scholarly journals Giant heat transfer in the crossover regime between conduction and radiation

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Konstantin Kloppstech ◽  
Nils Könne ◽  
Svend-Age Biehs ◽  
Alejandro W. Rodriguez ◽  
Ludwig Worbes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Near Field ◽  
Black Body ◽  
Black Body Radiation ◽  
Quantitative Measurements ◽  
Atomic Spacing ◽  
Large Heat ◽  
Vacuum Gaps ◽  
Near Field Scanning

Abstract Heat is transferred by radiation between two well-separated bodies at temperatures of finite difference in vacuum. At large distances the heat transfer can be described by black body radiation, at shorter distances evanescent modes start to contribute, and at separations comparable to inter-atomic spacing the transition to heat conduction should take place. We report on quantitative measurements of the near-field mediated heat flux between a gold coated near-field scanning thermal microscope tip and a planar gold sample at nanometre distances of 0.2–7 nm. We find an extraordinary large heat flux which is more than five orders of magnitude larger than black body radiation and four orders of magnitude larger than the values predicted by conventional theory of fluctuational electrodynamics. Different theories of phonon tunnelling are not able to describe the observations in a satisfactory way. The findings demand modified or even new models of heat transfer across vacuum gaps at nanometre distances.

High-heat-flux sensor calibration using black-body radiation

Metrologia ◽  
1998 ◽  
Vol 35 (4) ◽  
pp. 501-504 ◽  
Author(s):  
A V Murthy ◽  
B K Tsai ◽  
R D Saunders
Keyword(s):  
Heat Flux ◽  
Black Body ◽  
High Heat ◽  
Black Body Radiation ◽  
Heat Flux Sensor ◽  
Sensor Calibration ◽  
High Heat Flux ◽  
Flux Sensor

Heat Transfer Characterizations of Heat Pipe in Comparison With Copper Pipe

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Chen-Ching Ting ◽  
Jing-Nang Lee ◽  
Chien-Chih Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Source ◽  
Heat Pipe ◽  
Heat Conductivity ◽  
Cooling Efficiency ◽  
Copper Pipe ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Large Heat

The article presents some significant experimental data for studying the heat transfer behavior of heat pipe, which will further help the cooling efficiency improvement of the heat pipe cooler. It is well known that the heat pipe owns the extreme large heat conductivity and is often integrated with cooling plates for CPU cooling. The heat pipe uses special heat transfer techniques to obtain extremely large heat conductivity, which are the inside liquid evaporation for heat absorption and the inside microstructural capillarity for condensation. These special techniques yield the instant heat transfer from the heat source to the remote side directly, but the special heat transfer behavior is changed due to the integration with cooling plates. The destroyed heat transfer behavior of the heat pipe causes the cooling efficiency of the heat pipe cooler to be not able to reach a predicted good value. To improve the cooling efficiency of the heat pipe cooler we recover the original heat transfer behavior of the heat pipe integrated with cooling plates. This work first built a CPU simulator in accordance with the ASTM standard for heating the heat pipe, then uses the color schlieren technique to visualize the sequent heat flux nearby the heat pipe and the infrared thermal camera for quantitative temperature measurements synchronously. The result shows that the heat flux first appears at the opposite side from the heat source and there exhibits also the highest temperature. This is different from the heat transfer behavior of the copper pipe. Another very interesting result is that the heat flux of the cooling plate nearest to the heat source is first viewed than the others, which is similar to the integration with the copper pipe.

Large Heat Transport Due to Spontaneous Gas Oscillation Induced in a Tube With Steep Temperature Gradients

1983 ◽  
Vol 105 (4) ◽  
pp. 889-894 ◽  
Author(s):  
T. Yazaki ◽  
A. Tominaga ◽  
Y. Narahara
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Helium ◽  
Heat Conductivity ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Large Heat

This paper describes experimental studies of heat transfer due to the oscillations of gas columns that are spontaneously induced in a tube with steep temperature gradients. The tube (∼3 m in length) is closed at both ends and bent into U-shaped form at the midpoint. The temperature distribution along the tube is step-functional and symmetrical with respect to the midpoint. The warm part (closed-end sides) is maintained at room temperature and the cold one is immersed in liquid helium (4.2 K). The heat transported from the warm part to the cold is estimated from the evaporation rate of liquid helium. The heat flux by the oscillations is proportional to the square of the pressure amplitude, and the effective heat conductivity can be several orders of magnitude larger than the molecular heat conductivity of gas. The experimental results are compared with the theory of the second-order heat flux proposed by Rott and are found to be in satisfactory agreement with this.

Near-Field Radiative Heat Transfer Between Mie Resonance-Based Metamaterials Made of Coated Nonmagnetic Particles

2019 ◽  
Author(s):  
Lu Lu ◽  
Jinlin Song ◽  
Kun Zhou ◽  
Qiang Cheng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Crystals ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Nematic Liquid Crystals ◽  
Near Field ◽  
Core Shell ◽  
Mie Resonance ◽  
Shell Particles

Abstract Near-field radiative heat transfer between Mie resonance-based metamaterials composed of SiC/d-Si (silicon carbide and doped silicon) core/shell particles immersed in aligned nematic liquid crystals are numerically investigated. The metamaterials composed of core/shell particles exhibit superior performances of enhanced heat transfer and obvious modulation effect when compared to that without shell. The underlying mechanism can be explained that the excitation of Fröhlich mode and epsilon-near-zero (ENZ) resonances both contribute to the total heat flux. Modulation of near-field radiative heat transfer can be realized with the host material of aligned nematic liquid crystals. The largest modulation ratio could be achieved as high as 0.45 for metamaterials composed of core/shell SiC/d-Si particles, and the corresponding heat flux is higher than other similar materials such as LiTaO3/GaSb and Ge/LiTaO3. While with the same volume filling fraction, the modulation ratio of that composed of SiC particles is only 0.2. We show that the core/shell nanoparticles dispersed liquid crystals (NDLCs) have a great potential in enhancing the near-field radiative heat transfer in both the p and s polarizations with the radii of 0.65 μm, and Mie-metamaterials are shown for the first time to modulate heat flux within sub-milliseconds.

Nanoscale Heat Transfer and Phase Transformation Surrounding Intensely Heated Nanoparticles

2009 ◽  
Author(s):  
Pawel Keblinski ◽  
Samy Merabia ◽  
Jean-Louis Barrat ◽  
Sergei Shenogin ◽  
David G. Cahil
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Extreme Temperature ◽  
Linear Response Theory ◽  
Heat Fluxes ◽  
Generic Model ◽  
Fluid Medium ◽  
Large Heat ◽  
Dynamics Simulations ◽  
Temporal Localization

Using molecular dynamics simulations and theoretical analysis we study heat flow and phase behavior at the interface between high power-density, nanoscale heat sources and an embedding fluid medium. We show that the fluid next to the nanoparticle can be heated well above its boiling point without a phase change. Under increasing nanoparticle temperature, the heat flux saturates, which is in sharp contrast with the case of flat interfaces, where a critical heat flux is observed followed by development of a vapor layer and heat flux drop. These differences in heat transfer are explained by the curvature-induced pressure close to the nanoparticle, which inhibits boiling. We observe similar behavior for water, organic fluid, as well as generic model fluid underscoring generality of the results. We will also discuss the limits of the spatial and temporal localization of extreme temperature excursions and the limits to the applicability of the linear response theory to heat transfer at extremely large heat fluxes.

Ultrasensitive Bimaterial Cantilevers Optimized for Nanowire Heat Conduction Measurement

2012 ◽  
Author(s):  
Carlo Canetta ◽  
Ning Gu ◽  
Arvind Narayanaswamy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Conduction ◽  
Silicon Nitride ◽  
Flat Plate ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Near Field ◽  
Aluminum Coating ◽  
Thermal Sensors

We have developed a microcantilever-based technique for measurement of heat conduction through individual nanowires. We fabricated silicon nitride cantilevers with nominal dimensions of length 100 μm, width 2–6 μm, and thickness 130 nm. Cantilever chips are designed with multiple cantilevers spaced at varying distances. With a reflective aluminum coating of optimized thickness, these bimaterial cantilevers can be used as ultrasensitive thermal sensors capable of measuring very small heat flux through a nanostructure fixed between two cantilevers. The ultrasensitive bimaterial cantilevers designed in this work are not limited to heat conduction measurements, but will also be useful for measuring near-field radiative heat transfer between a sphere, attached to the tip of the cantilever, and a flat plate.

Near-Field Radiative Heat Transfer under Temperature Gradients and Conductive Transfer

2017 ◽  
Vol 72 (2) ◽  
pp. 141-149
Author(s):  
Weiliang Jin ◽  
Riccardo Messina ◽  
Alejandro W. Rodriguez
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Near Field ◽  
Current Method ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Analytical Formulas ◽  
Vacuum Gaps ◽  
The Impact

AbstractWe describe a recently developed formulation of coupled conductive and radiative heat transfer (RHT) between objects separated by nanometric, vacuum gaps. Our results rely on analytical formulas of RHT between planar slabs (based on the scattering-matrix method) as well as a general formulation of RHT between arbitrarily shaped bodies (based on the fluctuating–volume current method), which fully captures the existence of temperature inhomogeneities. In particular, the impact of RHT on conduction, and vice versa, is obtained via self-consistent solutions of the Fourier heat equation and Maxwell’s equations. We show that in materials with low thermal conductivities (e.g. zinc oxides and glasses), the interplay of conduction and RHT can strongly modify heat exchange, exemplified for instance by the presence of large temperature gradients and saturating flux rates at short (nanometric) distances. More generally, we show that the ability to tailor the temperature distribution of an object can modify the behaviour of RHT with respect to gap separations, e.g. qualitatively changing the asymptotic scaling at short separations from quadratic to linear or logarithmic. Our results could be relevant to the interpretation of both past and future experimental measurements of RHT at nanometric distances.

Near-Field Radiative Heat Transfer Between Two α-MoO3 Biaxial Crystals

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Xiaohu Wu ◽  
Ceji Fu ◽  
Zhuomin M. Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
Radiative Heat Flux ◽  
Relative Rotation ◽  
Maximum Heat ◽  
Phonon Polaritons

Abstract The near-field radiative heat transfer (NFRHT) between two semi-infinite α-MoO3 biaxial crystals is investigated numerically based on the fluctuation–dissipation theorem combined with the modified 4 × 4 transfer matrix method in this paper. In the calculations, the near-field radiative heat flux (NFRHF) along each of the crystalline directions of α-MoO3 is obtained by controlling the orientation of the biaxial crystals. The results show that much larger heat flux than that between two semi-infinite hexagonal boron nitride can be achieved in the near-field regime, and the maximum heat flux is along the [001] crystalline direction. The mechanisms for the large radiative heat flux are explained as due to existence of hyperbolic phonon polaritons (HPPs) inside α-MoO3 and excitation of hyperbolic surface phonon polaritons (HSPhPs) at the vacuum/α-MoO3 interfaces. The effect of relative rotation between the emitter and the receiver on the heat flux is also investigated. It is found that the heat flux varies significantly with the relative rotation angle. The modulation contrast can be as large as two when the heat flux is along the [010] direction. We attribute the large modulation contrast mainly to the misalignment of HSPhPs and HPPs between the emitter and the receiver. Hence, the results obtained in this work may provide a promising way for manipulating near-field radiative heat transfer between anisotropic materials.

Near Field Surface Wave Enhanced Photon Transport

2003 ◽  
Author(s):  
Arvind Narayanaswamy ◽  
Gang Chen
Keyword(s):  
Energy Transfer ◽  
Near Field ◽  
Black Body ◽  
Black Body Radiation ◽  
Radiative Energy ◽  
Radiative Energy Transfer ◽  
Fluctuation Dissipation ◽  
Polar Materials ◽  
Photovoltaic Material ◽  
Classical Radiation

Radiative energy transfer as described by the classical radiation transfer theory of Planck is valid only when the distance between the participating surfaces is larger than a few wavelengths of the characteristic radiation. When the spacing is comparable to the wavelength, electromagnetic theory and the fluctuation-dissipation theorem can be used to predict the energy transfer between the surfaces. We have used the electromagnetic Green’s function method to model the thermal energy transfer between two half planes with planar layers in between. With polar materials as the half planes, we see a narrowband energy transfer in the near field due to energy transfer by surface phonon polaritons. We have used this technique to show that such a resonance, however dampened, persists even with the presence of a layer of photovoltaic material. This results in not only an increased energy transfer to the photovoltaic material as compared to black body radiation but also imparts a narrowband characteristic to it. The implications for thermophotovoltaics are discussed.

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