Thermal Spreading Performance of Copper-Graphite Film Attached on BLM-Reflector

2014 ◽  
Vol 540 ◽  
pp. 126-129
Author(s):  
Chi Chiang Lee ◽  
Hong Te Hsu ◽  
Ming Chih Huang ◽  
Hong Hsin Huang
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Temperature Increase ◽  
Heat Dissipation ◽  
Thermal Spread ◽  
Graphite Film ◽  
Performance Results

In LEDs Backlight Module, reflector who made by metal and contacts to LEDs possesses higher thermal conductivity. The reflector was expected to dissipate the heat from the LEDs, however, it is not good enough to decrease the LEDs temperature rise. In this study, a copper-graphite film with thickness of 82.5 μm was attached to the back of reflector to increase the heat dissipation. The temperatures along the x, y, and z direction were measured to evaluate the thermal spread performance. Results showed that a 19% temperature rise decrease was found for LEDs and a half temperature increase was also measured along the LEDs bar direction. In addition to that a higher thermal conductivity could spread the heat to the remote end resulting in temperature increasing to enhance the heat dissipation by way of reflector.

Effect of Gas Flow on the Temperature Rise of a Micro-Beam-Type Thermal Conductivity Detector

2013 ◽  
Author(s):  
Hiroshi Takamatsu ◽  
Kosuke Hisada ◽  
Takanobu Fukunaga ◽  
Kosaku Kurata
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Gas Flow ◽  
Heat Dissipation ◽  
Air Flow ◽  
Leading Edge ◽  
Potential Core ◽  
Mems Sensor ◽  
Beam Type ◽  
Dc Current

We have proposed a “micro-beam” MEMS sensor for measuring the thermal conductivity of gases and liquids. It is a beam-shaped metallic foil sensor, approximately 10 μm in length, that is built over a trench on a silicon substrate. The principle of the measurement is to determine the thermal conductivity of a sample from the temperature rise of the sensor at a steady state, which is achieved within a millisecond. Potential application of the sensor would be gas sensors and gas chromatography, where the sensor is exposed to a gas flow. Hence the objective of the present study is to examine the effect of flow on the temperature of the sensor. A chip with a platinum sensor fabricated on its surface was embedded in a flat PVC plate and placed in the potential core of an air flow from a nozzle. The electrical resistance of the sensor was measured by a four-wire technique with heating the sensor with DC current. The results showed that the temperature rise at a given heating rate, which indicates the heat dissipating potential to the air, did not change with increasing the air velocity. It also agreed well each other irrespective of the angle of attack or the length from the leading edge. The results demonstrated that the temperature rise of the sensor was independent of the air flow, suggesting that the heat dissipation was governed only by the heat conduction to the air.

scholarly journals Heat Dissipation and Ripple Current Rating in Electrolytic Capacitors

1975 ◽  
Vol 2 (2) ◽  
pp. 109-114 ◽  
Author(s):  
F. G. Hayatee
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Temperature Rise ◽  
Mathematical Analysis ◽  
Heat Dissipation ◽  
Thermal Characteristics ◽  
Electrolytic Capacitors ◽  
Allowable Temperature

The ripple current rating in electrolytic capacitors is limited by the maximum allowable temperature rise inside the capacitor. The temperature rise is determined by the I2R losses inside the capacitor and the efficiency of heat flow from the interior to the surrounding. The ripple current rating can be extended by either reducing the tanδof the capacitor or by increasing the efficiency of heat flow to ambient.The heat flow is determined by the thermal characteristics of the capacitor surface and thermal conductivity of the medium separating the capacitor winding from the surrounding.In this article a mathematical analysis for the heat flow in capacitors is given. The effects of various parameters are examined and methods of extending the ripple current rating are discussed.

scholarly journals Estimations on Properties of Redox Reactions to Electrical Energy and Storage Device of Thermoelectric Pipe (TEP) Using Polymeric Nanofluids

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1812
Author(s):  
Qin Gang ◽  
Rong-Tsu Wang ◽  
Jung-Chang Wang
Keyword(s):  
Thermal Conductivity ◽  
Power Density ◽  
Heat Dissipation ◽  
Electrical Energy ◽  
Steel Tube ◽  
Storage Device ◽  
Stainless Steel Tube ◽  
The Novel ◽  
Empirical Formulas ◽  
Dissipative Heat

A thermoelectric pipe (TEP) is constructed by tubular graphite electrodes, Teflon material, and stainless-steel tube containing polymeric nanofluids as electrolytes in this study. Heat dissipation and power generation (generating capacity) are both fulfilled with temperature difference via the thermal-electrochemistry and redox reaction effects of polymeric nanofluids. The notion of TEP is to recover the dissipative heat from the heat capacity generated by the relevant machine systems. The thermal conductivity and power density empirical formulas of the novel TEP were derived through the intelligent dimensional analysis with thermoelectric experiments and evaluated at temperatures between 25 and 100 °C and vacuum pressures between 400 and 760 torr. The results revealed that the polymeric nanofluids composed of titanium dioxide (TiO2) nanoparticles with 0.2 wt.% sodium hydroxide (NaOH) of the novel TEP have the best thermoelectric performance among these electrolytes, including TiO2 nanofluid, TiO2 nanofluid with 0.2 wt.% NaOH, deionized water, and seawater. Furthermore, the thermal conductivity and power density of the novel TEP are 203.1 W/(m·K) and 21.16 W/m3, respectively.

scholarly journals Study of Thermometry in Two-Dimensional Sb2Te3 from Temperature-Dependent Raman Spectroscopy

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Manavendra P. Singh ◽  
Manab Mandal ◽  
K. Sethupathi ◽  
M. S. Ramachandra Rao ◽  
Pramoda K. Nayak
Keyword(s):  
Thermal Conductivity ◽  
Raman Spectroscopy ◽  
Temperature Coefficient ◽  
Heat Dissipation ◽  
Peak Position ◽  
Two Dimensional ◽  
Phonon Modes ◽  
Temperature Dependent ◽  
Excellent Candidate ◽  
High Figure

AbstractDiscovery of two-dimensional (2D) topological insulators (TIs) demonstrates tremendous potential in the field of thermoelectric since the last decade. Here, we have synthesized 2D TI, Sb2Te3 of various thicknesses in the range 65–400 nm using mechanical exfoliation and studied temperature coefficient in the range 100–300 K using micro-Raman spectroscopy. The temperature dependence of the peak position and line width of phonon modes have been analyzed to determine the temperature coefficient, which is found to be in the order of 10–2 cm−1/K, and it decreases with a decrease in Sb2Te3 thickness. Such low-temperature coefficient would favor to achieve a high figure of merit (ZT) and pave the way to use this material as an excellent candidate for thermoelectric materials. We have estimated the thermal conductivity of Sb2Te3 flake with the thickness of 115 nm supported on 300-nm SiO2/Si substrate which is found to be ~ 10 W/m–K. The slightly higher thermal conductivity value suggests that the supporting substrate significantly affects the heat dissipation of the Sb2Te3 flake.

Thermoelectrical properties of graphene knife-coated cellulosic fabrics for defect monitoring in Joule-heated textiles

2022 ◽  
pp. 152808372110569
Author(s):  
Tamara Ruiz-Calleja ◽  
Rocío Calderón-Villajos ◽  
Marilés Bonet-Aracil ◽  
Eva Bou-Belda ◽  
Jaime Gisbert-Payá ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Increase ◽  
Low Voltage ◽  
Industrial Applications ◽  
Protective Equipment ◽  
Voltage Application ◽  
Useful Life ◽  
Coated Fabrics ◽  
Conductive Particles

Knife-coating can confer new properties on different textile substrates efficiently by integrating various compounds into the coating paste. Graphene nanoplatelets (GNP) is one of the most used elements for the functionalization of fabrics in recent years, providing electrical and thermal conductivity to fabrics, later used to develop products such as sensors or heated garments. This paper reports thermoelectrically conductive textiles fabrication through knife-coating of cellulosic fabrics with a GNP load from 0.4 to 2 wt% within an acrylic coating paste. The fabric doped with the highest GNP content reaches a temperature increase of 100°C in few seconds. Besides, it is found out that the thermographic images obtained during the electrical voltage application provide maps of irregularities in the dispersion of conductive particles of the coating and defects produced throughout their useful life. Therefore, the application of a low voltage on the coated fabrics allows fast and effective heating by Joule’s effect, whose thermographic images, in turn, can be used as structural maps to check the quality of the GNP doped coating. The temperature values and the heating rate obtained make these fabrics suitable for heating devices, anti-ice and de-ice systems, and protective equipment, which would be of great interest for industrial applications.

Orientation Specific Thermal Properties of Polyimide Film

2000 ◽  
Vol 123 (3) ◽  
pp. 273-277 ◽  
Author(s):  
Robert J. Samuels ◽  
Nancy E. Mathis
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Polyimide Film ◽  
New Materials ◽  
Polyimide Films ◽  
Nondestructive Technique ◽  
Theoretical Understanding ◽  
First Time ◽  
The Relationship ◽  
Transfer Mechanisms

The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.

Preparation and Properties of Heat-Dissipation Coating Filled with Carbon-Based Filler

2017 ◽  
Vol 898 ◽  
pp. 1532-1538
Author(s):  
Yue Gao ◽  
Qian Jin Mao ◽  
Hai Wang ◽  
Zi Ming Wang ◽  
Su Ping Cui
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Dissipation ◽  
Filler Content ◽  
Simulated Data ◽  
Content Type ◽  
Element Simulation ◽  
Method Of Solution ◽  
High Emissivity ◽  
Pure Resin

Aiming at the heat dissipation of equipment, and based on ANSYS finite element simulation of thermal conductivity of coatings, the heat-dissipation coating filled with graphite and carbon nanotubes respectively, which integrates heat conduction (high thermal conductivity) and radiation (high emissivity), was successfully prepared by the method of solution mixing. Meanwhile, the effects of filler content, type and shape on thermal conductivity and emissivity of the coating were also investigated. The results indicate that the rising tendency between the simulated data by FEM and experimental value is consistent, which has a certain directive significance. In addition, graphite can improve the thermal conductivity and emissivity of the coating effectively; however, the emissivity decreases when the content exceeds 23.08%. The carbon nanotubes can improve the thermal conductivity and emissivity simultaneously, the thermal conductivity is 2.3 times that of pure resin, and the emissivity is up to 0.91 at the 2.0% mass fraction of carbon nanotubes.

scholarly journals Thermal Analysis of AlGaN/GaN HEMTs Considering Anisotropic And Inhomogeneous Thermal Conductivity

2021 ◽  
Author(s):  
Yao Li ◽  
Zixuan Zheng ◽  
Qun Li ◽  
Hongbin Pu
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Power Dissipation ◽  
Thermal Characteristics ◽  
Maximum Temperature ◽  
Base Temperature ◽  
Initial Growth ◽  
Boltzmann Transport ◽  
Growth Interface ◽  
Anisotropic Thermal Conductivity

Abstract To examine the differences of thermal characteristics introduced by material thermal conductivity, anisotropic polycrystalline diamond (PCD) and GaN are analyzed based on the accurate model of grain sizes in the directions of parallel and vertical to the interface and an approximate solution of the phonon Boltzmann transport equation. Due to the space-variant grain structures of PCD, the inhomogeneous-anisotropic local thermal conductivity, homogeneous-anisotropic thermal conductivity averaged over the whole layer and the typical values of inhomogeneous-isotropic thermal conductivity are compared with/without anisotropic GaN thermal conductivity. The results show that the considerations of inhomogeneous-anisotropic PCD thermal conductivity and anisotropic GaN thermal conductivity are necessary for the accurate prediction of temperature rise in the GaN HEMT devices, and when ignoring both, the maximum temperature rise is undervalued by over 16 K for thermal boundary resistance (TBR) of 6.5 to 60 m2K/GW at power dissipation of 10 W/mm. Then the dependences of channel temperature on several parameters are discussed and the relations of thermal resistance with power dissipation are extracted at different base temperature. Compared with GaN, SiC and Si substrates, PCD is the most effective heat spreading layer though limited by the grain size at initial growth interface.

scholarly journals The Kirchhoff Transformation for Convective-radiative Thermal Problemsin Fins

2021 ◽  
Vol 15 ◽  
pp. 12-21
Author(s):  
Jonatas Motta Quirino ◽  
Eduardo Dias Correa ◽  
Rodolfo do Lago Sobral
Keyword(s):  
Thermal Conductivity ◽  
Boundary Conditions ◽  
Thermal Radiation ◽  
Heat Dissipation ◽  
Variable Thermal Conductivity ◽  
Dirichlet Boundary Conditions ◽  
Heat Transfer Analysis ◽  
Temperature Function ◽  
Kirchhoff Transformation ◽  
Comparison Of The Results

- The present work describes the thermal profile of a single dissipation fin, where their surfaces reject heat to the environment. The problem happens in steady state, which is, all the analysis occurs after the thermal distribution reach heat balance considering that the fin dissipates heat by conduction, convection and thermal radiation. Neumann and Dirichlet boundary conditions are established, characterizing that heat dissipation occurs only on the fin faces, in addition to predicting that the ambient temperature is homogeneous. Heat transfer analysis is performed by computational simulations using appropriate numerical methods. The most of solutions in the literature consider some simplifications as constant thermal conductivity and linear boundary conditions, this work addresses this subject. The method applied is the Kirchhoff Transformation, that uses the thermal conductivity variation to define the temperatures values, once the thermal conductivity variate as a temperature function. For the real situation approximation, this work appropriated the silicon as the fin material to consider the temperature function at each point, which makes the equation that governs the non-linear problem. Finally, the comparison of the results obtained with typical results proves that the assumptions of variable thermal conductivity and heat dissipation by thermal radiation are crucial to obtain results that are closer to reality.

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