow></msub></mrow></math></span>) in turbulent thermal convection. An exact relationship between <span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi></mrow><mrow><mi>V</mi></mrow></msub></mrow></math></span> and the shadowgraph intensity (and a similar one for <span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi></mrow><mrow><mi>H</mi></mrow></msub></mrow></math></span>) is derived for the first time. We use a quasi-two-dimensional Rayleigh–Bénard convection cell where an effective horizontal buoyancy is introduced by tilting as a test platform to validate the method. In addition, we conduct complementary direct numerical simulations to confirm the validity of this new method. With increasing horizontal to vertical buoyancy ratio, the measured vertical Nusselt number shows a non-monotonic behavior, whereas the horizontal Nusselt number first increases from approximately zero and then saturates to a value being an order of magnitude smaller than <span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi></mrow><mrow><mi>V</mi></mrow></msub></mrow></math></span>. A detailed analysis of the transport properties and flow fields identifies a plume-controlled regime, a transitional regime, and a shear-dominated regime for the present system.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143354544","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}
Mechanical motion is unavoidably accompanied by vibration, which has an effect on fluid heat transfer. However, few investigations have been conducted on the effects of vibration on heat transfer characteristics of supercritical CO2 (SCO2). In this paper, effects of transverse vibration on heat transfer characteristics of SCO2 during upward flow in a vertical tube (d = 4.57 mm, 20379≤Re≤88285) are studied experimentally. The results show that vibration achieves heat transfer enhancement. Specifically, with the increase of vibration amplitude and vibration frequency, the wall temperature decreases, the heat transfer coefficient increases, and the heat transfer enhancement efficiency (HTE) shows an upward trend. HTE of amplitude outweighs that of frequency over the test range, with an HTE of up to 32.70%. Heat transfer enhancement of vibration mainly acts in the region before mainstream enthalpy reaches pseudo-critical enthalpy. Based on pseudo-boiling theory, the reason for vibration-enhanced heat transfer is analyzed. Vibration weakens the thickness of gas-like film near the wall, thus accelerating heat transfer between the cold mainstream and the wall. A heat transfer correlation for vertical tubes under vibration is proposed based on 3822 experimental data points, which captures 94.2 % of the experimental data within ±30 % error.
{"title":"Experimental investigation of the effects of transverse vibration on the supercritical CO2 heat transfer characteristics in vertical tubes","authors":"Lin-Cheng Han, Jian Chen, Kun-Ru Wang, Qun Liu, Hua Chen, Wen-Long Cheng","doi":"10.1016/j.ijheatmasstransfer.2025.126786","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126786","url":null,"abstract":"<div><div>Mechanical motion is unavoidably accompanied by vibration, which has an effect on fluid heat transfer. However, few investigations have been conducted on the effects of vibration on heat transfer characteristics of supercritical CO<sub>2</sub> (SCO<sub>2</sub>). In this paper, effects of transverse vibration on heat transfer characteristics of SCO<sub>2</sub> during upward flow in a vertical tube (<em>d</em> = 4.57 mm, 20379≤<em>Re</em>≤88285) are studied experimentally. The results show that vibration achieves heat transfer enhancement. Specifically, with the increase of vibration amplitude and vibration frequency, the wall temperature decreases, the heat transfer coefficient increases, and the heat transfer enhancement efficiency (<em>HTE</em>) shows an upward trend. <em>HTE</em> of amplitude outweighs that of frequency over the test range, with an <em>HTE</em> of up to 32.70%. Heat transfer enhancement of vibration mainly acts in the region before mainstream enthalpy reaches pseudo-critical enthalpy. Based on pseudo-boiling theory, the reason for vibration-enhanced heat transfer is analyzed. Vibration weakens the thickness of gas-like film near the wall, thus accelerating heat transfer between the cold mainstream and the wall. A heat transfer correlation for vertical tubes under vibration is proposed based on 3822 experimental data points, which captures 94.2 % of the experimental data within ±30 % error.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126786"},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143355076","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}
Pub Date : 2025-02-07DOI: 10.1016/j.ijheatmasstransfer.2025.126766
Yitong Zheng, Zengbin Yin
Cutting temperature is one of essential signals to judge the status of cutting tool in the machining process, which is of great significance for improving the processing quality. For cutting tool temperature real-time monitoring, a method is proposed to sense the heat input of a nonlinear heat transfer system and reconstruct its temperature field. The study includes two problems: the forward and the reverse problem. For forward problems, a rapid computational model (RCM) is proposed to compute the node temperatures, which shows superiority in online applications due to the reusability of the system parameters. At each time step of the on-line process, the RCM program called the cooling and warming factor, to compute the node temperature. For inverse problems, a heat input sensing method (HISM), based on hybrid neural networks (HNNs), is developed to map temperature signals, nonlinearly, to heat inputs with an accuracy of 98%. The training data is obtained by offline finite element analysis. The coupled method, called HISM-RCM, is numerically tested in a system with nonlinear thermal properties and complex geometry with an accuracy of 99.76%. Compared with analyzed data and infrared thermography (IR), the HISM-RCM method has been shown to achieve an efficient temperature field reconstruction based on a limited number of temperature measurement points.
{"title":"Cutting temperature field online reconstruction using temporal convolution and deep learning networks","authors":"Yitong Zheng, Zengbin Yin","doi":"10.1016/j.ijheatmasstransfer.2025.126766","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126766","url":null,"abstract":"<div><div>Cutting temperature is one of essential signals to judge the status of cutting tool in the machining process, which is of great significance for improving the processing quality. For cutting tool temperature real-time monitoring, a method is proposed to sense the heat input of a nonlinear heat transfer system and reconstruct its temperature field. The study includes two problems: the forward and the reverse problem. For forward problems, a rapid computational model (RCM) is proposed to compute the node temperatures, which shows superiority in online applications due to the reusability of the system parameters. At each time step of the on-line process, the RCM program called the cooling and warming factor, to compute the node temperature. For inverse problems, a heat input sensing method (HISM), based on hybrid neural networks (HNNs), is developed to map temperature signals, nonlinearly, to heat inputs with an accuracy of 98%. The training data is obtained by offline finite element analysis. The coupled method, called HISM-RCM, is numerically tested in a system with nonlinear thermal properties and complex geometry with an accuracy of 99.76%. Compared with analyzed data and infrared thermography (IR), the HISM-RCM method has been shown to achieve an efficient temperature field reconstruction based on a limited number of temperature measurement points.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126766"},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348570","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}
Pub Date : 2025-02-07DOI: 10.1016/j.ijheatmasstransfer.2025.126789
Zhongqi Zuo , Liang Dong , Qiang Yang , Zhichao Wang , Wenyuan Zhao , Binfei Zhan , Lige Tong , Ping Wu , Li Wang
Frosting has always been a vital problem in many applications and could induce efficiency degradation or even accidents. Despite its critical role in heat and mass transport, the influence of transient airflow patterns on frosting characteristics has not been fully investigated. In this paper, the Schlieren method was combined with conventional apparatus to visually study the frosting on a horizontal cold plate under natural convection conditions. The relationship between cold surface velocity and frosting characteristics was quantitatively analyzed for variable humidities and surface temperatures. A clear reduction in horizontal velocity by more than 90 % was observed when the frost layer accumulated on the surface. Humidity and cold surface temperature showed obvious effects on airflow near the surface. The average characteristic velocities increased from 6.4 × 10−3 m/s to 8.9 × 10−3 m/s in the early frosting stage when humidity increased from 50 % to 80 % at a cold surface temperature of -9 °C. A maximum reduction in characteristic velocity of 52.6 % was observed when the cold surface temperature increased from -9 °C to -5 °C with different humidities. The natural convection influenced the heat transfer rate and the growth rate of the frost layer, particularly at the edge region of the cold plate. A criterion was proposed to identify the initial and the subsequent stages by the dimensionless number Re. When Re > 2, the frosting was in the initial stage and the heat transfer coefficient increased with humidity; when Re < 2, the frosting became stable and the heat transfer coefficient scattered around 6.58 W/m2⋅K in the present experiments.
{"title":"Visualization study of frosting characteristics on a horizontal cold plate under natural convection condition","authors":"Zhongqi Zuo , Liang Dong , Qiang Yang , Zhichao Wang , Wenyuan Zhao , Binfei Zhan , Lige Tong , Ping Wu , Li Wang","doi":"10.1016/j.ijheatmasstransfer.2025.126789","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126789","url":null,"abstract":"<div><div>Frosting has always been a vital problem in many applications and could induce efficiency degradation or even accidents. Despite its critical role in heat and mass transport, the influence of transient airflow patterns on frosting characteristics has not been fully investigated. In this paper, the Schlieren method was combined with conventional apparatus to visually study the frosting on a horizontal cold plate under natural convection conditions. The relationship between cold surface velocity and frosting characteristics was quantitatively analyzed for variable humidities and surface temperatures. A clear reduction in horizontal velocity by more than 90 % was observed when the frost layer accumulated on the surface. Humidity and cold surface temperature showed obvious effects on airflow near the surface. The average characteristic velocities increased from 6.4 × 10<sup>−3</sup> m/s to 8.9 × 10<sup>−3</sup> m/s in the early frosting stage when humidity increased from 50 % to 80 % at a cold surface temperature of -9 °C. A maximum reduction in characteristic velocity of 52.6 % was observed when the cold surface temperature increased from -9 °C to -5 °C with different humidities. The natural convection influenced the heat transfer rate and the growth rate of the frost layer, particularly at the edge region of the cold plate. A criterion was proposed to identify the initial and the subsequent stages by the dimensionless number <em>Re</em>. When <em>Re</em> > 2, the frosting was in the initial stage and the heat transfer coefficient increased with humidity; when <em>Re</em> < 2, the frosting became stable and the heat transfer coefficient scattered around 6.58 W/m<sup>2</sup>⋅K in the present experiments.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126789"},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348571","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}
Pub Date : 2025-02-07DOI: 10.1016/j.ijheatmasstransfer.2025.126757
Fatih Selimefendigil , Hakan F. Oztop
Innovative cooling strategies and efficient thermal management techniques are needed to increase the efficiency of photovoltaic (PV) modules. In the current work, a novel cooling channel method and computational approach is utilized for thermal management of PV module combined with thermoelectric generator (TEG) unit. The method uses an optimization assisted divide–combine computational approach while a trapezoidal wavy cooling channel is utilized. Hybrid nanofluid is used in the cooling channel. Simulations for cooling channel and PV-TEG unit are conducted by using finite element method while COBYLA algorithm is considered for optimization of trapezoidal wavy channel. It is shown that the corrugation amplitude has the largest effect on a trapezoidal wavy channel’s cooling effectiveness, while the inclination angle has the least effect. The range of average Nu improvements by adjusting the trapezoidal wavy channel’s amplitude, wave number, and inclination are obtained as 36%–42%, 13.5%, and 2.5%–3%. The average PV-cell temperature decreases by approximately 2.7C to 3.4C when the cooling channel is connected to the PV-TEG unit. It also decreases by approximately 1C to 1.3C when the wave number is changed. The optimum corrugation height (b/H) and inclination () for the best cooling performance are found as (b/H, )=(0.5, 36) when using 3 waves and (b/H, )=(0.5, 13.16) when using 11 waves. The PV-cell temperature drops with optimal channel configurations with wave numbers of 3 and 11 are obtained as 4.3C and 6C, respectively, in comparison to the reference cooling channel (flat channel employing only pure fluid). While the PV-TEG unit is coupled with parametric simulation of the cooling channel, generalized neural network models are used to successfully estimate the PV-cell temperature and TEG power. More complex channel assemblies and consideration of multiple PV-TEG combined units can be developed using the proposed optimization-assisted divide–combine methodology.
{"title":"Optimization assisted divide–combine approach to model cooling of a PV module equipped with TEG by using a trapezoidal shaped hybrid nano-enhanced cooling channel and performance estimation with generalized neural networks","authors":"Fatih Selimefendigil , Hakan F. Oztop","doi":"10.1016/j.ijheatmasstransfer.2025.126757","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126757","url":null,"abstract":"<div><div>Innovative cooling strategies and efficient thermal management techniques are needed to increase the efficiency of photovoltaic (PV) modules. In the current work, a novel cooling channel method and computational approach is utilized for thermal management of PV module combined with thermoelectric generator (TEG) unit. The method uses an optimization assisted divide–combine computational approach while a trapezoidal wavy cooling channel is utilized. Hybrid nanofluid is used in the cooling channel. Simulations for cooling channel and PV-TEG unit are conducted by using finite element method while COBYLA algorithm is considered for optimization of trapezoidal wavy channel. It is shown that the corrugation amplitude has the largest effect on a trapezoidal wavy channel’s cooling effectiveness, while the inclination angle has the least effect. The range of average Nu improvements by adjusting the trapezoidal wavy channel’s amplitude, wave number, and inclination are obtained as 36%–42%, 13.5<span><math><mrow><mtext>%</mtext><mo>−</mo><mn>15</mn></mrow></math></span>%, and 2.5%–3%. The average PV-cell temperature decreases by approximately 2.7<span><math><msup><mrow></mrow><mrow><mtext>o</mtext></mrow></msup></math></span>C to 3.4<span><math><msup><mrow></mrow><mrow><mtext>o</mtext></mrow></msup></math></span>C when the cooling channel is connected to the PV-TEG unit. It also decreases by approximately 1<span><math><msup><mrow></mrow><mrow><mtext>o</mtext></mrow></msup></math></span>C to 1.3<span><math><msup><mrow></mrow><mrow><mtext>o</mtext></mrow></msup></math></span>C when the wave number is changed. The optimum corrugation height (b/H) and inclination (<span><math><mi>θ</mi></math></span>) for the best cooling performance are found as (b/H, <span><math><mi>θ</mi></math></span>)=(0.5, 36) when using 3 waves and (b/H, <span><math><mi>θ</mi></math></span>)=(0.5, 13.16) when using 11 waves. The PV-cell temperature drops with optimal channel configurations with wave numbers of 3 and 11 are obtained as 4.3<span><math><msup><mrow></mrow><mrow><mtext>o</mtext></mrow></msup></math></span>C and 6<span><math><msup><mrow></mrow><mrow><mtext>o</mtext></mrow></msup></math></span>C, respectively, in comparison to the reference cooling channel (flat channel employing only pure fluid). While the PV-TEG unit is coupled with parametric simulation of the cooling channel, generalized neural network models are used to successfully estimate the PV-cell temperature and TEG power. More complex channel assemblies and consideration of multiple PV-TEG combined units can be developed using the proposed optimization-assisted divide–combine methodology.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126757"},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348604","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}
Pub Date : 2025-02-07DOI: 10.1016/j.ijheatmasstransfer.2025.126781
Haorui Zhai , Lei Zhou , Ke Lv , Shuzhou Yu , Xiaodong Li , Qingfang Huang , Tao Liu , Ying Chang , Yikun Fang , Minggang Zhu , Xiaojun Yu , Bo Li , Wei Li
The flow and heat transfer behaviors of the melt pool are very important for the obtainment of the high-quality solidified product in the melt-spinning (MS) process. In this paper, a combination method of numerical simulation and experiments is utilized to study the rapid evolution of the melt pool between the nozzle and the cooling roller during the production of Nd-Fe-B thin ribbons by using the MS process. A three-dimensional simplified model of the entire MS system is established, and a temperature-dependent UDF viscosity model of Nd-Fe-B materials is further adopted together with other thermophysical parameters to simulate the formation and evolution process of the melt pool, obtaining the thickness of the Nd-Fe-B thin ribbon. The temperature field distribution is demonstrated by simulation. The outer surface temperature of the cooling roller exhibits a "rising-falling-rising" tendency over time due to the contact with the high-temperature Nd-Fe-B alloy molten liquid and the effects of high-speed rotation and rapid cooling of the roller. The influence of temperature on the microstructure is analyzed. An obvious layered phenomenon occurs due to different flow characteristics of the Nd-Fe-B alloy molten liquid at different locations on the cooling roller caused by the varying cooling rates, which is consistent with the results observed by FE-SEM. The average relative error between the simulated and experimental values of the ribbon thickness is only 4.43 %. The effective and rapid solidification occurs on the roller-sticking surface, which makes the grains nucleate. The grain size is smaller on the roller-sticking surface. The grains grow from the roller-sticking surface to the free surface of the roller in accordance with the solidification gradient. Finally, a predictive model with the three key process factors as factors is developed to accurately predict the thickness of the Nd-Fe-B thin ribbon, with an average relative error of 4.87 %. The research results are helpful to optimize the MS process and contribute to the Nd-Fe-B thin ribbon with higher quality.
{"title":"Numerical simulation of flow and heat transfer behaviors of the melt pool in the melt-spinning process of Nd-Fe-B thin ribbons","authors":"Haorui Zhai , Lei Zhou , Ke Lv , Shuzhou Yu , Xiaodong Li , Qingfang Huang , Tao Liu , Ying Chang , Yikun Fang , Minggang Zhu , Xiaojun Yu , Bo Li , Wei Li","doi":"10.1016/j.ijheatmasstransfer.2025.126781","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126781","url":null,"abstract":"<div><div>The flow and heat transfer behaviors of the melt pool are very important for the obtainment of the high-quality solidified product in the melt-spinning (MS) process. In this paper, a combination method of numerical simulation and experiments is utilized to study the rapid evolution of the melt pool between the nozzle and the cooling roller during the production of Nd-Fe-B thin ribbons by using the MS process. A three-dimensional simplified model of the entire MS system is established, and a temperature-dependent UDF viscosity model of Nd-Fe-B materials is further adopted together with other thermophysical parameters to simulate the formation and evolution process of the melt pool, obtaining the thickness of the Nd-Fe-B thin ribbon. The temperature field distribution is demonstrated by simulation. The outer surface temperature of the cooling roller exhibits a \"rising-falling-rising\" tendency over time due to the contact with the high-temperature Nd-Fe-B alloy molten liquid and the effects of high-speed rotation and rapid cooling of the roller. The influence of temperature on the microstructure is analyzed. An obvious layered phenomenon occurs due to different flow characteristics of the Nd-Fe-B alloy molten liquid at different locations on the cooling roller caused by the varying cooling rates, which is consistent with the results observed by FE-SEM. The average relative error between the simulated and experimental values of the ribbon thickness is only 4.43 %. The effective and rapid solidification occurs on the roller-sticking surface, which makes the grains nucleate. The grain size is smaller on the roller-sticking surface. The grains grow from the roller-sticking surface to the free surface of the roller in accordance with the solidification gradient. Finally, a predictive model with the three key process factors as factors is developed to accurately predict the thickness of the Nd-Fe-B thin ribbon, with an average relative error of 4.87 %. The research results are helpful to optimize the MS process and contribute to the Nd-Fe-B thin ribbon with higher quality.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126781"},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143308758","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}
Pub Date : 2025-02-07DOI: 10.1016/j.ijheatmasstransfer.2025.126774
Jiu Yu , Wenqi Fang , Guoliang Hu , Ying Liu , Yigen Wu , Ling Peng , Yong Li
The rapid development of high-performance microelectronic devices requires high-performance ultra-thin vapor chamber (UTVC) based on phase change thermal conductivity to meet their heat dissipation requirements. Wick structure, the key component of UTVC, plays a decisive role in the heat transfer performance of UTVC. Due to the smooth surface and limited capillary force of the original wick structure, the improvement of the heat transfer performance of the UTVC was seriously restricted. In order to effectively improve the capillary performance of the wick and further improve the heat transfer performance of the UTVC, a laser ablation surface modification process was proposed in this paper. The influence of pulse energy and spacing between the adjacent pulses on the surface morphology and capillary performance of the wick structure was analyzed. The results show that laser ablation can produce rough micro-nano structures on the surface of the wick structure, which effectively improve the hydrophilicity and capillary performance of the wick structure. With the increase of pulse energy and spacing between the adjacent pulses, the capillary performance of the wick structure increases first and then decreases. The optimum process parameters of pulse energy and spacing between the adjacent pulses were 1.2 mJ and 15 μm, respectively. Compared with the original wick, the capillary rise height of spiral woven mesh and copper mesh were increased by 23.63 % and 15.38 %, respectively. In addition, the maximum heat transfer power of the UTVC without and with laser ablation (optimal parameter) was 8 W and 10.5 W, respectively.
{"title":"Effect of laser ablation surface modification on the capillary performance of the wick structure for ultra-thin vapor chamber","authors":"Jiu Yu , Wenqi Fang , Guoliang Hu , Ying Liu , Yigen Wu , Ling Peng , Yong Li","doi":"10.1016/j.ijheatmasstransfer.2025.126774","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126774","url":null,"abstract":"<div><div>The rapid development of high-performance microelectronic devices requires high-performance ultra-thin vapor chamber (UTVC) based on phase change thermal conductivity to meet their heat dissipation requirements. Wick structure, the key component of UTVC, plays a decisive role in the heat transfer performance of UTVC. Due to the smooth surface and limited capillary force of the original wick structure, the improvement of the heat transfer performance of the UTVC was seriously restricted. In order to effectively improve the capillary performance of the wick and further improve the heat transfer performance of the UTVC, a laser ablation surface modification process was proposed in this paper. The influence of pulse energy and spacing between the adjacent pulses on the surface morphology and capillary performance of the wick structure was analyzed. The results show that laser ablation can produce rough micro-nano structures on the surface of the wick structure, which effectively improve the hydrophilicity and capillary performance of the wick structure. With the increase of pulse energy and spacing between the adjacent pulses, the capillary performance of the wick structure increases first and then decreases. The optimum process parameters of pulse energy and spacing between the adjacent pulses were 1.2 mJ and 15 μm, respectively. Compared with the original wick, the capillary rise height of spiral woven mesh and copper mesh were increased by 23.63 % and 15.38 %, respectively. In addition, the maximum heat transfer power of the UTVC without and with laser ablation (optimal parameter) was 8 W and 10.5 W, respectively.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126774"},"PeriodicalIF":5.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143309126","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}
The numerical simulation of complex coupled physical interactions in high-enthalpy nonequilibrium flow poses a significant challenge in the design of Thermal Protection Systems (TPS). A new fluid-thermal-catalysis-radiation coupling scheme of conjugate heat transfer (CHT) was proposed to examine the coupling process of hypersonic flow, heat transfer, heterogeneous catalysis, and radiation interactions. Thereby, two-temperature model and Park's 5 species (O2, O, N2, N, NO) model were taken into fully coupled governing equation. In the integration within a multi-level coupling scheme, the heterogeneous catalysis model was loosely integrated, whereas the surface-to-surface radiation model was incorporated weakly. Specifically, the axisymmetric steady coupling simulation were explored over a catalysis sample holder at different heating condition. The thermodynamic non-equilibrium properties are significant, and the maximum pressure at the stagnation point behind the shock wave (2.06 kPa) is similar to the JAXA Kurotaki experiment result (2.00 kPa). The predicted stagnation heat flux for SiO2(0.294 MW/m², 0.490 MW/m², 0.731 MW/m²) at differnet heating conditions showed good agreement with the experimental data(0.319 MW/m², 0.492 MW/m², 0.720 MW/m²) reported in JAXA arc-heated wind tunnel using different catalytic coating material. In addition, the present coupling scheme further improves upon the predicted ability by comparing non-catalytic, full catalytic, and catalysis models, suggesting that more physical fields could be included if the multi level coupling relations are addressed properly.
{"title":"The investigation of fluid-thermal-catalysis-radiation coupling scheme of conjugate heat transfer for heterogeneous recombination reaction process","authors":"Wencheng Lin, Feng Hu, ZhuoChen Sui, Yuxuan Wang, Hua Jin, Yancheng You","doi":"10.1016/j.ijheatmasstransfer.2025.126753","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126753","url":null,"abstract":"<div><div>The numerical simulation of complex coupled physical interactions in high-enthalpy nonequilibrium flow poses a significant challenge in the design of Thermal Protection Systems (TPS). A new fluid-thermal-catalysis-radiation coupling scheme of conjugate heat transfer (CHT) was proposed to examine the coupling process of hypersonic flow, heat transfer, heterogeneous catalysis, and radiation interactions. Thereby, two-temperature model and Park's 5 species (O<sub>2</sub>, O, N<sub>2</sub>, N, NO) model were taken into fully coupled governing equation. In the integration within a multi-level coupling scheme, the heterogeneous catalysis model was loosely integrated, whereas the surface-to-surface radiation model was incorporated weakly. Specifically, the axisymmetric steady coupling simulation were explored over a catalysis sample holder at different heating condition. The thermodynamic non-equilibrium properties are significant, and the maximum pressure at the stagnation point behind the shock wave (2.06 kPa) is similar to the JAXA Kurotaki experiment result (2.00 kPa). The predicted stagnation heat flux for SiO<sub>2</sub>(0.294 MW/m², 0.490 MW/m², 0.731 MW/m²) at differnet heating conditions showed good agreement with the experimental data(0.319 MW/m², 0.492 MW/m², 0.720 MW/m²) reported in JAXA arc-heated wind tunnel using different catalytic coating material. In addition, the present coupling scheme further improves upon the predicted ability by comparing non-catalytic, full catalytic, and catalysis models, suggesting that more physical fields could be included if the multi level coupling relations are addressed properly.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126753"},"PeriodicalIF":5.0,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143308759","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}
This study experimentally investigated heat transfer and flow characteristics under natural convection in a closed rectangular chamber filled with HFE-7100 fluid, employing megasonic waves. Experiments using parallel heated plates with varying megasonic source distances and inter-plate spacings demonstrated a maximum heat transfer enhancement of 755 %. Particle image velocimetry (PIV) analysis revealed a megasonic wave-induced streaming effect that homogenized temperature differences within the chamber to <1 % under natural convective conditions, effectively addressing the problem of heat accumulation in localized regions. The optimal inter-plate distance between parallel heaters is critical; a reduced inter-plate distance enhances flow interactions between the heater surfaces, allowing confined streaming flow to impinge on and sweep across both boundary layers, thereby augmenting the cooling effect. In contrast, the spacing between the heaters increased, the acoustic streaming beam expanded, and its maximum velocity decreased due to the transformation of acoustic energy into beam enlargement, requiring a greater drive force to overcome acoustic energy attenuation and fluid viscosity. Additionally, the heat transfer effectiveness by megasonic waves is heat-flux dependent; strong acoustic streaming significantly reduces the thermal boundary layer at relatively low heat fluxes, resulting in more uniform temperatures. However, at higher fluxes, the waves' disruptive effect still sweeps away the thermal boundary layer with a relatively high-velocity stream, despite its thickness and vigorous natural convection, further improving heat transfer. These findings suggest that combining megasonic waves with dielectric liquids in two-phase immersion cooling systems could substantially improve thermal management in small electronic components and batteries.
{"title":"Megasonic wave enhanced heat transfer in a rectangular chamber filled with HFE-7100 fluid","authors":"Teerapat Thungthong , Keita Ando , Shumpei Funatani , Tatsuo Sawada , Gasidit Panomsuwan , Supacharee Roddecha , Weerachai Chaiworapuek","doi":"10.1016/j.ijheatmasstransfer.2025.126772","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126772","url":null,"abstract":"<div><div>This study experimentally investigated heat transfer and flow characteristics under natural convection in a closed rectangular chamber filled with HFE-7100 fluid, employing megasonic waves. Experiments using parallel heated plates with varying megasonic source distances and inter-plate spacings demonstrated a maximum heat transfer enhancement of 755 %. Particle image velocimetry (PIV) analysis revealed a megasonic wave-induced streaming effect that homogenized temperature differences within the chamber to <1 % under natural convective conditions, effectively addressing the problem of heat accumulation in localized regions. The optimal inter-plate distance between parallel heaters is critical; a reduced inter-plate distance enhances flow interactions between the heater surfaces, allowing confined streaming flow to impinge on and sweep across both boundary layers, thereby augmenting the cooling effect. In contrast, the spacing between the heaters increased, the acoustic streaming beam expanded, and its maximum velocity decreased due to the transformation of acoustic energy into beam enlargement, requiring a greater drive force to overcome acoustic energy attenuation and fluid viscosity. Additionally, the heat transfer effectiveness by megasonic waves is heat-flux dependent; strong acoustic streaming significantly reduces the thermal boundary layer at relatively low heat fluxes, resulting in more uniform temperatures. However, at higher fluxes, the waves' disruptive effect still sweeps away the thermal boundary layer with a relatively high-velocity stream, despite its thickness and vigorous natural convection, further improving heat transfer. These findings suggest that combining megasonic waves with dielectric liquids in two-phase immersion cooling systems could substantially improve thermal management in small electronic components and batteries.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126772"},"PeriodicalIF":5.0,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143354546","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}
Pub Date : 2025-02-06DOI: 10.1016/j.ijheatmasstransfer.2025.126769
Jinya Liu, Huiying Wu, Xia Hua, Jiru Wei, Zhenyu Liu
The silicon-based hybrid distributed jet/inline pin-fin microchannel (JIPM) and distributed jet/staggered pin-fin microchannel (JSPM) heat sinks are proposed and constructed in this paper for ultra-high heat flux (>103 W/cm2) chip-level cooling with dielectric fluid HFE-7100. By combined use of high-speed microscopic visualization and multi-parameter simultaneous measurement technology, the boiling heat transfer characteristics, pressure drop characteristics, and thermal-hydraulic performances of JIPM and JSPM heat sinks with jet velocities (uj) of 0.86∼2.58 m/s and inlet subcoolings (ΔTsub) of 21∼41 °C are experimentally investigated and compared with those of distributed jet/smooth microchannel (JSM) heat sink. The results show that compared with JSM: 1) both JIPM and JSPM can pre-trigger the onset of nucleate boiling (decreased the incipient wall superheats by up to 10.47 °C and 11.03 °C, respectively) due to the increase in nucleation sites; 2) critical heat fluxes for JIPM and JSPM are improved significantly (increased by 107 %∼140 % and 113 %∼149 %, respectively) because stable annular flow, which can prevent the local dry-out, is formed in these pin-fin microchannels. In particular, the JSPM heat sink can dissipate an ultra-high heat flux of 1041W/cm2 at a small pressure drop of 66.3kPa when uj = 2.58 m/s and ΔTsub = 31 °C; 3) significant increases in heat transfer coefficient (HTC) (increased by 143 %∼159 % and 148 %∼169 %, respectively) and decreases in effective thermal resistance (decreased by 55.0 %∼59.2 % and 55.8 %∼60.5 %, respectively) are achieved for JIPM and JSPM because of their larger heat transfer areas and more nucleation sites. Moreover, JSPM has higher HTC and lower thermal resistance than JIPM due to the enhancement of fluid disturbance and prevention of bubble coalescence; 4) excellent base temperature uniformity and flow boiling stability are obtained for both JIPM and JSPM because the pin-fin structures in these microchannels help to enhance fluid disturbance, promote phase uniform distribution, and prevent reverse flow; 5) although the enhancement in heat transfer is at the cost of the increase in pressure drop, JIPM and JSPM have superior comprehensive thermal-hydraulic performances than JSM, with maximum COPs reaching 2967 and 2683, respectively.
{"title":"Ultra-high heat flux boiling heat transfer of HFE-7100 in silicon-based distributed jet/pin-fin microchannel heat sinks","authors":"Jinya Liu, Huiying Wu, Xia Hua, Jiru Wei, Zhenyu Liu","doi":"10.1016/j.ijheatmasstransfer.2025.126769","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126769","url":null,"abstract":"<div><div>The silicon-based hybrid <strong>distributed jet/inline pin-fin microchannel</strong> (<strong>JIPM</strong>) and <strong>distributed jet/staggered pin-fin microchannel</strong> (<strong>JSPM</strong>) heat sinks are proposed and constructed in this paper for ultra-high heat flux (>10<sup>3</sup> W/cm<sup>2</sup>) chip-level cooling with dielectric fluid HFE-7100. By combined use of high-speed microscopic visualization and multi-parameter simultaneous measurement technology, the boiling heat transfer characteristics, pressure drop characteristics, and thermal-hydraulic performances of JIPM and JSPM heat sinks with jet velocities (<em>u</em><sub>j</sub>) of 0.86∼2.58 m/s and inlet subcoolings (Δ<em>T</em><sub>sub</sub>) of 21∼41 °C are experimentally investigated and compared with those of <strong>distributed jet/smooth microchannel (JSM)</strong> heat sink. The results show that <strong>compared with JSM</strong>: 1) both JIPM and JSPM can pre-trigger the onset of nucleate boiling (decreased the incipient wall superheats by up to 10.47 °C and 11.03 °C, respectively) due to the increase in nucleation sites; 2) critical heat fluxes for JIPM and JSPM are improved significantly (increased by 107 %∼140 % and 113 %∼149 %, respectively) because stable annular flow, which can prevent the local dry-out, is formed in these pin-fin microchannels. <strong>In particular, the JSPM heat sink can dissipate an ultra-high heat flux of 1041</strong> <strong>W/cm<sup>2</sup> at a small pressure drop of 66.3</strong> <strong>kPa</strong> when <em>u</em><sub>j</sub> = 2.58 m/s and Δ<em>T</em><sub>sub</sub> = 31 °C; 3) significant increases in heat transfer coefficient (HTC) (increased by 143 %∼159 % and 148 %∼169 %, respectively) and decreases in effective thermal resistance (decreased by 55.0 %∼59.2 % and 55.8 %∼60.5 %, respectively) are achieved for JIPM and JSPM because of their larger heat transfer areas and more nucleation sites. Moreover, JSPM has higher HTC and lower thermal resistance than JIPM due to the enhancement of fluid disturbance and prevention of bubble coalescence; 4) excellent base temperature uniformity and flow boiling stability are obtained for both JIPM and JSPM because the pin-fin structures in these microchannels help to enhance fluid disturbance, promote phase uniform distribution, and prevent reverse flow; 5) although the enhancement in heat transfer is at the cost of the increase in pressure drop, JIPM and JSPM have superior comprehensive thermal-hydraulic performances than JSM, with maximum COPs reaching 2967 and 2683, respectively.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126769"},"PeriodicalIF":5.0,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143308735","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}
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