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.

ON MEASUREMENT OF THERMAL CONDUCTIVITY AT HIGH TEMPERATURES

1961 ◽  
Vol 39 (7) ◽  
pp. 1029-1039 ◽  
Author(s):  
M. J. Laubitz
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
High Temperatures ◽  
Mathematical Analysis ◽  
Temperature Range ◽  
Linear Heat ◽  
Flow Systems

A method is given for exact mathematical analysis of linear heat flow systems used in measuring thermal conductivity at high temperatures. It is shown that a popular version of such a system is very sensitive to the alignment of its components, which seriously limits the temperature range of its satisfactory use.

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 Investigation of Production of Nanofiber Nonwoven Fabric and its Thermal Properties

2020 ◽  
Vol 14 (2) ◽  
pp. 264-273
Author(s):  
Wei Wu ◽  
Kenichi Urabe ◽  
Toshiki Hirogaki ◽  
Eiichi Aoyama ◽  
Hiroyoshi Sota ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Thermal Characteristics ◽  
Nonwoven Fabric ◽  
Melt Blowing ◽  
One Dimensional ◽  
Manufacturing Method ◽  
Apparent Thermal Conductivity ◽  
Computational Fluid Dynamics Cfd ◽  
Lateral Heat

Nanofibers of polypropylene were produced by a modified melt-blowing method. The manufacturing method and thermal characteristics of fabricated nonwoven-fabric nanofibers were studied. Apparent thermal conductivity was measured as an evaluation of adiabatic properties, and a prediction model was developed with computational fluid dynamics (CFD) based on a one-dimensional computer-aided engineering method. In addition, we attempted to evaluate true thermal conductivity in consideration of lateral heat dissipation during measurement by thickness. Consequently, we determined the influence of the fiber diameter and thickness of the nonwoven fabric on the thermal conductivity and demonstrated that the proposed CFD model was effective for estimating the characteristics of the thermal conductivity of the nonwoven fabric.

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.

A Study on the Thermal Conductivity of Thermal Grease According to Cu-Ni Content

2021 ◽  
Vol 880 ◽  
pp. 71-76
Author(s):  
Haneul Kang ◽  
Hyunji Kim ◽  
Sunghoon Im ◽  
Jinho Yang ◽  
Sunchul Huh
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Heat Dissipation ◽  
High Efficiency ◽  
Electronic Device ◽  
Thermal Contact ◽  
Thermal Characteristics ◽  
Internal Heat ◽  
Thermal Interface Material ◽  
Thermal Grease

An increase in power consumption density is related to the internal thermal characteristics of an electronic device, and the heat dissipation of the device is directly related to the high performance and miniaturization of the device. TIM (thermal interface material) with excellent internal heat dissipation performance are mainly used to improve the heat dissipation performance of electronic devices. Recently, the need for a high-efficiency TIM with high-performance thermal conductivity and low thermal contact resistance has increased. In this study, thermal grease was prepared by mixing Cu-Ni nanopowders with silicon oil, the thermal grease was then used as a heat transfer material. Compared to silicone thermal grease, the thermal conductivity of all prepared samples was excellent. In particularly, thermal conductivity was improved by about maximum 212% compared to that of thermal silicone of thermal grease mixed with Cu-Ni powder.

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.

AN INSTRUMENT FOR MEASURING HEAT FLOW, TEMPERATURE, AND THERMAL CONDUCTIVITY IN THE LUNAR SURFACE LAYER

1970 ◽  
Author(s):  
A. E. Wechsler ◽  
E. M. Drake ◽  
F. E. Ruccia ◽  
J. E. McCullough ◽  
P. Felsenthal ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Surface Layer ◽  
Heat Flow ◽  
Lunar Surface ◽  
Flow Temperature

Evaluation of compression-recovery and thermal characteristics of multilayer bedding textiles

2020 ◽  
Vol 32 (5) ◽  
pp. 631-643
Author(s):  
Sedat Özer ◽  
Yaşar Erayman Yüksel ◽  
Yasemin Korkmaz
Keyword(s):  
Thermal Conductivity ◽  
Sleep Quality ◽  
Thermal Comfort ◽  
Sleep Duration ◽  
Human Body ◽  
Design Methodology ◽  
Thermal Characteristics ◽  
Air Permeability ◽  
Content Type ◽  
Thermal Comfort Properties

PurposeDesign of bedding textiles that contact the human body affects the sleep quality. Bedding textiles contribute to comfort sense during the sleep duration, in addition to ambient and bed microclimate. The purpose of this study is to evaluate the effects of different layer properties on the compression recovery and thermal characteristics of multilayer bedding textiles.Design/methodology/approachIn this study, woven and knitted multilayer bedding textiles were manufactured from fabric, fiber, sponge and interlining, respectively. Different sponge thickness, fiber and interlining weight were used in the layers of samples. Later, the pilling resistance, compression and recovery, air permeability and thermal conductivity of multilayer bedding textiles were investigated.FindingsThe results indicated that samples with the higher layer weight and thickness provide better compression recovery and lower air permeability properties. It was also found that knitted surfaces show the higher air permeability than the woven surfaces depending on the fabric porosity. Layer properties have insignificant effect on the thermal conductivity values.Originality/valueWhile researchers mostly focus on thermal comfort properties of garments, there are limited studies about comfort properties of bedding textiles in the literature. Furthermore, compression recovery properties of bedding textiles have also a great importance in terms of comfort. Originality of this study is that these properties were analyzed together.

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