Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy.By improving control over the heat dissipating from the human body,personal thermal...Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy.By improving control over the heat dissipating from the human body,personal thermal management can provide effective personal cooling and warming.Here,we propose a facile surface modification approach to tailor the thermal conduction and radiation properties based on commercially available fabrics,to realize better management of the whole heat transport pathway from the human body to the ambient.A bifunctional asymmetric fabric(BAF)offering both a cooling and a warming effect is demonstrated.Due to the advantages of roughness asymmetry and surface modification,the BAF demonstrates an effective cooling effect through enhanced heat conduction and radiation in the cooling mode;in the warming mode,heat dissipation along both routes is reduced for personal warming.As a result,a 4.6℃ skin temperature difference is measured between the cooling and warming BAF modes,indicating that the thermal comfort zone of the human body can be enlarged with one piece of BAF clothing.We expect this work to present new insights for the design of personal thermal management textiles as well as a novel solution for the facile modification of available fabrics for both personal cooling and warming.展开更多
In this article, a numerical model combining conduction and radiation is developed based on two flux approximation to predict the heat transfer behavior of fibrous insulation used in thermal protection systems. Monte ...In this article, a numerical model combining conduction and radiation is developed based on two flux approximation to predict the heat transfer behavior of fibrous insulation used in thermal protection systems. Monte Carlo method is utilized to determine the modified radiative properties with experimentally measured transient external temperature as high as 1 000 K. It is found that the estimated radiative properties become time-independent after about t = 3 000 s. By comparing the predicted to the measured results in transient state, the contact resistance exerts significant influences upon the temperature distribution in the specimen. Results show that the averaged absolute deviation is 3.25% when contact resistance is neglected in heat transfer model, while 1.82% with no contact resistance.展开更多
The thermal radiation of micron-sized condensed phase particles plays a dominant role during the heat transfer process in aluminized Solid Rocket Motors(SRMs).Open research mainly focuses on the radiative properties o...The thermal radiation of micron-sized condensed phase particles plays a dominant role during the heat transfer process in aluminized Solid Rocket Motors(SRMs).Open research mainly focuses on the radiative properties of alumina particles while the study considering the presence of aluminum is lacking.In addition,the thermal radiation inside the SRM with consideration of the participating particles is seldom studied.In this work,the multiscale method of predicting the thermal environment inside SRMs is established from the particle radiation at microscale to the twophase flow and heat transfer at macroscale.The effective gray radiative properties of individual particles(alumina,aluminum,and hybrid alumina/aluminum)and particles cloud are investigated with the Mie theory and approximate method.Then a numerical method for predicting the thermal environment inside SRMs with considering particle radiation is established and applied in a subscale motor.The convective and radiative heat flux distributions along inner wall of motor are obtained,and it is found that the heat transfer in the combustion chamber is dominated by thermal radiation and the radiative heat flux is essentially a constant of 5.6–6.8 MW/m^(2).The convective heat transfer plays a dominant role in the nozzle and the heat flux reaches the maximum value of 11.2 MW/m^(2) near the throat.As the combustion efficiency of aluminum drops,the radiative heat flux remains unchanged in most regions and increases slightly along the diverging section wall of the nozzle.展开更多
The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the auth...The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively.The results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude area.The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained.Under the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low altitude.It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition.It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.展开更多
Passive daytime radiative cooling(PDRC) is environment-friendly without energy input by enhancing the coating's solar reflectance(R_(solar)) and thermal emittance(ε_(LWIR)) in the atmosphere's long-wave infra...Passive daytime radiative cooling(PDRC) is environment-friendly without energy input by enhancing the coating's solar reflectance(R_(solar)) and thermal emittance(ε_(LWIR)) in the atmosphere's long-wave infrared transmission window.However,high R_(solar) is usually achieved by increasing the coating's thickness,which not only increases materials' cost but also impairs heat transfer.Additionally,the desired high R_(solar) is vulnerable to dust pollution in the outdoors.In this work,a thin paint was designed by mixing hBN plates,PFOTS,and IPA. R_(solar)=0.963 and ε_(LWIR)=0.927 was achieved at a thickness of 150 μm due to the high backscattering ability of scatters.A high through-plane thermal conductivity(~1.82 W m^(-1) K^(-1)) also can be obtained.In addition,the porous structure coupled with the binder PFOTS resulted in a contact angle of 154°,demonstrating excellent durability under dust contamination.Outdoor experiments showed that the thin paint can obtain a 2.3℃ lower temperature for sub-ambient cooling than the reference PDRC coating in the daytime.Furtherly,the above-ambient heat dissipation performance can be enhanced by spraying the thin paint on a 3D heat sink,which was 15.7℃ lower than the reference 1D structure,demonstrating excellent performance for durable and scalable PDRC applications.展开更多
Near-field thermophotovoltaic(NTPV)devices comprising a SiC-hBN-graphene emitter and a graphene-InSb cell with gratings are designed to enhance the performance of the NTPV systems.Fluctuational electrodynamics and rig...Near-field thermophotovoltaic(NTPV)devices comprising a SiC-hBN-graphene emitter and a graphene-InSb cell with gratings are designed to enhance the performance of the NTPV systems.Fluctuational electrodynamics and rigorous coupled-wave analysis are employed to calculate radiative heat transfer fluxes.It is found that the NTPV systems with two graphene ribbons perform better due to the graphene strong coupling effects.The effects of graphene chemical potential are discussed.It is demonstrated that near-field radiative heat transfer of thermophotovoltaic devices is enhanced by the coupling of surface plasmon polaritons,surface phonon polaritons,hyperbolic phonon polaritons,and magnetic polaritons caused by the graphene strong coupling effects.Rabi splitting frequency of different polaritons is calculated to quantify the mutual interaction of graphene strong coupling effects.Finally,the effects of cell grating filling ratio are investigated.The excitation of magnetic polaritons is affected by the graphene ribbon and the cell filling ratio.This investigation provides a new explanation of the enhancement mechanism of graphene-assisted thermophotovoltaic systems and a novel approach for improving the output power of the near-field thermophotovoltaic system.展开更多
Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional path...Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation.展开更多
Weyl semimetals(WSMs)have recently attracted considerable research attention because of their remarkable optical and electrical properties.In this study,we investigate the near-field radiative heat transfer(NFRHT)betw...Weyl semimetals(WSMs)have recently attracted considerable research attention because of their remarkable optical and electrical properties.In this study,we investigate the near-field radiative heat transfer(NFRHT)between graphene-covered Weyl slabs,particularly focusing on the supported coupled surface plasmon polaritons(SPPs).Unlike bare Weyl slabs where the epsilon-near-zero(ENZ)effect contributes the most to the NFRHT,adding a monolayer graphene sheet yields coupled SPPs,i.e.,the coupling of graphene SPPs(GSPPs)and Weyl SPPs(WSPPs),which dominates the NFRHT.The graphene sheet greatly suppresses the ENZ effect by compressing the parallel wavevector,thereby enabling the heat transfer coefficient(HTC)to be significantly changed.Further,for the graphene-covered magnetic Weyl slab configuration,an increase in the number of Weyl nodes suppresses the SPP coupling and ENZ effect,thereby weakening the NFRHT with a regulation ratio of 4.4 whereas an increase in the Fermi level slightly influences the NFRHT.Several typical heterostructures are also proposed for comparison,and results show that a mono-cell structure has the largest total HTC.Our findings will facilitate the understanding of surface plasmon-coupled radiative heat transfer and enable opportunities in energy harvesting and thermal management at the nanoscale based on WSM-based systems.展开更多
The increasing demand for versatile and high-quality near-field radiative heat transfer(NFRHT) has created a critical need for a design approach that can handle numerous candidate structures. In this work, we employ a...The increasing demand for versatile and high-quality near-field radiative heat transfer(NFRHT) has created a critical need for a design approach that can handle numerous candidate structures. In this work, we employ and develop an adaptive hybrid Bayesian optimization(AHBO) algorithm to design the high-quality quasi-monochromatic NFRHT. The candidate materials include hexagonal boron nitride, silicon carbide, and doped silicon. The high-quality quasi-monochromatic NFRHT is optimized over 1.0 × 10^(8) candidate structures to maximize the evaluation factor. It is worth noting that only 2.6% of the candidate structures needed to be calculated to identify the optimal structure. The optimal structure of quasi-monochromatic NFRHT is an aperiodic multilayer metamaterial that differs from conventional periodic multilayer structures. Moreover, we investigate the robustness and mechanisms of the optimal quasi-monochromatic NFRHT with respect to the vacuum gap distance and the temperature difference between the emitter and receiver. In addition, the high-quality multi-peak NFRHT is designed using the AHBO algorithm by improving the definition of the evaluation factor. The results demonstrate that the AHBO algorithm is efficient in designing high-quality quasi-monochromatic and multi-peak NFRHT, and it can be further expanded to other structural designs in the field of energy conversion.展开更多
Core-shell nanoparticles(CSNPs)are widely used in energy harvesting,conversion,and thermal management due to the excellent physical properties of different components.Because of the synergistic interaction between the...Core-shell nanoparticles(CSNPs)are widely used in energy harvesting,conversion,and thermal management due to the excellent physical properties of different components.Because of the synergistic interaction between the core and the shell,the thermal radiative properties are expected to be further enhanced.In this work,we achieve near-field radiative heat transfer(NFRHT)enhancement between SiC@Drude CSNPs.Numerical results show that the total heat flux between NPs is 1.47 times and 9.98 times higher than homogeneous SiC and Drude NPs at the same radius when the core volume fraction is 0.76.Surface modes hybridization arising from the interfaces of the shell-core and shell-air contributes to the improved thermal radiation.The effect of shift frequency on the NFRHT between SiC@Drude CSNPs is studied,showing that the enhancement ratio of NFRHT between CSNPs can reach 4.34 at a shift frequency of 1×10^(14) rad/s,which is 38.34 times higher than the previous work.This study demonstrates that surface modes hybridization in CSNPs can significantly improve NFRHT and open a novel path for high-efficiency energy transport at the nanoscale.展开更多
In this study, a novel model of photothermal conversion in a direct absorption solar collector based on the Monte Carlo and finite volume methods was built and validated and the temperatures of the novel and tradition...In this study, a novel model of photothermal conversion in a direct absorption solar collector based on the Monte Carlo and finite volume methods was built and validated and the temperatures of the novel and traditional solar collectors were compared. The sensitivity of the parameters to the radiative heat loss was investigated. Finally, the radiative heat transfer characteristics were discussed using the radiative exchange factor. The results of this study validated the advantages of the novel solar collector at both the surface and fluid temperatures. Under the conditions used in this study, the maximum temperature difference of the novel solar collector was 30 K, compared with 193 K for the traditional solar collector. Furthermore, the collector was divided into several units along the flow direction. The radiative exchange factor indicated that with an increase in the attenuation coefficient, the percentage of radiation intensity in the total solar radiation absorbed by the corresponding unit increased.Simultaneously, it decreased with an increase in the incident angle and scattering albedo. These results provide a reference for addressing the low efficiency and thermal damage caused by traditional solar collectors at high temperatures.展开更多
The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engi...The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engine combustor.The radiative transfer equation is solved by the finite volume method.The particle size is assumed to obey uniform distribution and logarithmic normal(L-N)distribution,respectively.Results reveal that when particle size obeys uniform distribution,increasing particle size with total particle volume fraction fvunchanged will result in the decreasing of the absolute value of radiative heat transfer properties,and the effect of ignoring particle scattering will also be weakened.Opposite conclusions can be obtained when total particle number concentration N0 is unchanged.Moreover,if particle size obeys L-N distribution,increasing the narrowness indexσor decreasing the characteristic diameter Dˉwith the total particle volume fraction fvunchanged will increase the absolute value of radiative heat transfer properties.With total particle number concentration N0 unchanged,opposite conclusions for radiative heat source and incident radiation terms can be obtained except for radiative heat flux term.As a whole,the effects of particle size on the radiative heat transfer in the high-temperature homogeneous gas-particle mixtures are complicated,and the particle scattering cannot be ignoring just according to the particle size.展开更多
In the post-Moore era, as the energy consumption of micro-nano electronic devices rapidly increases, near-field radiative heat transfer(NFRHT) with super-Planckian phenomena has gradually shown great potential for app...In the post-Moore era, as the energy consumption of micro-nano electronic devices rapidly increases, near-field radiative heat transfer(NFRHT) with super-Planckian phenomena has gradually shown great potential for applications in efficient and ultrafast thermal modulation and energy conversion. Recently, hyperbolic materials, an important class of anisotropic materials with hyperbolic isofrequency contours, have been intensively investigated. As an exotic optical platform, hyperbolic materials bring tremendous new opportunities for NFRHT from theoretical advances to experimental designs. To date, there have been considerable achievements in NFRHT for hyperbolic materials, which range from the establishment of different unprecedented heat transport phenomena to various potential applications. This review concisely introduces the basic physics of NFRHT for hyperbolic materials, lays out the theoretical methods to address NFRHT for hyperbolic materials, and highlights unique behaviors as realized in different hyperbolic materials and the resulting applications. Finally, key challenges and opportunities of the NFRHT for hyperbolic materials in terms of fundamental physics, experimental validations, and potential applications are outlined and discussed.展开更多
文摘Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy.By improving control over the heat dissipating from the human body,personal thermal management can provide effective personal cooling and warming.Here,we propose a facile surface modification approach to tailor the thermal conduction and radiation properties based on commercially available fabrics,to realize better management of the whole heat transport pathway from the human body to the ambient.A bifunctional asymmetric fabric(BAF)offering both a cooling and a warming effect is demonstrated.Due to the advantages of roughness asymmetry and surface modification,the BAF demonstrates an effective cooling effect through enhanced heat conduction and radiation in the cooling mode;in the warming mode,heat dissipation along both routes is reduced for personal warming.As a result,a 4.6℃ skin temperature difference is measured between the cooling and warming BAF modes,indicating that the thermal comfort zone of the human body can be enlarged with one piece of BAF clothing.We expect this work to present new insights for the design of personal thermal management textiles as well as a novel solution for the facile modification of available fabrics for both personal cooling and warming.
基金National High-tech Research and Development Program(2006AA705317)
文摘In this article, a numerical model combining conduction and radiation is developed based on two flux approximation to predict the heat transfer behavior of fibrous insulation used in thermal protection systems. Monte Carlo method is utilized to determine the modified radiative properties with experimentally measured transient external temperature as high as 1 000 K. It is found that the estimated radiative properties become time-independent after about t = 3 000 s. By comparing the predicted to the measured results in transient state, the contact resistance exerts significant influences upon the temperature distribution in the specimen. Results show that the averaged absolute deviation is 3.25% when contact resistance is neglected in heat transfer model, while 1.82% with no contact resistance.
基金supported by the Innovative Talents Support Plan of China Postdoctoral Foundation(No.BX20180244)National Natural Science Foundation of China(No.51825604)the Fundamental Research Funds for the Central Universities of China(No.xjj2018029)。
文摘The thermal radiation of micron-sized condensed phase particles plays a dominant role during the heat transfer process in aluminized Solid Rocket Motors(SRMs).Open research mainly focuses on the radiative properties of alumina particles while the study considering the presence of aluminum is lacking.In addition,the thermal radiation inside the SRM with consideration of the participating particles is seldom studied.In this work,the multiscale method of predicting the thermal environment inside SRMs is established from the particle radiation at microscale to the twophase flow and heat transfer at macroscale.The effective gray radiative properties of individual particles(alumina,aluminum,and hybrid alumina/aluminum)and particles cloud are investigated with the Mie theory and approximate method.Then a numerical method for predicting the thermal environment inside SRMs with considering particle radiation is established and applied in a subscale motor.The convective and radiative heat flux distributions along inner wall of motor are obtained,and it is found that the heat transfer in the combustion chamber is dominated by thermal radiation and the radiative heat flux is essentially a constant of 5.6–6.8 MW/m^(2).The convective heat transfer plays a dominant role in the nozzle and the heat flux reaches the maximum value of 11.2 MW/m^(2) near the throat.As the combustion efficiency of aluminum drops,the radiative heat flux remains unchanged in most regions and increases slightly along the diverging section wall of the nozzle.
基金supported by the National Natural Science Foundation of China(52078314)。
文摘The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively.The results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude area.The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained.Under the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low altitude.It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition.It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.
基金financially supported by the Natural Science Foundation of Hunan Province(Grant No.2021JJ40732)the Central South University Innovation-Driven Research Programme(Grant No.2023CXQD012)。
文摘Passive daytime radiative cooling(PDRC) is environment-friendly without energy input by enhancing the coating's solar reflectance(R_(solar)) and thermal emittance(ε_(LWIR)) in the atmosphere's long-wave infrared transmission window.However,high R_(solar) is usually achieved by increasing the coating's thickness,which not only increases materials' cost but also impairs heat transfer.Additionally,the desired high R_(solar) is vulnerable to dust pollution in the outdoors.In this work,a thin paint was designed by mixing hBN plates,PFOTS,and IPA. R_(solar)=0.963 and ε_(LWIR)=0.927 was achieved at a thickness of 150 μm due to the high backscattering ability of scatters.A high through-plane thermal conductivity(~1.82 W m^(-1) K^(-1)) also can be obtained.In addition,the porous structure coupled with the binder PFOTS resulted in a contact angle of 154°,demonstrating excellent durability under dust contamination.Outdoor experiments showed that the thin paint can obtain a 2.3℃ lower temperature for sub-ambient cooling than the reference PDRC coating in the daytime.Furtherly,the above-ambient heat dissipation performance can be enhanced by spraying the thin paint on a 3D heat sink,which was 15.7℃ lower than the reference 1D structure,demonstrating excellent performance for durable and scalable PDRC applications.
基金supported by the National Natural Science Foundation of China(Grant No.52276075)sponsored by the Natural Science Foundation of Shanghai(Grant No.21ZR1433500)。
文摘Near-field thermophotovoltaic(NTPV)devices comprising a SiC-hBN-graphene emitter and a graphene-InSb cell with gratings are designed to enhance the performance of the NTPV systems.Fluctuational electrodynamics and rigorous coupled-wave analysis are employed to calculate radiative heat transfer fluxes.It is found that the NTPV systems with two graphene ribbons perform better due to the graphene strong coupling effects.The effects of graphene chemical potential are discussed.It is demonstrated that near-field radiative heat transfer of thermophotovoltaic devices is enhanced by the coupling of surface plasmon polaritons,surface phonon polaritons,hyperbolic phonon polaritons,and magnetic polaritons caused by the graphene strong coupling effects.Rabi splitting frequency of different polaritons is calculated to quantify the mutual interaction of graphene strong coupling effects.Finally,the effects of cell grating filling ratio are investigated.The excitation of magnetic polaritons is affected by the graphene ribbon and the cell filling ratio.This investigation provides a new explanation of the enhancement mechanism of graphene-assisted thermophotovoltaic systems and a novel approach for improving the output power of the near-field thermophotovoltaic system.
基金Project supported by the National Natural Science Foundation of China (Grant No.52106099)the Natural Science Foundation of Shandong Province (Grant No.ZR2022YQ57)the Taishan Scholars Program。
文摘Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation.
基金supported by the Startup Program at Wuhan Institute of Technology(Grant No.K2021026)the Open Foundation of State Key Laboratory of Coal Combustion(Grant No.FSKLCCA2303)。
文摘Weyl semimetals(WSMs)have recently attracted considerable research attention because of their remarkable optical and electrical properties.In this study,we investigate the near-field radiative heat transfer(NFRHT)between graphene-covered Weyl slabs,particularly focusing on the supported coupled surface plasmon polaritons(SPPs).Unlike bare Weyl slabs where the epsilon-near-zero(ENZ)effect contributes the most to the NFRHT,adding a monolayer graphene sheet yields coupled SPPs,i.e.,the coupling of graphene SPPs(GSPPs)and Weyl SPPs(WSPPs),which dominates the NFRHT.The graphene sheet greatly suppresses the ENZ effect by compressing the parallel wavevector,thereby enabling the heat transfer coefficient(HTC)to be significantly changed.Further,for the graphene-covered magnetic Weyl slab configuration,an increase in the number of Weyl nodes suppresses the SPP coupling and ENZ effect,thereby weakening the NFRHT with a regulation ratio of 4.4 whereas an increase in the Fermi level slightly influences the NFRHT.Several typical heterostructures are also proposed for comparison,and results show that a mono-cell structure has the largest total HTC.Our findings will facilitate the understanding of surface plasmon-coupled radiative heat transfer and enable opportunities in energy harvesting and thermal management at the nanoscale based on WSM-based systems.
基金supported by the National Natural Science Foundation of China (Grant Nos. 52120105009 and 51906144)the Science and Technology Commission of Shanghai Municipality (Grant Nos. 20JC1414800 and 22ZR1432900)the Open Fund of Key Laboratory of Thermal Management and Energy Utilization of Aircraft of Ministry of Industry and Information Technology (Grant No. CEPE2020015)。
文摘The increasing demand for versatile and high-quality near-field radiative heat transfer(NFRHT) has created a critical need for a design approach that can handle numerous candidate structures. In this work, we employ and develop an adaptive hybrid Bayesian optimization(AHBO) algorithm to design the high-quality quasi-monochromatic NFRHT. The candidate materials include hexagonal boron nitride, silicon carbide, and doped silicon. The high-quality quasi-monochromatic NFRHT is optimized over 1.0 × 10^(8) candidate structures to maximize the evaluation factor. It is worth noting that only 2.6% of the candidate structures needed to be calculated to identify the optimal structure. The optimal structure of quasi-monochromatic NFRHT is an aperiodic multilayer metamaterial that differs from conventional periodic multilayer structures. Moreover, we investigate the robustness and mechanisms of the optimal quasi-monochromatic NFRHT with respect to the vacuum gap distance and the temperature difference between the emitter and receiver. In addition, the high-quality multi-peak NFRHT is designed using the AHBO algorithm by improving the definition of the evaluation factor. The results demonstrate that the AHBO algorithm is efficient in designing high-quality quasi-monochromatic and multi-peak NFRHT, and it can be further expanded to other structural designs in the field of energy conversion.
基金supported by the National Natural Science Foundation of China(52106099,51976173)the Shandong Provincial Natural Science Foundation(ZR2022YQ57)+3 种基金the Taishan Scholars Program,the Jiangsu Provincial Natural Science Foundation(BK20201204)the Basic Research Program of Taicang(TC2019JC01)China Postdoctoral Science Foundation(2022M710122)the Fundamental Research Funds for the Central Universities(D5000210779).
文摘Core-shell nanoparticles(CSNPs)are widely used in energy harvesting,conversion,and thermal management due to the excellent physical properties of different components.Because of the synergistic interaction between the core and the shell,the thermal radiative properties are expected to be further enhanced.In this work,we achieve near-field radiative heat transfer(NFRHT)enhancement between SiC@Drude CSNPs.Numerical results show that the total heat flux between NPs is 1.47 times and 9.98 times higher than homogeneous SiC and Drude NPs at the same radius when the core volume fraction is 0.76.Surface modes hybridization arising from the interfaces of the shell-core and shell-air contributes to the improved thermal radiation.The effect of shift frequency on the NFRHT between SiC@Drude CSNPs is studied,showing that the enhancement ratio of NFRHT between CSNPs can reach 4.34 at a shift frequency of 1×10^(14) rad/s,which is 38.34 times higher than the previous work.This study demonstrates that surface modes hybridization in CSNPs can significantly improve NFRHT and open a novel path for high-efficiency energy transport at the nanoscale.
基金supported by the National Natural Science Foundation of China (Grant No. 52041601)Hebei Natural Science Foundation (Grant No. E202203156)+1 种基金Chinese Scholarship Council (Grant No. 202106120167)partly funded the research activities—Enabling cooperation of the Harbin Institute of Technology with the Technical University of Denmark。
文摘In this study, a novel model of photothermal conversion in a direct absorption solar collector based on the Monte Carlo and finite volume methods was built and validated and the temperatures of the novel and traditional solar collectors were compared. The sensitivity of the parameters to the radiative heat loss was investigated. Finally, the radiative heat transfer characteristics were discussed using the radiative exchange factor. The results of this study validated the advantages of the novel solar collector at both the surface and fluid temperatures. Under the conditions used in this study, the maximum temperature difference of the novel solar collector was 30 K, compared with 193 K for the traditional solar collector. Furthermore, the collector was divided into several units along the flow direction. The radiative exchange factor indicated that with an increase in the attenuation coefficient, the percentage of radiation intensity in the total solar radiation absorbed by the corresponding unit increased.Simultaneously, it decreased with an increase in the incident angle and scattering albedo. These results provide a reference for addressing the low efficiency and thermal damage caused by traditional solar collectors at high temperatures.
基金supported by the National Natural Science Foundation of China (No: 51806103)Jiangsu Provincial Natural Science Foundation(No: BK20170800)Open Funds of Aero-engine Thermal Environment and Structure Key Laboratory of Ministry of Industry and Information Technology (No. CEPE2018005)
文摘The weighted-sum-of-gray-gas(WSGG)model and Mie theory are applied to study the influents of particle size on the radiative transfer in high temperature homogeneous gas-particle mixtures,such as the flame in aero-engine combustor.The radiative transfer equation is solved by the finite volume method.The particle size is assumed to obey uniform distribution and logarithmic normal(L-N)distribution,respectively.Results reveal that when particle size obeys uniform distribution,increasing particle size with total particle volume fraction fvunchanged will result in the decreasing of the absolute value of radiative heat transfer properties,and the effect of ignoring particle scattering will also be weakened.Opposite conclusions can be obtained when total particle number concentration N0 is unchanged.Moreover,if particle size obeys L-N distribution,increasing the narrowness indexσor decreasing the characteristic diameter Dˉwith the total particle volume fraction fvunchanged will increase the absolute value of radiative heat transfer properties.With total particle number concentration N0 unchanged,opposite conclusions for radiative heat source and incident radiation terms can be obtained except for radiative heat flux term.As a whole,the effects of particle size on the radiative heat transfer in the high-temperature homogeneous gas-particle mixtures are complicated,and the particle scattering cannot be ignoring just according to the particle size.
基金supported by the Natural Science Foundation of Shandong Province (ZR2020LLZ004)the National Natural Science Foundation of China (Grant No.52106099),the National Natural Science Foundation of China (Grant No.52076056)the Fundamental Research Funds for the Central Universities (Grant No.AUGA5710094020)。
文摘In the post-Moore era, as the energy consumption of micro-nano electronic devices rapidly increases, near-field radiative heat transfer(NFRHT) with super-Planckian phenomena has gradually shown great potential for applications in efficient and ultrafast thermal modulation and energy conversion. Recently, hyperbolic materials, an important class of anisotropic materials with hyperbolic isofrequency contours, have been intensively investigated. As an exotic optical platform, hyperbolic materials bring tremendous new opportunities for NFRHT from theoretical advances to experimental designs. To date, there have been considerable achievements in NFRHT for hyperbolic materials, which range from the establishment of different unprecedented heat transport phenomena to various potential applications. This review concisely introduces the basic physics of NFRHT for hyperbolic materials, lays out the theoretical methods to address NFRHT for hyperbolic materials, and highlights unique behaviors as realized in different hyperbolic materials and the resulting applications. Finally, key challenges and opportunities of the NFRHT for hyperbolic materials in terms of fundamental physics, experimental validations, and potential applications are outlined and discussed.
