When a droplet resting on a surface, its shape can be nonspherical or asymmetrical due to the surface heterogeneity, and surface temperature and evaporation flux may distribute asymmetrically during evaporation process thereafter. The evaporation of a nonspherical sessile droplet was simulated regarding heat and mass transfer process in this paper, which consists of part of a spherical cap and part of an ellipsoidal cap. Due to its asymmetrical shape, the surface temperature, saturated vapor concentration and evaporation flux distribute asymmetrically. The average surface temperature and average saturated vapor concentration are higher at ellipsoid side, but the average evaporation flux is higher at sphere side. Furthermore, due to the bigger curvature radius at ellipsoid side, the droplet evaporates faster at this side.
{"title":"Numerical Simulation on the Evaporation of a Nonspherical Sessile Droplet","authors":"Wenbin Cui, B. Fu","doi":"10.1115/mnhmt2019-3987","DOIUrl":"https://doi.org/10.1115/mnhmt2019-3987","url":null,"abstract":"\u0000 When a droplet resting on a surface, its shape can be nonspherical or asymmetrical due to the surface heterogeneity, and surface temperature and evaporation flux may distribute asymmetrically during evaporation process thereafter. The evaporation of a nonspherical sessile droplet was simulated regarding heat and mass transfer process in this paper, which consists of part of a spherical cap and part of an ellipsoidal cap. Due to its asymmetrical shape, the surface temperature, saturated vapor concentration and evaporation flux distribute asymmetrically. The average surface temperature and average saturated vapor concentration are higher at ellipsoid side, but the average evaporation flux is higher at sphere side. Furthermore, due to the bigger curvature radius at ellipsoid side, the droplet evaporates faster at this side.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"331 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124666554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Magnetic polariton (MP) that couples electromagnetic waves with magnetic excitation can be predicted by equivalent inductor-capacitor (LC) circuit model. However, when the resonance frequencies of MP and surface phonon polariton (SPhP) is close, the absorption peak predicted by the previous LC circuit model are far different from solving electromagnetic field calculation results. Absorption enhancement with a SiC slit array is theoretically demonstrated within the SiC phonon absorption band with Finite-difference time-domain (FDTD) method. The electromagnetic field distributions confirm the interactions between SPhP and MP. Taking the effects of interactions between MP and SPhP into account, the improved LC circuit model is employed to predict MP1 resonance condition and the method for predicting the multi-order MP resonance conditions is given. This study may contribute to the oriented design of thermal radiative properties and micro/nanostructures metamaterials thermal radiative properties database building.
{"title":"Predicting Multi-Order Magnetic Polaritons Resonance in SiC Slit Arrays by Improved LC Circuit Model","authors":"Yanming Guo, Y. Shuai","doi":"10.1115/mnhmt2019-4147","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4147","url":null,"abstract":"\u0000 Magnetic polariton (MP) that couples electromagnetic waves with magnetic excitation can be predicted by equivalent inductor-capacitor (LC) circuit model. However, when the resonance frequencies of MP and surface phonon polariton (SPhP) is close, the absorption peak predicted by the previous LC circuit model are far different from solving electromagnetic field calculation results. Absorption enhancement with a SiC slit array is theoretically demonstrated within the SiC phonon absorption band with Finite-difference time-domain (FDTD) method. The electromagnetic field distributions confirm the interactions between SPhP and MP. Taking the effects of interactions between MP and SPhP into account, the improved LC circuit model is employed to predict MP1 resonance condition and the method for predicting the multi-order MP resonance conditions is given. This study may contribute to the oriented design of thermal radiative properties and micro/nanostructures metamaterials thermal radiative properties database building.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121316514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study numerically investigated the condensation heat transfer and flow characteristics of refrigerants R134a in rectangular minichannels. Three-dimensional simulations were carried out at different mass flux values, vapor qualities and gravity conditions through using the VOF model, the turbulence model and the phase transition model. The effects of various parameters on the surface heat transfer coefficient and the friction pressure gradient is clarified. The condensation process is found to be enhanced due to the increase of vapor quality and mass flow, while the friction pressure gradient decreases with the decrease of vapor quality and mass flow. According to the data obtained from the simulation, the liquid film tends to accumulate along the corner of the cross section in retangular minichannel. And the thickness of liquid film increased with the decrease of mass flux and vapor quality.
{"title":"Numerical Investigation of Condensation Heat Transfer Characteristics of R134A in Rectangular Minichannel","authors":"Di Lv, Wei Li, Jingzhi Zhang","doi":"10.1115/mnhmt2019-3950","DOIUrl":"https://doi.org/10.1115/mnhmt2019-3950","url":null,"abstract":"\u0000 This study numerically investigated the condensation heat transfer and flow characteristics of refrigerants R134a in rectangular minichannels. Three-dimensional simulations were carried out at different mass flux values, vapor qualities and gravity conditions through using the VOF model, the turbulence model and the phase transition model. The effects of various parameters on the surface heat transfer coefficient and the friction pressure gradient is clarified. The condensation process is found to be enhanced due to the increase of vapor quality and mass flow, while the friction pressure gradient decreases with the decrease of vapor quality and mass flow. According to the data obtained from the simulation, the liquid film tends to accumulate along the corner of the cross section in retangular minichannel. And the thickness of liquid film increased with the decrease of mass flux and vapor quality.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126211693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ma Xianfeng, Gen Li, X. Zheng, Xiaozhong Wang, Zhongcheng Wang, Yulong Ji
The usage of low melting temperature alloys (LMAs) as thermal interface materials (TIMs) has attracted more and more attention for their high thermal conductivity. However, the wettability between liquid metal and ordinary metal surface was poor, which results in high thermal interface resistance. The thermal and physical properties of LMAs can be modified by adding nano or micro particles. In this study, the room temperature liquid metal (gallium, indium and tin eutectic) was used as TIM and its properties were modified by mixing magnetic nickel particles. Further, the effects of magnetic field application on the thermal performance of modified LMAs were evaluated by steady state method with specially designed sample holder. Results showed that the thermal conductivity of liquid metal mixed with nickel particle increased from 27.33 W/(m · K) to 33.33 W/(m · K) with the application of magnetic field.
{"title":"Thermal Property Enhancement of Liquid Metal Used As Thermal Interface Material by Mixing Magnetic Particles","authors":"Ma Xianfeng, Gen Li, X. Zheng, Xiaozhong Wang, Zhongcheng Wang, Yulong Ji","doi":"10.1115/mnhmt2019-4155","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4155","url":null,"abstract":"\u0000 The usage of low melting temperature alloys (LMAs) as thermal interface materials (TIMs) has attracted more and more attention for their high thermal conductivity. However, the wettability between liquid metal and ordinary metal surface was poor, which results in high thermal interface resistance. The thermal and physical properties of LMAs can be modified by adding nano or micro particles. In this study, the room temperature liquid metal (gallium, indium and tin eutectic) was used as TIM and its properties were modified by mixing magnetic nickel particles. Further, the effects of magnetic field application on the thermal performance of modified LMAs were evaluated by steady state method with specially designed sample holder. Results showed that the thermal conductivity of liquid metal mixed with nickel particle increased from 27.33 W/(m · K) to 33.33 W/(m · K) with the application of magnetic field.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115438994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Hasan, Md. Hafijur Rahman, Salauddin Omar, C. Akhter
Present study has been performed to understand condensation characteristics of argon vapor over nano-structured surface using non equilibrium molecular dynamics (MD) simulation. Main focus of this study is to explore the effect of condensation surface increment due to presence of nano-structure (considering flat surface as reference), solid-liquid interfacial wettability and condensation wall temperature. The simulation domain is a horizontal cuboid system that has two platinum walls at two opposite ends, left wall as the evaporation wall and the right wall as the condensation wall. Liquid argon was placed over the evaporation wall and the rest of the domain was filled with argon vapor. Various platinum nano-structured configurations were used to vary the surface area of the condensation wall. The system is first equilibrated at 90 K for a while and the evaporation of liquid argon is achieved by increasing the evaporation wall temperature at 130 K. The condensation of argon vapor is assumed for two different condensation temperatures such as 90 K and 110 K. The results indicate that condensation improves with condensation surface increment due to presence of nano-structure. Also it shows that the effect of condensation surface increment due to presence of nano-structure is drastically reduced with increasing solid-liquid interfacial wettability. The condensation at 110 K was poor compared to condensation at 90 K. The obtained results has been presented and discussed from macroscopic approach in terms of condensation mass flux, thermodynamic heat flux and time averaged wall heat flux.
{"title":"Atomistic Modeling of Condensation Over Nano-Structured Surface","authors":"M. Hasan, Md. Hafijur Rahman, Salauddin Omar, C. Akhter","doi":"10.1115/mnhmt2019-4247","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4247","url":null,"abstract":"\u0000 Present study has been performed to understand condensation characteristics of argon vapor over nano-structured surface using non equilibrium molecular dynamics (MD) simulation. Main focus of this study is to explore the effect of condensation surface increment due to presence of nano-structure (considering flat surface as reference), solid-liquid interfacial wettability and condensation wall temperature. The simulation domain is a horizontal cuboid system that has two platinum walls at two opposite ends, left wall as the evaporation wall and the right wall as the condensation wall. Liquid argon was placed over the evaporation wall and the rest of the domain was filled with argon vapor. Various platinum nano-structured configurations were used to vary the surface area of the condensation wall. The system is first equilibrated at 90 K for a while and the evaporation of liquid argon is achieved by increasing the evaporation wall temperature at 130 K. The condensation of argon vapor is assumed for two different condensation temperatures such as 90 K and 110 K. The results indicate that condensation improves with condensation surface increment due to presence of nano-structure. Also it shows that the effect of condensation surface increment due to presence of nano-structure is drastically reduced with increasing solid-liquid interfacial wettability. The condensation at 110 K was poor compared to condensation at 90 K. The obtained results has been presented and discussed from macroscopic approach in terms of condensation mass flux, thermodynamic heat flux and time averaged wall heat flux.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"286 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116442325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qin Sun, Jian Qu, Jianping Yuan, Hai Wang, S. Thompson
The oscillating heat pipe is considered a promising candidate for high-efficiency and compact thermal control for next-generation electronics. In this paper, the visualized flow and heat transfer characteristics of two silicon-based micro oscillating heat pipes (micro-OHPs) with expanding and straight channels, respectively, were experimentally investigated. The overall size of these two micro-OHPs are both 28 mm × 23 mm × 1.025 mm and have thirty rectangular cross-section channels. The hydraulic diameter of parallel direct channel is 332.4 μm, while they are about 364.4 and 287.0 μm at the two ends of expanding channel, respectively. R141b was used as the working fluid with the volumetric filling ratio of 50%. Inside these two micro-devices, the fluid oscillating motion, including unidirectional movement and intermittent stopovers, was observed at the quasi-steady oscillation state, accompanied by bubbly flow, slug flow and annular/semi-annular flow in microchannels. The micro-OHP with expanding channels possessed better thermal performance and could achieve ephemeral circulation flow, while poorer heat transfer performance occurred for the micro-OHP with straight channels due to more localized slug/plug oscillations and intermittent stopovers. The oscillating amplitudes of liquid slugs are presented to estimate the flow behavior of working fluid inside micro-OHPs. The introduction of expanding channels in a micro-OHP is beneficial for realizing the more robust oscillating motion of liquid slugs with larger oscillating amplitudes for heat transfer enhancement.
振荡热管被认为是下一代电子产品高效紧凑热控制的有前途的候选者。实验研究了两种膨胀型和直线型硅基微振荡热管的流动和传热特性。两种微ohps的整体尺寸均为28 mm × 23 mm × 1.025 mm，具有30个矩形截面通道。平行直接通道的水力直径为332.4 μm，扩张通道两端的水力直径分别约为364.4 μm和287.0 μm。采用R141b作为工质，体积填充比为50%。在两个微装置内部，流体处于准稳态振荡状态，包括单向运动和间歇停留，微通道内存在气泡流、段塞流和环形/半环形流动。膨胀通道的微ohp传热性能较好，可以实现短暂循环流动，而直线型微ohp传热性能较差，主要是局部段塞/塞振荡和间歇停留。利用液体段塞的振荡幅值来估计微ohps内工作流体的流动特性。在微ohp中引入膨胀通道有利于实现振荡幅度更大的液体段塞振荡运动的鲁棒性，从而增强传热。
{"title":"Fluid Flow and Heat Transfer Characteristics of Micro Oscillating Heat Pipes With and Without Expanding Channels","authors":"Qin Sun, Jian Qu, Jianping Yuan, Hai Wang, S. Thompson","doi":"10.1115/mnhmt2019-3976","DOIUrl":"https://doi.org/10.1115/mnhmt2019-3976","url":null,"abstract":"\u0000 The oscillating heat pipe is considered a promising candidate for high-efficiency and compact thermal control for next-generation electronics. In this paper, the visualized flow and heat transfer characteristics of two silicon-based micro oscillating heat pipes (micro-OHPs) with expanding and straight channels, respectively, were experimentally investigated. The overall size of these two micro-OHPs are both 28 mm × 23 mm × 1.025 mm and have thirty rectangular cross-section channels. The hydraulic diameter of parallel direct channel is 332.4 μm, while they are about 364.4 and 287.0 μm at the two ends of expanding channel, respectively. R141b was used as the working fluid with the volumetric filling ratio of 50%. Inside these two micro-devices, the fluid oscillating motion, including unidirectional movement and intermittent stopovers, was observed at the quasi-steady oscillation state, accompanied by bubbly flow, slug flow and annular/semi-annular flow in microchannels. The micro-OHP with expanding channels possessed better thermal performance and could achieve ephemeral circulation flow, while poorer heat transfer performance occurred for the micro-OHP with straight channels due to more localized slug/plug oscillations and intermittent stopovers. The oscillating amplitudes of liquid slugs are presented to estimate the flow behavior of working fluid inside micro-OHPs. The introduction of expanding channels in a micro-OHP is beneficial for realizing the more robust oscillating motion of liquid slugs with larger oscillating amplitudes for heat transfer enhancement.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129766705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Inspired by a few phenomena in nature such as the lotus leaf, red rose petal, gecko’s feet and Nepenthes Alata plant, much attention has been paid to use simple and feasible means to achieve remarkable wetting behaviour for many applications in various areas including self-cleaning for building exteriors and windshields, oil/water separation, anti-icing, liquid collecting, anti-fogging and anti-corrosion. Based on the established theoretical models, wetting behaviour of a liquid droplet obtained by molecular dynamics simulation method is generally in good agreement with the experimental results. In macro and micro scale, the previous theories can explain and predict the wetting behaviors well. However, these theories are invalid for nanoscale. It is essential to reveal the underlying physical mechanism of the wetting behaviors of the droplet on solid surface with nanoroughness. Extensive studies on nanosale wettability focus on the effect of nano structures on wettability state. Desired wetting behavior of rough material surface achieved by nanosize reentrant geometry like “T” or mushroom shape and other variant geometry with solid overhangs has been widely used in self-cleaning surfaces, heat exchange and many applications. For example, “T” shape groove with different depths and widths under nanoscale has been considered to confer superhydrophobicity to hydrophilic surfaces gradually. In this paper, wettability transition of a liquid droplet on geometrically heterogeneous solid substrate with nanoscale structures of inverted triangular grooves is investigated by using molecular dynamics simulation method under the parameter space spanned by structure geometry and solid-liquid molecular interaction potential strength. Three wettability states, namely Cassie nonwetting state, Cassie-to-Wenzel transition state and Wenzel wetting state, are identified with various geometries and potential strength. For Cassie nonwetting state, increasing height of the triangles has less effect on wettability transition with weak solid-liquid molecular interaction. Besides, the Cassie nonwetting state is less sensitive to different interval between the triangles as solid-liquid molecular interaction is weak. For Cassie-to-Wenzel transition state, increasing height of the triangles and decreasing interval between the triangles decrease wettability. For Wenzel wetting state, increasing interval between the triangles with low height increases wettability. With strong solid-liquid molecular interaction, different interval between the triangles results in wetting state transition from Wenzel to transition state. What’s more, liquid droplet changes its state from Wenzel wetting state to Cassie-to-Wenzel transition state with increasing height of the triangles or decreasing interval between the triangles. Three wettability transition regions are identified in the parameter space.
{"title":"Wettability Transition of a Liquid Droplet on Solid Surface With Nanoscale Inverted Triangular Grooves","authors":"Meiling Cai, Yuxiu Li, Ying Chen, Jinliang Xu, Longyan Zhang, Junpeng Lei","doi":"10.1115/mnhmt2019-4217","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4217","url":null,"abstract":"\u0000 Inspired by a few phenomena in nature such as the lotus leaf, red rose petal, gecko’s feet and Nepenthes Alata plant, much attention has been paid to use simple and feasible means to achieve remarkable wetting behaviour for many applications in various areas including self-cleaning for building exteriors and windshields, oil/water separation, anti-icing, liquid collecting, anti-fogging and anti-corrosion. Based on the established theoretical models, wetting behaviour of a liquid droplet obtained by molecular dynamics simulation method is generally in good agreement with the experimental results. In macro and micro scale, the previous theories can explain and predict the wetting behaviors well. However, these theories are invalid for nanoscale. It is essential to reveal the underlying physical mechanism of the wetting behaviors of the droplet on solid surface with nanoroughness.\u0000 Extensive studies on nanosale wettability focus on the effect of nano structures on wettability state. Desired wetting behavior of rough material surface achieved by nanosize reentrant geometry like “T” or mushroom shape and other variant geometry with solid overhangs has been widely used in self-cleaning surfaces, heat exchange and many applications. For example, “T” shape groove with different depths and widths under nanoscale has been considered to confer superhydrophobicity to hydrophilic surfaces gradually.\u0000 In this paper, wettability transition of a liquid droplet on geometrically heterogeneous solid substrate with nanoscale structures of inverted triangular grooves is investigated by using molecular dynamics simulation method under the parameter space spanned by structure geometry and solid-liquid molecular interaction potential strength. Three wettability states, namely Cassie nonwetting state, Cassie-to-Wenzel transition state and Wenzel wetting state, are identified with various geometries and potential strength. For Cassie nonwetting state, increasing height of the triangles has less effect on wettability transition with weak solid-liquid molecular interaction. Besides, the Cassie nonwetting state is less sensitive to different interval between the triangles as solid-liquid molecular interaction is weak. For Cassie-to-Wenzel transition state, increasing height of the triangles and decreasing interval between the triangles decrease wettability. For Wenzel wetting state, increasing interval between the triangles with low height increases wettability. With strong solid-liquid molecular interaction, different interval between the triangles results in wetting state transition from Wenzel to transition state. What’s more, liquid droplet changes its state from Wenzel wetting state to Cassie-to-Wenzel transition state with increasing height of the triangles or decreasing interval between the triangles. Three wettability transition regions are identified in the parameter space.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"601 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123176098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent microCT imaging study has demonstrated that local heating caused a much larger nanoparticle distribution volume in tumors than that in tumors without localized heating, suggesting possible nanoparticle redistribution/migration during heating. In this study, a theoretical simulation is performed to evaluate to what extent the nanoparticle redistribution affects the temperature elevations and thermal dosage required to cause permanent thermal damage to PC3 tumors. Two tumor groups with similar sizes are selected. The control group consists of five PC3 tumors with nanoparticles distribution without heating, while the experimental group consists of another five resected PC3 tumors with nanoparticles distribution obtained after 25 minutes of local heating. Each generated tumor model is attached to a mouse body model by microCT scans. A previously determined relationship between the nanoparticle concentration distribution and the volumetric heat generation rate is implemented in the theoretical simulation of temperature elevations during magnetic nanoparticle hyperthermia. Our simulation results show that the average steady state temperature elevation in the tumors of the control group is higher than that in the experimental group when the nanoparticles are more spreading from the tumor center to tumor periphery (control group: 64.03±3.2°C vs. experimental group: 62.04±3.07°C). Further we assess the thermal dosage needed to cause 100% permanent thermal damage (Arrhenius integral Ω = 4) to the entire tumor, based on the assumption of unchanged nanoparticle distribution during heating. The average heating time based on the experimental setting from our previous studies demonstrates significantly different designs. Specifically, the average heating time for the control group is 24.3 minutes. However, the more spreading of nanoparticles to tumor periphery in the experimental group results in a much longer heating time of 38.1 minutes, 57° longer than that in the control group, to induce permanent thermal damage to the entire tumor. The results from this study suggest that the heating time needed when considering dynamic nanoparticle migration during heating is probably between 24 to 38 minutes. In conclusion, the study demonstrates the importance of including dynamic nanoparticle spreading during heating into theoretical simulation of temperature elevations in tumors to determine accurate thermal dosage needed in magnetic nanoparticle hyperthermia design.
{"title":"Temperature Distribution and Thermal Dosage Affected by Nanoparticle Distribution in Tumours During Magnetic Nanoparticle Hyperthermia","authors":"Manpreet Singh, Qimei Gu, Ronghui Ma, Liang Zhu","doi":"10.1115/mnhmt2019-4233","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4233","url":null,"abstract":"\u0000 Recent microCT imaging study has demonstrated that local heating caused a much larger nanoparticle distribution volume in tumors than that in tumors without localized heating, suggesting possible nanoparticle redistribution/migration during heating. In this study, a theoretical simulation is performed to evaluate to what extent the nanoparticle redistribution affects the temperature elevations and thermal dosage required to cause permanent thermal damage to PC3 tumors. Two tumor groups with similar sizes are selected. The control group consists of five PC3 tumors with nanoparticles distribution without heating, while the experimental group consists of another five resected PC3 tumors with nanoparticles distribution obtained after 25 minutes of local heating. Each generated tumor model is attached to a mouse body model by microCT scans. A previously determined relationship between the nanoparticle concentration distribution and the volumetric heat generation rate is implemented in the theoretical simulation of temperature elevations during magnetic nanoparticle hyperthermia. Our simulation results show that the average steady state temperature elevation in the tumors of the control group is higher than that in the experimental group when the nanoparticles are more spreading from the tumor center to tumor periphery (control group: 64.03±3.2°C vs. experimental group: 62.04±3.07°C). Further we assess the thermal dosage needed to cause 100% permanent thermal damage (Arrhenius integral Ω = 4) to the entire tumor, based on the assumption of unchanged nanoparticle distribution during heating. The average heating time based on the experimental setting from our previous studies demonstrates significantly different designs. Specifically, the average heating time for the control group is 24.3 minutes. However, the more spreading of nanoparticles to tumor periphery in the experimental group results in a much longer heating time of 38.1 minutes, 57° longer than that in the control group, to induce permanent thermal damage to the entire tumor. The results from this study suggest that the heating time needed when considering dynamic nanoparticle migration during heating is probably between 24 to 38 minutes. In conclusion, the study demonstrates the importance of including dynamic nanoparticle spreading during heating into theoretical simulation of temperature elevations in tumors to determine accurate thermal dosage needed in magnetic nanoparticle hyperthermia design.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":" 22","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132041076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present work in nanofluids is focusing into using the electro-kinetic phenomenal occurring around nanoparticles immersed in a base fluid as a method to stabilize a nanofluid and enhance its thermal conductivity. The electro-kinetic physic establishes, that when an electrolyte solution is in contact with a solid, an electric double layer (EDL) is produced on the solid surface. Due to the high concentration of ions with the same charge around of the particle surface, “it is possible to stabilize a nanofluid by the action of an electro repulsive force caused by ions over the nanoparticle surface and enhance its thermal conductivity as the concentration of the solutions increases”. The nanofluid samples were prepared by the two-step method and a continuous ultrasonication. 1wt% and 3wt% concentration (mass fraction) of Titanium oxide, Anatase (TiO2) nanoparticles, is added in an electrolyte solution (base fluid) made of different concentration of Potassium Chloride (KCl), and deionized water. The pH of the base fluid is maintained constant adding HEPES as a buffering agent. To measure the different level of stability for the nanofluid we used the thermal conductivity enhancement of the base fluid by nanoparticles. The experimental results under controlled temperature condition show that an electrolyte solution with nanoparticles after 20 days of preparation, presents a higher thermal conductivity with respect to the base fluid with an improvement rate ranging from 0.43±0.12% to 0.72±0.12% for 1wt%, and 2.15±0.17% to 3.03±0.21% for 3wt% of nanoparticles added respectively. The higher improvement shows sign of a major level of homogeneity of the nanofluid, and this behavior seems to be directly proportional to the KCl concentration.
{"title":"Electrorepulsion in Nanofluids: Experimental Characterization for a Stable Behavior","authors":"Daming Chen, D. Vasco, H. MarioDiCapua, A. Guzmán","doi":"10.1115/mnhmt2019-3980","DOIUrl":"https://doi.org/10.1115/mnhmt2019-3980","url":null,"abstract":"\u0000 The present work in nanofluids is focusing into using the electro-kinetic phenomenal occurring around nanoparticles immersed in a base fluid as a method to stabilize a nanofluid and enhance its thermal conductivity. The electro-kinetic physic establishes, that when an electrolyte solution is in contact with a solid, an electric double layer (EDL) is produced on the solid surface. Due to the high concentration of ions with the same charge around of the particle surface, “it is possible to stabilize a nanofluid by the action of an electro repulsive force caused by ions over the nanoparticle surface and enhance its thermal conductivity as the concentration of the solutions increases”. The nanofluid samples were prepared by the two-step method and a continuous ultrasonication. 1wt% and 3wt% concentration (mass fraction) of Titanium oxide, Anatase (TiO2) nanoparticles, is added in an electrolyte solution (base fluid) made of different concentration of Potassium Chloride (KCl), and deionized water. The pH of the base fluid is maintained constant adding HEPES as a buffering agent. To measure the different level of stability for the nanofluid we used the thermal conductivity enhancement of the base fluid by nanoparticles. The experimental results under controlled temperature condition show that an electrolyte solution with nanoparticles after 20 days of preparation, presents a higher thermal conductivity with respect to the base fluid with an improvement rate ranging from 0.43±0.12% to 0.72±0.12% for 1wt%, and 2.15±0.17% to 3.03±0.21% for 3wt% of nanoparticles added respectively. The higher improvement shows sign of a major level of homogeneity of the nanofluid, and this behavior seems to be directly proportional to the KCl concentration.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124804012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Zhao, Huan Lin, F. Su, B. Fu, Hongbin Ma, Bohan Tian
A significantly higher heat transfer coefficient can be achieved through thin-film evaporation. Nanofluids also have significant enhancements in heat transfer. In the current investigation, based on the principle of conservation of momentum and the Young-Laplace equation, considering the effects of bulk flow and nanofluids concentration variation, a mathematical model of evaporative heat transfer of nanofluids is established. The different performances of different concentrations of nanofluids in the thin film evaporation heat transfer process are discussed. The results show that with the change of nanofluids concentration, the surface tension, dynamic viscosity, thermal conductivity and density will be changed, and surface tension plays an important role in the thin film evaporation heat transfer process. That will lead to a significant effect on the thin-film profile, interface temperature, heat flux in the thin-film region of the nanofluids.
{"title":"Theoretical Analysis of Evaporation Heat Transfer in the Thin-Film Region of Nanofluids","authors":"N. Zhao, Huan Lin, F. Su, B. Fu, Hongbin Ma, Bohan Tian","doi":"10.1115/mnhmt2019-3970","DOIUrl":"https://doi.org/10.1115/mnhmt2019-3970","url":null,"abstract":"\u0000 A significantly higher heat transfer coefficient can be achieved through thin-film evaporation. Nanofluids also have significant enhancements in heat transfer. In the current investigation, based on the principle of conservation of momentum and the Young-Laplace equation, considering the effects of bulk flow and nanofluids concentration variation, a mathematical model of evaporative heat transfer of nanofluids is established. The different performances of different concentrations of nanofluids in the thin film evaporation heat transfer process are discussed. The results show that with the change of nanofluids concentration, the surface tension, dynamic viscosity, thermal conductivity and density will be changed, and surface tension plays an important role in the thin film evaporation heat transfer process. That will lead to a significant effect on the thin-film profile, interface temperature, heat flux in the thin-film region of the nanofluids.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122486415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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