scholarly journals Approximate formulae for thermal resistance matching of thermoelectric coolers operating at room temperature

2021 ◽  
Vol 23 ◽  
pp. 100799
Author(s):  
Jiwon Kang ◽  
Daehyun Wee ◽  
Semi Bang
Keyword(s):  
Thermal Resistance ◽  
Room Temperature ◽  
Thermoelectric Coolers

Kinetics of the Thermal Disappearance of Radicals Formed During the Radiolysis of Aspartic Acid

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Mihai Contineanu ◽  
iulia Contineanu ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Thermal Resistance ◽  
Aspartic Acid ◽  
Room Temperature ◽  
Esr Spectra ◽  
Complex Mechanism ◽  
Radical Species ◽  
Mechanisms Of Formation ◽  
Kinetics Of

The radiolysis of the isomers L-, D- and DL- of the aspartic acid, in solid polycrystalline state, was investigated at room temperature. The analysis of their ESR spectra indicated the formation of at least two radicalic entities. The radical, identified as R3, resulting from the deamination of the acid, exhibits the highest concentration and thermal resistance. Possible mechanisms of formation of three radical species are suggested, based also on literature data. The kinetics of the disappearance of radical R3 indicated a complex mechanism. Three possible variants were suggested for this mechanism.

Thermal Resistance of Fly Ash Geopolymers with Alumina as Additive

2018 ◽  
Vol 281 ◽  
pp. 182-188
Author(s):  
Yong Sing Ng ◽  
Yun Ming Liew ◽  
Cheng Yong Heah ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Kamarudin Hussin
Keyword(s):  
Elevated Temperature ◽  
Fly Ash ◽  
Thermal Resistance ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Room Temperature ◽  
Strength Degradation ◽  
Alumina Addition ◽  
Higher Temperature ◽  
Temperature Exposure

The present work investigates the effect of alumina addition on the thermal resistance of fly ash geopolymers. Fly ash geopolymers were synthesised by mixing fly ash with activator solution (A mixture of 12M sodium hydroxide and sodium silicate) at fly ash/activator ratio of 2.5 and sodium silicate/sodium hydroxide ratio of 2.5. The alumina (0, 2 and 4 wt %) was added as an additive. The geopolymers were cured at room temperature for 24 hours and 60°C for another 24 hours. After 28 days, the geopolymers was heated to elevated temperature (200 - 1000°C). For unexposed geopolymers, the addition of 2 wt % of alumina increased the compressive strength of fly ash geopolymers while the strength decreased when the content increased to 4 wt.%. The temperature-exposed geopolymers showed enhancement of strength at 200°C regardless of the alumina content. The strength reduced at higher temperature exposure (> 200°C). Despite the strength degradation at elevated temperature, the strength attained was relatively high in the range of 13 - 45 MPa up to 1000°C which adequately for application as structural materials.

Modeling of Thermoelectric Coolers for Freezing/Thawing Applications

2009 ◽  
Vol 419-420 ◽  
pp. 33-36 ◽  
Author(s):  
Rong Yuan Jou
Keyword(s):  
Thermal Resistance ◽  
Thermoelectric Device ◽  
Cold Side ◽  
Thermoelectric Coolers ◽  
Egg Shells ◽  
Thawing Processes ◽  
Design Case ◽  
Design And Application

Thermoelectric coolers are often used in freezing chuck to freeze or to thaw easy broken egg-shells, clays, and other ferrous/nonferrous materials, which are incapable to machine it by other clamping technology. For design and application purposes, detailed studies of freezing/thawing processes by thermoelectric coolers are inevitable to the success of this technology. In this study, an experiment to measure the thermal resistance of single thermoelectric device is conducted and a model to calculate its hot and cold side temperatures is derived. Moreover, a design case of freezing chuck system is analyzed by COMSOL software to investigate the freezing/thawing functions and to evaluate its effectiveness.

Washable Coatings for Packaging Processes

2016 ◽  
Vol 2016 (1) ◽  
pp. 000094-000099
Author(s):  
Alex Brewer ◽  
Alex Laymon ◽  
John Moore
Keyword(s):  
Polyvinyl Alcohol ◽  
Thermal Resistance ◽  
Room Temperature ◽  
Solder Bump ◽  
Dielectric Coating ◽  
Cross Linking ◽  
Thermal Compression ◽  
Temporary Bonding ◽  
Heat Activation ◽  
Industry Needs

Abstract Many packaging processes require the protection of components while another application is conducted. This may include a planarizing coat over large topography while a deposition, bonding, or curing step is completed. Washable coatings are materials that protect the substrate during thermal or mechanical activities and are simply washed away using readily available and green products, such as water or detergent. Washable products are not new, an example includes laser washable coatings that remove debris from the heat activation zone (HAZ) during scribe and break processes. In such cases, thermal resistance is desired as high as possible. The chemistry of washable products includes polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) [1]. While these are excellent choices for consumer packaging (e.g. laundry packets, vitamins), they are best used in electronics for room temperature processing due to their cross-linking upon exposure to heat and metals. Alternatively, thermal resistant and washable products (e.g. DaeCoat™ 515) are available that provide protection to ≥300°C without the aid of mechanical tooling [2]. Planarizing coatings over metals can be thick (>300μm) as in cases where solder bump encapsulation is needed during dielectric coating and cure or when another die is thermal compression bonded. This approach has been demonstrated with washable temporary bonding adhesives in protecting C4 bumps while bonding micro-bumped die onto FPGA interposers [3]. Washable adhesives have been created for thermal and vacuum driven processing as EMI/RFI shielding in a PVD tool. Such coatings are applied to porous substrates, affixing die, processing, and removal by water washing [4]. Success in these and related temporary applications depend upon matching the chemistry of the washable coating with the process. Our experience in creating solutions for these and other industry needs will be discussed as well as the criteria for using temporary washable coatings.

Transient and Steady State Thermal Response of a System With Thermoelectric Coolers

2017 ◽  
Author(s):  
Kayvan Abbasi ◽  
Sukhvinder Kang
Keyword(s):  
Steady State ◽  
Thermal Resistance ◽  
Time Scales ◽  
Thermoelectric Module ◽  
Thermal Response ◽  
Thermal Mass ◽  
Thermoelectric Cooler ◽  
Simple Method ◽  
Thermoelectric Coolers ◽  
Transient And Steady State

The transient and steady state response of a thermal system with thermoelectric coolers has been studied analytically. The system is comprised of a device with thermal mass inside an insulated enclosure, thermal resistance between the mass and the thermoelectric cooler, insulation thermal resistance, TIM between thermoelectric cooler layers, and a heatsink on the hot side of the thermoelectric cooler. It is assumed that the thermal mass of the thermoelectric cooler is negligible compared to other thermal masses. The analytical transient solution consists of two exponential eigen functions and hence two time scales (i.e. two eigen values). The analytical solution has been validated with a numerical Runge-Kutta solution. A simple method is explained to combine thermoelectric coolers in series and parallel. The time scales are studied for different parameters and the key parameters for time scale minimization are identified. It is found that the thermoelectric module thermal resistance limits the fastest transient response.

Heat Switch to Control the Local Thermal Resistance Using Liquid Pillar Control

2009 ◽  
Author(s):  
Su-Heon Jeong ◽  
Wataru Nakayama ◽  
Sun-Kyu Lee
Keyword(s):  
Thermal Resistance ◽  
Thermal Management ◽  
Room Temperature ◽  
Hydrophobic Surface ◽  
Specific Area ◽  
Flow Regulation ◽  
Channel State ◽  
Stop Valve ◽  
Switch Operation ◽  
Electronics Packages

This paper presents the heat switch for electronic package to be operated at room temperature. The heat switch controls the thermal resistance between two objective plates using liquid pillar. By forming the liquid pillar, the temperature of the specific area can be controlled locally. In order to realize the desired switch operation, the heat switch should be provided with reservoir, switching channel and breathing channel. The channels are carefully designed to control the liquid pillar precisely. The liquid pillar formation depends on the liquid contact angle. The designed channel geometry can generate hydrophobic surface by using suddenly diverging shape like as capillary stop valve. Thus, the liquid pillar can be created at desired point with high stability. To verify the switch operation, the switch panel was designed and experiments were performed on a designed switch for the liquid pillar control and the heat flow regulation. The experiments show that the heat switch is able to work properly. Also, the temperature distribution and thermal resistance was changed in accordance with channel state as desired. As a result, the heat switch can be a good candidate of thermal management in the commercial electronics packages.

Diamond Composites for Power Electronics Application

2008 ◽  
Vol 59 ◽  
pp. 143-147
Author(s):  
Svetlana Levchuk ◽  
Monika Poebl ◽  
Gerhard Mitic
Keyword(s):  
Thermal Resistance ◽  
Thermal Cycling ◽  
Power Electronics ◽  
Room Temperature ◽  
Thermal Loads ◽  
Diamond Composite ◽  
X Ray ◽  
Igbt Modules ◽  
Active Metal ◽  
Solder Layer

In view of power electronics applications, baseplates made from metal diamond composites have been manufactured and characterised. The surface contours of the baseplates were measured during thermal loads up to 180°C starting at room temperature with help of the TherMoiré technique. X-ray analysis investigation was performed to detect porosity and local inhomogeneities of the baseplates. Al- and Cu-based diamond composite baseplates were Ni-plated and used for manufacturing of 3.3 kV IGBT modules. The solder layer between AlN AMB (active metal brazing) substrates and baseplates was investigated by ultrasonic and X-Ray analyses. Thermal resistance of the manufactured IGBT modules was characterised and compared to that of IGBT modules with AlSiC or Cu baseplates. The influence of thermal cycling on the solder layer and thermal resistance of the manufactured module was investigated.

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