Modeling of Heat Transfer in Nanoscale Multilayer Solid-State Structures

2008 ◽  
Author(s):  
Shih-Kuo Wu ◽  
Ya-Wen Chou
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Solid State ◽  
Layer Thickness ◽  
Thermoelectric Materials ◽  
Radial Direction ◽  
Dissimilar Materials ◽  
Interface Condition ◽  
Solid State Structures

Modeling of heat transfer in nanoscale multilayer solid-state structures is presented in this article to seek a potential design of thermoelectric materials. The phonon radiative heat conduction equation is used to describe the heat transport behavior in nanoscale multilayer solid-state structures and the diffuse mismatch model is utilized to simulate the interface condition between two dissimilar materials. In this paper, the thermal conductivity of thin film superlattices, nano wire superlattices and nano tube superlattices were calculated. Then, size effects on the performance of thermoelectric micro coolers were examined in detail. The results show that the effective thermal conductivity of thermoelectric materials in superlattice structures decreases as the layer thickness decreases. In addition, the thermal conductivities of nano wire and nano tube superlattices are less than that of thin film superlattices when they have the same layer thickness. It is noted that the restriction on the radial direction not only decreases the thermal conductivity in radial direction but also in axial direction. Thus, nano wire and nano tube superlattices are potential materials for high performance thermoelectric devices.

Thermal Conductivity Enhancement in a Latent Heat Storage Device

2013 ◽  
Vol 860-863 ◽  
pp. 590-593
Author(s):  
Cha Xiu Guo ◽  
Ding Bao Wang ◽  
Gao Lin Hu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Solid State ◽  
Liquid Phase ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Storage ◽  
Storage Device ◽  
Latent Heat Storage ◽  
Conductivity Enhancement

High conductivity porosity materials are proposed to enhance the phase change materials (PCM) in order to solve the problem of low conductivity of PCM in the latent heat storage device (LHSD), and two-dimensional numerical simulation is conducted to predict the performance of the PCM by CFD software. During the phase change process, the PCM is heated from the solid state to the liquid phase in the process of melting and from the liquid phase to the solid state in the solidification process. The results show that porosity materials can improve heat transfer rate effectively, but the effect of heat transfer of Al foam is superior to that of graphite foam although the heat storage capacity is almost the same for both. The heat transfer is enhanced and the solidification time of PCM is decreased since the effective thermal conductivity of composite PCM is increased.

scholarly journals Measurement of Thermal Conductivity along the Radial Direction in a Vertical Cylindrical Packed Bed

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Swaren Bedarkar ◽  
Nurni Neelakantan Viswanathan ◽  
Nidambur Bharatha Ballal
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Crucial Role ◽  
Iron Ore ◽  
Radial Direction ◽  
Thermal Response ◽  
Packed Bed ◽  
Lumped Parameter ◽  
Scientists And Engineers

Heat transfer in packed beds and their thermal response have been of great interest for scientists and engineers for the last several years, since they play a crucial role in determining design and operation of reactors. Heat transfer of a packed bed is characterised through lumped parameter, namely, effective thermal conductivity. In the present studies, experiments were performed to investigate the thermal conductivity of a packed bed in radial direction. The packed bed was formed using iron ore particles. To determine the effective thermal conductivity a new transient methodology is proposed. The results obtained were compared with the models proposed by ZBS and Kunii and Smith.

The Solid-State Electrocaloric Refrigeration With Unimorph Beam and its Analytical Model

2018 ◽  
Author(s):  
Zhimin Sun ◽  
Qing-Ming Wang ◽  
William S. Slaughter
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Solid State ◽  
Temperature Change ◽  
Analytical Model ◽  
Step Motor ◽  
Ratio Requirement ◽  
Cooling Technology ◽  
Converse Piezoelectric Effect ◽  
Transfer Direction

Electrocaloric (EC) cooling technology, which has reversible temperature change of a polarizable material in an adiabatic condition with the application and/or removal of an electric field, exhibits some great advantages for efficient solid-state refrigeration. However, many challenges still exist in EC cooling technology. One of the main challenges is how to control the heat transfer direction. Some of the reported device types require movement of EC material by step motor or fluid media by pump back and forth between heat source and heat sink for controlling heat transfer direction. The other device designs utilize thermal diodes by adjusting their thermal conductivity to control heat transfer direction. Here we report a solid-state electrocaloric refrigeration using unimorph beam structure which has temperature change due to EC effect and bending behavior due to converse piezoelectric effect. The new device design can eliminate problems of fluid medium loss, friction, high thermal conductivity ratio requirement and external system assistance, etc., existed in the previously reported EC cooling device types. An analytical model is also derived by considering multi-physical phenomenon. The model shows that the temperature change is a combinatorial result from the couplings of thermal, electric and mechanical field in the device.

Ultrafast-laser Modification of Thermoelectric Sb2Te3 Thin Films

2012 ◽  
Vol 1456 ◽  
Author(s):  
Yuwei Li ◽  
Vladimir A. Stoica ◽  
Lynn Endicott ◽  
Guoyu Wang ◽  
Huarui Sun ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Film Surface ◽  
Ultrafast Laser ◽  
Pulsed Lasers ◽  
Scan Speed ◽  
Improved Performance ◽  
Potential Use

ABSTRACTWe have modified Sb2Te3 thin film thermoelectric materials by scanning a femtosecond laser across the film surface to create track-like nanostructures. These nanotracks have widths of 50-80 nm and a periodicity of ∼ 130 nm. We show that the nanotrack morphology is highly dependent on laser fluence and scan speed. Moreover, we performed transient thermoreflectance measurements on a laser-irradiated film and found a thermal conductivity reduction of 4.5% in the nanostructured regions compared to that of the unmodified regions. These results suggest the potential use of femtosecond pulsed lasers to create nanostructured thermoelectric materials with improved performance.

scholarly journals Modelling of the 1D Convective Heat Exchange between Logs Subjected to Freezing and to Subsequent Defrosting and the Surrounding Environment/ Egydimenziós konvektív hővezetés modellezése fagyott és normál állapotú rönk és környezte között

2015 ◽  
Vol 11 (1) ◽  
pp. 77-88
Author(s):  
Nencho Deliiski ◽  
Veselin Brezin ◽  
Natalia Tumbarkova
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Radial Direction ◽  
Initial Temperature ◽  
Convective Heat Exchange ◽  
Surrounding Environment ◽  
Effective Specific Heat ◽  
The Heat Transfer Coefficient

Abstract A 1D mathematical model for the computation of the temperature on the surface of cylindrical logs, tsr, and the non-stationary temperature distribution along the radiuses of logs subjected to freezing and subsequent defrosting at convective exponentially changing boundary conditions has been suggested. The model includes mathematical descriptions of the thermal conductivity in radial direction, λr, the effective specific heat capacity, ce, and the density, ρ, of the non-frozen and frozen wood, and also of the heat transfer coefficient between the surrounding air environment and the radial direction of horizontally situated logs, αr. With the help of the model, computations have been carried out for the determination of αr, tsr, λsr, and 1D temperature distribution along the radiuses of beech logs with diameters of 0.24 m, initial temperature 20 °C, and moisture content 0.4 kg·kg-1, 0.8 kg·kg-1, and 1.2 kg·kg-1, during their freezing at -20 °C, and during subsequent thawing at 20 °C.

scholarly journals Inorganic–organic superlattice thin films for thermoelectrics

2015 ◽  
Vol 3 (40) ◽  
pp. 10349-10361 ◽  
Author(s):  
J.-P. Niemelä ◽  
A. J. Karttunen ◽  
M. Karppinen
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Electrical Transport ◽  
Molecular Layer ◽  
Organic Thin Film ◽  
Electrical Transport Properties ◽  
Molecular Layer Deposition ◽  
Layer Deposition

Nanoscale layer-engineering using the combined atomic/molecular layer deposition (ALD/MLD) technique for the fabrication of oxide–organic thin-film superlattices is an attractive way to tailor the performance of thermoelectric materials as it potentially allows us to suppress thermal conductivity without significantly hindering the electrical transport properties.

“Open structure” semiconductors: Clathrate and channel compounds for low thermal conductivity thermoelectric materials

2000 ◽  
Vol 658 ◽  
Author(s):  
George S. Nolas
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Thermal Conduction ◽  
Lattice Structure ◽  
Amorphous Semiconductors ◽  
Open Structure ◽  
Covalently Bonded ◽  
Atomic Vibrations ◽  
Covalent Nature

ABSTRACTIn a good semiconductor the electrons (or holes) propagate through the lattice structure of well ordered atoms without being scattered by the coherent vibrations of the crystal. Thus semiconductors are good conductors of electrons (or holes) and as such have given rise to modern microprocessors that are revolutionizing the way we live. In the same semiconductors the vibrations of the lattice atoms mainly carry the heat. Due to the covalent nature of the bonding in these materials the thermal conductivity is very large. These are therefore poor materials for thermoelectric applications. If the atomic vibrations, or phonons, can be localized so that the heat transfer is essentially an atom-to- atom propagation, then the thermal conduction can be drastically reduced. A semiconductor can, in principle, have the thermal conductivity of a glass. Amorphous semiconductors are of course very poor conductors of electricity therefore one does not want the electrons to propagate through a glass-like material. Instead one wants the electrons to travel as though they only “see” the well-ordered, periodic structure of a crystal while the phonons are scattered by localized disorder within the covalently bonded lattice. “Open structure” semiconductors do, in fact, exist and recent research has given rise to new thermoelectric materials.

Solid State Chemistry Approach to Advanced Thermoelectrics. Ternary and Quaternary Alkali Metal Bismuth Chalcogenides as Thermoelectric Materials

1998 ◽  
Vol 545 ◽  
Author(s):  
Mercouri G. Kanatzidis ◽  
Duck-Young Chung ◽  
Lykourgos Iordanidis ◽  
Kyoung-Shin Choi ◽  
Paul Brazis ◽  
...  
Keyword(s):  
Solid State ◽  
Alkali Metal ◽  
Charge Transport ◽  
Thermoelectric Materials ◽  
Solid State Chemistry ◽  
Exploratory Research ◽  
Next Generation ◽  
New Materials ◽  
Bismuth Chalcogenides ◽  
Solid State Structures

AbstractOur exploratory research to identify new promising candidates for next generation thermoelectric applications has produced several interesting new materials which are briefly described here. We present their compositions, solid state structures, properties and charge transport behavior. The compounds CsBi4Te6, β-K2Bi8Se13, Ba4Bi6Se13, Eu2Pb2Bi6Se13, KBi6.33S10, Eu2Pb2Bi4Se10, Ba2Pb2Bi6S13 and K1.25 Pb3.5Bi7.25Se15 are particularly noteworthy.

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