Pub Date : 2021-04-03DOI: 10.1080/15567265.2021.1926607
Guoding Xu, Jian Sun, Hongmin Mao, Z. Cao, Xiying Ma
ABSTRACT We propose a thermal modulation structure made of two identical SiO2 slabs coated by Dirac semimetal (DSM) films and separated by a nanoscale vacuum gap. The energy transmission probability reveals that the coupled surface plasmon polaritons (SPPs) between the two DSM films, and the surface phonon polaritons (SPhPs) supported by the SiO2 substrate can vary sensitively with the Fermi level, the degenerate factor of 3D Dirac points and the thickness of the DSM film, thus providing the possibilities for modulating the radiative heat transfer by tuning these parameters. Based on Maxwell’s equations incorporating fluctuational electrodynamics, the effects of these parameters on the heat transfer coefficient and the thermal modulation contrast are numerically analyzed. Under proper parameters, higher modulation contrasts are obtained by continuously tuning the Fermi level from 0.05 eV to 0.3 eV. The obtained results might be helpful in designing a DSM-based thermal modulator with higher modulation contrasts.
{"title":"Modulating Near-Field Radiative Heat Transfer through Thin Dirac Semimetal Films","authors":"Guoding Xu, Jian Sun, Hongmin Mao, Z. Cao, Xiying Ma","doi":"10.1080/15567265.2021.1926607","DOIUrl":"https://doi.org/10.1080/15567265.2021.1926607","url":null,"abstract":"ABSTRACT We propose a thermal modulation structure made of two identical SiO2 slabs coated by Dirac semimetal (DSM) films and separated by a nanoscale vacuum gap. The energy transmission probability reveals that the coupled surface plasmon polaritons (SPPs) between the two DSM films, and the surface phonon polaritons (SPhPs) supported by the SiO2 substrate can vary sensitively with the Fermi level, the degenerate factor of 3D Dirac points and the thickness of the DSM film, thus providing the possibilities for modulating the radiative heat transfer by tuning these parameters. Based on Maxwell’s equations incorporating fluctuational electrodynamics, the effects of these parameters on the heat transfer coefficient and the thermal modulation contrast are numerically analyzed. Under proper parameters, higher modulation contrasts are obtained by continuously tuning the Fermi level from 0.05 eV to 0.3 eV. The obtained results might be helpful in designing a DSM-based thermal modulator with higher modulation contrasts.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"101 - 115"},"PeriodicalIF":4.1,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1926607","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42960476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-03-25DOI: 10.1080/15567265.2021.1903631
S. Movaghgharnezhad, J. Darabi
ABSTRACT Heat pipes and vapor chambers have been widely utilized for the thermal management of electronic devices due to their effective heat transport, passive cooling operation, and high reliability. In these devices, a wick structure transports a working fluid from the heat sink to the heat source via capillary action in the wick structure. This paper provides a broad overview of the latest studies on the development of Micro-/Nanostructured wicks for passive cooling systems. Micro/nanopillar-based wick structures provide a high capillary pressure, a large permeability, and larger areas for evaporation, resulting in a significantly higher heat removal capability and dryout heat flux. A special emphasis is placed on the various types and geometries of wick structures and their performance. Additionally, limitations and recommendations for future investigations are discussed.
{"title":"Advanced Micro-/Nanostructured Wicks for Passive Phase-Change Cooling Systems","authors":"S. Movaghgharnezhad, J. Darabi","doi":"10.1080/15567265.2021.1903631","DOIUrl":"https://doi.org/10.1080/15567265.2021.1903631","url":null,"abstract":"ABSTRACT Heat pipes and vapor chambers have been widely utilized for the thermal management of electronic devices due to their effective heat transport, passive cooling operation, and high reliability. In these devices, a wick structure transports a working fluid from the heat sink to the heat source via capillary action in the wick structure. This paper provides a broad overview of the latest studies on the development of Micro-/Nanostructured wicks for passive cooling systems. Micro/nanopillar-based wick structures provide a high capillary pressure, a large permeability, and larger areas for evaporation, resulting in a significantly higher heat removal capability and dryout heat flux. A special emphasis is placed on the various types and geometries of wick structures and their performance. Additionally, limitations and recommendations for future investigations are discussed.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"116 - 135"},"PeriodicalIF":4.1,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1903631","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43513200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-02-03DOI: 10.1080/15567265.2021.1902441
Y. Quan, Shengying Yue, Bolin Liao
ABSTRACT A thorough understanding of the microscopic picture of heat conduction in solids is critical to a broad range of applications, from thermal management of microelectronics to more efficient thermoelectric materials. The transport properties of phonons, the major microscopic heat carriers in semiconductors and insulators, particularly their scattering mechanisms, have been a central theme in microscale heat conduction research. In the past two decades, significant advancements have been made in computational and experimental efforts to probe phonon-phonon, phonon-impurity, and phonon-boundary scattering channels in detail. In contrast, electron-phonon scatterings were long thought to have negligible effects on thermal transport in most materials under ambient conditions. This article reviews the recent progress in first-principles computations and experimental methods that show clear evidence for a strong impact of electron-phonon interaction on phonon transport in a wide variety of technologically relevant solid-state materials. Under thermal equilibrium conditions, electron-phonon interactions can modify the total phonon scattering rates and renormalize the phonon frequency, as determined by the imaginary part and the real part of the phonon self-energy, respectively. Under nonequilibrium transport conditions, electron-phonon interactions can affect the coupled transport of electrons and phonons in the bulk through the “phonon/electron drag” mechanism as well as the interfacial thermal transport. Based on these recent results, we evaluate the potential use of electron-phonon interactions to control thermal transport in solids. We also provide an outlook on future directions of computational and experimental developments.
{"title":"Impact of Electron-Phonon Interaction on Thermal Transport: A Review","authors":"Y. Quan, Shengying Yue, Bolin Liao","doi":"10.1080/15567265.2021.1902441","DOIUrl":"https://doi.org/10.1080/15567265.2021.1902441","url":null,"abstract":"ABSTRACT A thorough understanding of the microscopic picture of heat conduction in solids is critical to a broad range of applications, from thermal management of microelectronics to more efficient thermoelectric materials. The transport properties of phonons, the major microscopic heat carriers in semiconductors and insulators, particularly their scattering mechanisms, have been a central theme in microscale heat conduction research. In the past two decades, significant advancements have been made in computational and experimental efforts to probe phonon-phonon, phonon-impurity, and phonon-boundary scattering channels in detail. In contrast, electron-phonon scatterings were long thought to have negligible effects on thermal transport in most materials under ambient conditions. This article reviews the recent progress in first-principles computations and experimental methods that show clear evidence for a strong impact of electron-phonon interaction on phonon transport in a wide variety of technologically relevant solid-state materials. Under thermal equilibrium conditions, electron-phonon interactions can modify the total phonon scattering rates and renormalize the phonon frequency, as determined by the imaginary part and the real part of the phonon self-energy, respectively. Under nonequilibrium transport conditions, electron-phonon interactions can affect the coupled transport of electrons and phonons in the bulk through the “phonon/electron drag” mechanism as well as the interfacial thermal transport. Based on these recent results, we evaluate the potential use of electron-phonon interactions to control thermal transport in solids. We also provide an outlook on future directions of computational and experimental developments.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"73 - 90"},"PeriodicalIF":4.1,"publicationDate":"2021-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1902441","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45365541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-02DOI: 10.1080/15567265.2021.1883165
Xiaohu Wu, C. Fu
ABSTRACT Hyperbolic volume and surface phonon polaritons have been studied extensively for enhancing the near-field radiative heat transfer (NFRHT) between hyperbolic materials. Hyperbolic volume phonon polaritons (HVPPs) describe propagating electromagnetic waves in hyperbolic materials while evanescent waves are required for excitation of hyperbolic surface phonon polaritons (HSPPs). Therefore, the dispersion relations of HVPPs and HSPPs are distinct. Here we study the interaction of HVPPs and HSPPs within the context of NFRHT between hyperbolic materials. We find that the dispersion curves of HVPPs and HSPPs in an ultrathin hyperbolic slab can connect smoothly. Particularly, we find that the topology of HVPPs can be convex and flat, rather than concave, and can be controlled by tuning the thickness of the hyperbolic slab, which has not been reported in published literature. We believe our findings presented here may help to deepen our understanding on the interaction between HVPPs and HSPPs, as well as the knowledge on the topology of HVPPs in hyperbolic materials.
{"title":"Hyperbolic volume and surface phonon polaritons excited in an ultrathin hyperbolic slab: connection of dispersion and topology","authors":"Xiaohu Wu, C. Fu","doi":"10.1080/15567265.2021.1883165","DOIUrl":"https://doi.org/10.1080/15567265.2021.1883165","url":null,"abstract":"ABSTRACT Hyperbolic volume and surface phonon polaritons have been studied extensively for enhancing the near-field radiative heat transfer (NFRHT) between hyperbolic materials. Hyperbolic volume phonon polaritons (HVPPs) describe propagating electromagnetic waves in hyperbolic materials while evanescent waves are required for excitation of hyperbolic surface phonon polaritons (HSPPs). Therefore, the dispersion relations of HVPPs and HSPPs are distinct. Here we study the interaction of HVPPs and HSPPs within the context of NFRHT between hyperbolic materials. We find that the dispersion curves of HVPPs and HSPPs in an ultrathin hyperbolic slab can connect smoothly. Particularly, we find that the topology of HVPPs can be convex and flat, rather than concave, and can be controlled by tuning the thickness of the hyperbolic slab, which has not been reported in published literature. We believe our findings presented here may help to deepen our understanding on the interaction between HVPPs and HSPPs, as well as the knowledge on the topology of HVPPs in hyperbolic materials.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"64 - 71"},"PeriodicalIF":4.1,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1883165","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43727308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2021-01-02DOI: 10.1080/15567265.2021.1881193
C. Polanco
ABSTRACT Recent advances in fabrication techniques have enabled the development of materials sculpted at the nanoscale (~10 nm). These “nano-materials” could revolutionize thermal management technologies by providing novel ways to manipulate energy propagation in solids. Atomistic simulations are critical to forging this revolution, given their ability to describe a system’s dynamics on an atom by atom basis. This topical review focuses on nonequilibrium Green’s functions (NEGF) simulations to model vibrational energy propagation at the nanoscale. NEGF is an atomistic and purely quantum mechanical approach well-suited to compute thermal transport in spatially varying systems such as “nano-materials.” This review presents the NEGF methodology from a top-to-bottom perspective, focusing on the concepts behind the mathematical expressions. We start describing the implementation of NEGF that assumes harmonic interatomic potentials (h-NEGF) and some recent advances that distinguish the transport contributions by different polarizations. This review also discusses the less common implementation of NEGF that includes the anharmonic terms of the potentials (a-NEGF), outlining existing approximations and standing challenges. Our success in tackling these challenges will determine whether we will harness the full potential of NEGF to describe thermal transport from a quantum mechanical standpoint.
{"title":"Nonequilibrium Green’s functions (NEGF) in vibrational energy transport: a topical review","authors":"C. Polanco","doi":"10.1080/15567265.2021.1881193","DOIUrl":"https://doi.org/10.1080/15567265.2021.1881193","url":null,"abstract":"ABSTRACT Recent advances in fabrication techniques have enabled the development of materials sculpted at the nanoscale (~10 nm). These “nano-materials” could revolutionize thermal management technologies by providing novel ways to manipulate energy propagation in solids. Atomistic simulations are critical to forging this revolution, given their ability to describe a system’s dynamics on an atom by atom basis. This topical review focuses on nonequilibrium Green’s functions (NEGF) simulations to model vibrational energy propagation at the nanoscale. NEGF is an atomistic and purely quantum mechanical approach well-suited to compute thermal transport in spatially varying systems such as “nano-materials.” This review presents the NEGF methodology from a top-to-bottom perspective, focusing on the concepts behind the mathematical expressions. We start describing the implementation of NEGF that assumes harmonic interatomic potentials (h-NEGF) and some recent advances that distinguish the transport contributions by different polarizations. This review also discusses the less common implementation of NEGF that includes the anharmonic terms of the potentials (a-NEGF), outlining existing approximations and standing challenges. Our success in tackling these challenges will determine whether we will harness the full potential of NEGF to describe thermal transport from a quantum mechanical standpoint.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"1 - 24"},"PeriodicalIF":4.1,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2021.1881193","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44855986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2020-12-13DOI: 10.1080/15567265.2020.1860170
S. Misyura, R. Egorov, V. Morozov, A. S. Zaitsev
ABSTRACT The behavior of self-organization of convective flows in a thin layer of liquid under point (local) heating is investigated experimentally. The interaction of thermocapillary and thermogravitational-free convection can lead both to self-organization of a cluster of micro-vortices in the form of hexagonal structures and to its partial disintegration. Correlation analysis of the velocity field shows that the characteristic convection scales change continuously over time. The largest size of the vortex flow corresponds to the layer diameter (20 mm); the integral convection scale (2.5 mm) characterizes the established interaction of vortex structures in a wide range of sizes; and the dimensions of hexagonal convective cells (80–100 µm) show the lower limit of the characteristic scale of vortex structures. The observed flow macrostructure is determined by the complex nonlinear interaction of vortices of the specified scales. The resulting value of the average integral convection scale can be effectively used to predict the convection velocity.
{"title":"Forming the Convective Flows and a Cluster of Particles under Spot Heating","authors":"S. Misyura, R. Egorov, V. Morozov, A. S. Zaitsev","doi":"10.1080/15567265.2020.1860170","DOIUrl":"https://doi.org/10.1080/15567265.2020.1860170","url":null,"abstract":"ABSTRACT The behavior of self-organization of convective flows in a thin layer of liquid under point (local) heating is investigated experimentally. The interaction of thermocapillary and thermogravitational-free convection can lead both to self-organization of a cluster of micro-vortices in the form of hexagonal structures and to its partial disintegration. Correlation analysis of the velocity field shows that the characteristic convection scales change continuously over time. The largest size of the vortex flow corresponds to the layer diameter (20 mm); the integral convection scale (2.5 mm) characterizes the established interaction of vortex structures in a wide range of sizes; and the dimensions of hexagonal convective cells (80–100 µm) show the lower limit of the characteristic scale of vortex structures. The observed flow macrostructure is determined by the complex nonlinear interaction of vortices of the specified scales. The resulting value of the average integral convection scale can be effectively used to predict the convection velocity.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"25 1","pages":"46 - 63"},"PeriodicalIF":4.1,"publicationDate":"2020-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2020.1860170","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41591023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2020-10-01DOI: 10.1080/15567265.2020.1845884
Cheng-Long Zhou, Shui-Hua Yang, Yong Zhang, H. Yi
ABSTRACT In the present work, we theoretically demonstrate that near-field radiative heat transfer (NFRHT) can be modulated and enhanced by a new energy transmission mode of evanescent wave, i.e. the nonreciprocal hyperbolic surface plasmon polaritons (NHSPPs). It is well known that by patterning a single layer of graphene sheet into ribbons, the closed circular dispersion of graphene plasmons is opened to become hyperbolic one. When a drift current is applied to a graphene ribbon, this hyperbolic model would evolve into the extremely asymmetric shape, which has never been noted in the noncontact heat exchanges at nanoscale before. Combining the analysis of dispersion distribution, we find that as the drift velocity increases, the hyperbolic mode exhibits more significant asymmetric characteristics. It is also found that under a larger gap size, the enhanced effect of NHSPPs on NFRHT can be weakened. In addition, the coupling effect of grating and drift current is investigated simultaneously. By changing the chemical potential and graphene filling factor, the positions and intensities of the modes can be modulated, and hence the NFRHT can be tuned accordingly. Finally, we have found that thanks to the nonreciprocal hyperbolic topology of the system, at a large twisted angle, the system with a large drift current velocity is more preferable to modulate the NFRHT compared with the zero-current case. In summary, the findings may open a promising pathway for highly efficient thermal management, energy harvesting, and subwavelength thermal imaging.
{"title":"Near-field electromagnetic heat transfer through nonreciprocal hyperbolic graphene plasmons","authors":"Cheng-Long Zhou, Shui-Hua Yang, Yong Zhang, H. Yi","doi":"10.1080/15567265.2020.1845884","DOIUrl":"https://doi.org/10.1080/15567265.2020.1845884","url":null,"abstract":"ABSTRACT In the present work, we theoretically demonstrate that near-field radiative heat transfer (NFRHT) can be modulated and enhanced by a new energy transmission mode of evanescent wave, i.e. the nonreciprocal hyperbolic surface plasmon polaritons (NHSPPs). It is well known that by patterning a single layer of graphene sheet into ribbons, the closed circular dispersion of graphene plasmons is opened to become hyperbolic one. When a drift current is applied to a graphene ribbon, this hyperbolic model would evolve into the extremely asymmetric shape, which has never been noted in the noncontact heat exchanges at nanoscale before. Combining the analysis of dispersion distribution, we find that as the drift velocity increases, the hyperbolic mode exhibits more significant asymmetric characteristics. It is also found that under a larger gap size, the enhanced effect of NHSPPs on NFRHT can be weakened. In addition, the coupling effect of grating and drift current is investigated simultaneously. By changing the chemical potential and graphene filling factor, the positions and intensities of the modes can be modulated, and hence the NFRHT can be tuned accordingly. Finally, we have found that thanks to the nonreciprocal hyperbolic topology of the system, at a large twisted angle, the system with a large drift current velocity is more preferable to modulate the NFRHT compared with the zero-current case. In summary, the findings may open a promising pathway for highly efficient thermal management, energy harvesting, and subwavelength thermal imaging.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"24 1","pages":"168 - 183"},"PeriodicalIF":4.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2020.1845884","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46621220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2020-10-01DOI: 10.1080/15567265.2020.1836095
W. Cheng, A. Alkurdi, P. Chapuis
ABSTRACT Phonon heat conduction has to be described by the Boltzmann transport equation (BTE) when sizes or sources are comparable to or smaller than the phonon mean free paths (MFPs). When domains much larger than MFPs are to be treated or when regions with large and small MFPs coexist, the computation time associated with full BTE treatment becomes large, calling for a multiscale strategy to describe the total domain and decreasing the computation time. Here, we describe an iterative method to couple the BTE, under the Equation of Phonon Radiative Transfer approximation solved by means of the deterministic Discrete Ordinate Method, to a Finite-Element Modeling commercial solver of the heat equation. Small-size elements are embedded in domains where the BTE is solved, and the BTE domains are connected to a domain where large-size elements are located and where the heat equation is applied. It is found that an overlapping zone between the two types of domains is required for convergence, and the accuracy is analyzed as a function of the size of the BTE domain. Conditions for fast convergence are discussed, leading to the computation time being divided by more than five on a study case in 2D Cartesian geometry. The simple method could be generalized to other types of solvers of the Boltzmann and heat equations.
{"title":"Coupling Mesoscopic Boltzmann Transport Equation and Macroscopic Heat Diffusion Equation for Multiscale Phonon Heat Conduction","authors":"W. Cheng, A. Alkurdi, P. Chapuis","doi":"10.1080/15567265.2020.1836095","DOIUrl":"https://doi.org/10.1080/15567265.2020.1836095","url":null,"abstract":"ABSTRACT Phonon heat conduction has to be described by the Boltzmann transport equation (BTE) when sizes or sources are comparable to or smaller than the phonon mean free paths (MFPs). When domains much larger than MFPs are to be treated or when regions with large and small MFPs coexist, the computation time associated with full BTE treatment becomes large, calling for a multiscale strategy to describe the total domain and decreasing the computation time. Here, we describe an iterative method to couple the BTE, under the Equation of Phonon Radiative Transfer approximation solved by means of the deterministic Discrete Ordinate Method, to a Finite-Element Modeling commercial solver of the heat equation. Small-size elements are embedded in domains where the BTE is solved, and the BTE domains are connected to a domain where large-size elements are located and where the heat equation is applied. It is found that an overlapping zone between the two types of domains is required for convergence, and the accuracy is analyzed as a function of the size of the BTE domain. Conditions for fast convergence are discussed, leading to the computation time being divided by more than five on a study case in 2D Cartesian geometry. The simple method could be generalized to other types of solvers of the Boltzmann and heat equations.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"24 1","pages":"150 - 167"},"PeriodicalIF":4.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2020.1836095","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46267250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2020-08-19DOI: 10.1080/15567265.2020.1807662
W. Shen, Diego Vaca, Satish Kumar
ABSTRACT Frequency-domain thermoreflectance (FDTR) is a popular technique to investigate thermal properties of bulk and thin film materials. The FDTR data analysis involves fitting experimental data to a theoretical model whose accuracy may be affected by improper fitting approach and by convergence to local minima. This work proposes a novel data analysis approach using deep learning techniques. The developed deep learning model for FDTR (DL-FDTR) can accurately predict thermal conductivity, volumetric heat capacity and thermal boundary conductance with mean error below 5% for bulk samples coated with Au. DL-FDTR predictions can serve as an initial guess to the traditional fitting algorithms and can efficiently avoid local minima with regular fitting options, therefore improving the accuracy of data fitting and uncertainty evaluation.
{"title":"Reconsidering Uncertainty from Frequency Domain Thermoreflectance Measurement and Novel Data Analysis by Deep Learning","authors":"W. Shen, Diego Vaca, Satish Kumar","doi":"10.1080/15567265.2020.1807662","DOIUrl":"https://doi.org/10.1080/15567265.2020.1807662","url":null,"abstract":"ABSTRACT Frequency-domain thermoreflectance (FDTR) is a popular technique to investigate thermal properties of bulk and thin film materials. The FDTR data analysis involves fitting experimental data to a theoretical model whose accuracy may be affected by improper fitting approach and by convergence to local minima. This work proposes a novel data analysis approach using deep learning techniques. The developed deep learning model for FDTR (DL-FDTR) can accurately predict thermal conductivity, volumetric heat capacity and thermal boundary conductance with mean error below 5% for bulk samples coated with Au. DL-FDTR predictions can serve as an initial guess to the traditional fitting algorithms and can efficiently avoid local minima with regular fitting options, therefore improving the accuracy of data fitting and uncertainty evaluation.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"24 1","pages":"138 - 149"},"PeriodicalIF":4.1,"publicationDate":"2020-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2020.1807662","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43822661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2020-08-12DOI: 10.1080/15567265.2020.1806968
J. Tompkins, D. Huitink
ABSTRACT This study examines the effects of nanoparticle concentration, magnetic field frequency, and carrier fluid viscosity on the induction heating response of nanofluids exposed to an alternating magnetic field. Uncapped iron-oxide nanoparticles with a mean diameter 14.42 nm were sonically dispersed into mixtures of deionized water and ethylene glycol (WEG) as well as highly viscous oil blends. The resulting nanofluids were exposed to an alternating magnetic field with a strength of 72.6 kA/m at frequencies of 217, 303, and 397 kHz with the heating response characterized calorimetrically through the specific absorption rate (SAR). Concentration and frequency effects mirror those found in literature with SAR reduction and enhancement, respectively. Additionally, SAR output is characterized across a wide range of viscosities showing a consistent decrease in heating output as viscosity increases through the WEG regime, however, the SAR was found to be relatively consistent across the oil blends. The effects of particle aggregation were measured through dynamic light scattering denoting particle clustering as a function of viscosity. Viscosity trends with SAR are accounted for by the viscous inhibition of particles reducing their Brownian heating, as well as clustering effects potentially inhibiting heat production in the low viscosity range where aggregation is pronounced. Lastly, a model predicting the Brownian contribution to heating as a function of frequency, concentration, and viscosity is proposed. This study provides a broad view of the effects on heating output for suspensions of commercially available iron oxide nanoparticles for several concentrations and field frequencies across an expansive range of viscosity.
{"title":"Induction heating response of iron oxide nanoparticles in varyingly viscous mediums with prediction of brownian heating contribution","authors":"J. Tompkins, D. Huitink","doi":"10.1080/15567265.2020.1806968","DOIUrl":"https://doi.org/10.1080/15567265.2020.1806968","url":null,"abstract":"ABSTRACT This study examines the effects of nanoparticle concentration, magnetic field frequency, and carrier fluid viscosity on the induction heating response of nanofluids exposed to an alternating magnetic field. Uncapped iron-oxide nanoparticles with a mean diameter 14.42 nm were sonically dispersed into mixtures of deionized water and ethylene glycol (WEG) as well as highly viscous oil blends. The resulting nanofluids were exposed to an alternating magnetic field with a strength of 72.6 kA/m at frequencies of 217, 303, and 397 kHz with the heating response characterized calorimetrically through the specific absorption rate (SAR). Concentration and frequency effects mirror those found in literature with SAR reduction and enhancement, respectively. Additionally, SAR output is characterized across a wide range of viscosities showing a consistent decrease in heating output as viscosity increases through the WEG regime, however, the SAR was found to be relatively consistent across the oil blends. The effects of particle aggregation were measured through dynamic light scattering denoting particle clustering as a function of viscosity. Viscosity trends with SAR are accounted for by the viscous inhibition of particles reducing their Brownian heating, as well as clustering effects potentially inhibiting heat production in the low viscosity range where aggregation is pronounced. Lastly, a model predicting the Brownian contribution to heating as a function of frequency, concentration, and viscosity is proposed. This study provides a broad view of the effects on heating output for suspensions of commercially available iron oxide nanoparticles for several concentrations and field frequencies across an expansive range of viscosity.","PeriodicalId":49784,"journal":{"name":"Nanoscale and Microscale Thermophysical Engineering","volume":"24 1","pages":"123 - 137"},"PeriodicalIF":4.1,"publicationDate":"2020-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/15567265.2020.1806968","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48610766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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