scholarly journals Thermal Model and Countermeasures for Future Smart Glasses

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1446 ◽  
Author(s):  
Kodai Matsuhashi ◽  
Toshiki Kanamoto ◽  
Atsushi Kurokawa
Keyword(s):  
Integrated Circuits ◽  
Network Model ◽  
High Conductivity ◽  
Maximum Temperature ◽  
Heat Sources ◽  
Transfer Coefficients ◽  
Steady State Condition ◽  
Thermal Network ◽  
Smart Glasses ◽  
The Face

The market for wearable devices such as smart watches and smart glasses continues to grow rapidly. Smart glasses are attracting particular attention because they offer convenient features such as hands-free augmented reality (AR). Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health. This paper presents a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses. It is accomplished by disassembling the state by wearing smart glasses into some parts, creating the equivalent thermal resistance circuit for each part, approximating heat-generating components such as integrated circuits (ICs) to simple physical structures, setting power consumption to the heat sources, and providing heat transfer coefficients of natural convection in air. The average temperature difference between the thermal network model and a commercial thermal solver is 0.9 °C when the maximum temperature is 62 °C. Results of an experiment using the model show that the temperature of the part near the ear that directly touches the skin can be reduced by 51.4% by distributing heat sources into both sides, 11.1% by placing higher heat-generating components farther from the ear, and 65.3% in comparison with all high conductivity materials by using a combination of low thermal conductivity materials for temples and temple tips and high conductivity materials for rims.

Synthesis of CFD Analyses and Experiments in Developing a Thermal Network Model of a Simulated Heat Spreader Panel

2008 ◽  
Author(s):  
Masaru Ishizuka ◽  
Shinji Nakagawa ◽  
Tatsuro Yoshida ◽  
Wataru Nakayama
Keyword(s):  
Network Model ◽  
Thermal Environment ◽  
Thermal Characteristics ◽  
Thermal Design ◽  
Heat Sources ◽  
Heat Spreader ◽  
Thermal Network ◽  
Wide Range ◽  
Cfd Analyses ◽  
Panel Thickness

The object of the present study is a simulated heat spreader panel (80 × 100 × 0.8 mm3) which carries five distributed heat sources and a finned heat sink near one of its corners. The panel thickness is designed to minimize temperature variation over the heat sources. The panel and the wrapping insulation possess geometric and thermal characteristics commonly found in thin electronic products. Thin configuration increases the sensitivity of internal temperature to the variation of external thermal environment; that is, a significant level of uncertainties should be expected in the thermal design of such systems. The present study aims at the development of a methodology for thermal analysis of such thin systems. Uncertainties in the thermal environment demand the coverage of a wide range of relevant parameters by the analysis, and computations can be performed most efficiently with a thermal network model. To achieve the stated goal we performed CFD simulations and the experiments, and reduced the results into a thermal network model.

scholarly journals Optimization Design of Oil-Immersed Iron Core Reactor Based on the Particle Swarm Algorithm and Thermal Network Model

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Fating Yuan ◽  
Kai Lv ◽  
Bo Tang ◽  
Yue Wang ◽  
Wentao Yang ◽  
...  
Keyword(s):  
Network Model ◽  
Fluid Velocity ◽  
Particle Swarm ◽  
Optimization Method ◽  
Maximum Temperature ◽  
Design Parameters ◽  
Iron Core ◽  
Particle Swarm Algorithm ◽  
Thermal Network ◽  
Swarm Algorithm

In this paper, according to the design parameters of oil-immersed iron core reactor, the thermal network model of windings is established by the thermo-electric analogy method, and the temperature distribution of the windings can be obtained. Meanwhile, a fluid-thermal coupled finite element model is established, the temperature and fluid velocity distribution are extracted, and the simulation results show that the error coefficient of temperature is less than 3% compared with the thermal network model, so the correctness of thermal network model has been verified. Taking the metal conductor usage and loss of windings as the optimization objects, the optimization method based on the particle swarm algorithm and thermal network model is proposed, and the Pareto optimal solutions between the metal conductor usage and loss of windings are given. The optimization results show that the metal conductor usage is reduced by 23.05%, and the loss is reduced by 20.25% compared with the initial design parameters, and the maximum temperature of winding does not exceed the expected value. Thus, the objects of low metal conductor usage and loss of windings are conflicted and cannot be optimized simultaneously; the optimization method has an important guiding significance for the design of oil-immersed iron core.

scholarly journals An Improved LPTN Method for Determining the Maximum Winding Temperature of a U-Core Motor

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1566
Author(s):  
Bin Li ◽  
Liang Yan ◽  
Wenping Cao
Keyword(s):  
Heat Flux ◽  
Heat Source ◽  
Heat Dissipation ◽  
Temperature Drop ◽  
Maximum Temperature ◽  
Heat Sources ◽  
Heat Generator ◽  
Thermal Network ◽  
Lumped Parameter ◽  
Flux Change

In a traditional lumped-parameter thermal network, no distinction is made between the heat and non-heat sources, resulting in both larger heat flux and temperature drop in the uniform heat source. In this paper, an improved lumped-parameter thermal network is proposed to deal with such problems. The innovative aspect of this proposed method is that it considers the influence of heat flux change in the heat source, and then gives a half-resistance theory for the heat source to achieve the temperature drop balance. In addition, the coupling relationship between the boundary temperature and loading position of the heat generator is also added in the lumped-parameter thermal network, so as to amend the loading position and nodes’ temperature through iterations. This approach breaks the limitation of the traditional lumped-parameter thermal network: that the heat generator can only be loaded at the midpoint, which is critical to determining the maximum temperature in asymmetric heat dissipation. By adjusting the location of heat generator and thermal resistances of each branch, the accuracy of temperature prediction is further improved. A simulation and an experiment on a U-core motor show that the improved lumped-parameter thermal network not only achieves higher accuracy than the traditional one, but also determines the loading position of the heat generator well.

scholarly journals Thermal Analyses of Reactor under High-Power and High-Frequency Square Wave Voltage Based on Improved Thermal Network Model

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1342
Author(s):  
Li Shen ◽  
Fan Xie ◽  
Wenxun Xiao ◽  
Huayu Ji ◽  
Bo Zhang
Keyword(s):  
Network Model ◽  
High Power ◽  
High Frequency ◽  
Heat Transfer Analysis ◽  
Maximum Temperature ◽  
Power Electronic ◽  
Internal Temperature ◽  
Measuring Device ◽  
Square Wave ◽  
Thermal Network

In order to quickly calculate the stable temperature of a reactor driven by high-frequency and high-power pulse voltage, an improved thermal network model suitable for a reactor under this condition is established in this paper. In power electronic equipment, the maximum temperature of the reactor is usually concentrated in its internal core. Moreover, with the increasing demand of high-power density in power electronic devices, the structure design of the reactor is more compact, and the internal magnetic field will affect the accuracy of the temperature-measuring device. Therefore, it is difficult to measure the internal temperature rise of the reactor directly. However, its stable operating temperature could be analyzed by the thermal network modeling methods and heat transfer analysis tool. Therefore, a convenient and accurate thermal network model of the reactor under high-frequency and high-power square wave voltage is established by considering the equivalent thermal resistance of the winding, the three-dimensional geometrical effect of the core and the effect of the high-frequency repeated pulse stress on the thermal penetration depth. Additionally, the internal temperature of the reactor can be obtained through the external temperature in terms of the presented model. To verify the feasibility of the thermal network model, the corresponding multiphysical field finite element simulation and the reactor temperature measurement platform is built. The simulation and experimental results show that the proposed thermal network model has a high precision and fast calculation speed, and it is an effective tool for thermal analysis of the reactor.

Control Method for Cooling Fans inside Traction Battery Boxes Installed in Battery Powered EMU Based on Thermal Network Model

2020 ◽  
Vol 140 (9) ◽  
pp. 625-632
Author(s):  
Yoshiaki Taguchi ◽  
Satoshi Kadowaki ◽  
Gaku Yoshikawa ◽  
Kenji Hatakeda ◽  
Takashi Kaneko
Keyword(s):  
Network Model ◽  
Control Method ◽  
Thermal Network ◽  
Cooling Fans

Applications of CoSi2 to VLSI and ULSI

1993 ◽  
Vol 320 ◽  
Author(s):  
S. P. Murarka
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Integrated Circuits ◽  
Lattice Mismatch ◽  
Electrical Contacts ◽  
High Conductivity ◽  
Low Resistivity ◽  
Polysilicon Films ◽  
Continued Use

ABSTRACTSilicides have found application as high conductivity, high temperature, and corrosion resistance materials that form good electrical contacts to silicon and good low resistivity cladding on polysilicon films used as gate metal. Of various silicides investigated in past CoSi2 offers several advantages including lowest resistivity, self-aligned formation, low lattice mismatch with silicon, stability in presence of dopants and on SiO2, Si3N4, or Sioxynitrides, and reliability to process temperatures ≤900°C even when used in thicknesses as thin as 50-60 nm. Thus, CoSi2 has found an application in VLSI and ULSI. In this paper, the properties, formation and processing, reliability, and applicability of CoSi2 will be reviewed. It will be shown that CoSi2 is only silicide that offers properties and reliability for continued use in sub-0.25 pm VLSI and ULSI integrated circuits.

Development of Convective Heat Transfer Near Suddenly Heated, Vertically Aligned Horizontal Wires

1987 ◽  
Vol 109 (4) ◽  
pp. 912-918 ◽  
Author(s):  
J. R. Parsons ◽  
M. L. Arey
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Fluid Layer ◽  
Convective Motion ◽  
Transient Behavior ◽  
Temperature Fields ◽  
Heat Sources ◽  
Transfer Coefficients ◽  
Vertically Aligned ◽  
The Wire

Experiments have been performed which describe the transient development of natural convective flow from both a single and two vertically aligned horizontal cylindrical heat sources. The temperature of the wire heat sources was monitored with a resistance bridge arrangement while the development of the flow field was observed optically with a Mach–Zehnder interferometer. Results for the single wire show that after an initial regime where the wire temperature follows pure conductive response to a motionless fluid, two types of fluid motion will begin. The first is characterized as a local buoyancy, wherein the heated fluid adjacent to the wire begins to rise. The second is the onset of global convective motion, this being governed by the thermal stability of the fluid layer immediately above the cylinder. The interaction of these two motions is dependent on the heating rate and relative heat capacities of the cylinder and fluid, and governs whether the temperature response will exceed the steady value during the transient (overshoot). The two heat source experiments show that the merging of the two developing temperature fields is hydrodynamically stabilizing and thermally insulating. For small spacing-to-diameter ratios, the development of convective motion is delayed and the heat transfer coefficients degraded by the proximity of another heat source. For larger spacings, the transient behavior approaches that of a single isolated cylinder.

Sign in / Sign up

Export Citation Format

Share Document