Journal of Electronics Cooling and Thermal Control

Journal Information
ISSN / EISSN : 2162-6162 / 2162-6170
Current Publisher: Hans Publishers (10.4236)
Former Publisher:
Total articles ≅ 78
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SHERPA/ROMEO
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Mamadou Kabirou Touré, Papa Momar Souaré, Julien Sylvestre
Journal of Electronics Cooling and Thermal Control, Volume 10, pp 15-33; doi:10.4236/jectc.2021.102002

Abstract:
A detailed sensitivity study was carried out on various key parameters from a high precision numerical model of a microelectronic package cooled by natural convection, to provide rules for the thermal modeling of microelectronic packages subjected to natural convection heat transfer. An accurate estimate of the junction temperature, with an error of less than 1˚C, was obtained compared to the experimental data for the vertical and horizontal orientations of the test vehicle in the JEDEC Still Air configuration. The sensitivity study showed that to have an accurate estimate of the temperature, the following elements should be present in the thermal model: radiation heat transfer in natural convection cooling; a computational fluid dynamics analysis to find realistic convection coefficients; detailed models of the high conductivity elements in the direction of the heat flow towards the environment; and finally precise values for the thicknesses of layers and the thermal properties of the substrate and the printed circuit board.
Andreas Griesinger, Christian Windel, Yungwan Kwak, Arthur Petuchow
Journal of Electronics Cooling and Thermal Control, Volume 10, pp 1-13; doi:10.4236/jectc.2021.101001

Abstract:
Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.
Mousa M. Mohamed
Journal of Electronics Cooling and Thermal Control, Volume 09, pp 23-45; doi:10.4236/jectc.2020.92002

Abstract:
The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effects on the transmission heat through outer walls, ceiling and glazing windows. Good thermal isolation for buildings is important to reduce the transmitted heat and consumed power. The buildings models are constructed from common materials with 0 - 16 cm of thermal insulation thickness in the outer walls and ceilings, and double-layers glazing windows. The building heat loads were calculated for two types of walls and ceiling with and without thermal insulation. The cooling load temperature difference method, CLTD, was used to estimate the building heat load during a 24-hour each day throughout spring, summer, autumn and winter seasons. The annual cooling degree-day, CDD was used to estimate the optimal thermal insulation thickness and payback period with including the solar radiation effect on the outer walls surfaces. The average saved energy percentage in summer, spring, autumn and winter are 35.5%, 32.8%, 33.2% and 30.7% respectively, and average yearly saved energy is about of 33.5%. The optimal thermal insulation thickness was obtained between 7 - 12 cm and payback period of 20 - 30 month for some Egyptian Cities according to the Latitude and annual degree-days.
Hasan Abbasinejad, Reza Hoseini Abardeh
Journal of Electronics Cooling and Thermal Control, Volume 09, pp 1-21; doi:10.4236/jectc.2020.91001

Abstract:
This paper aims to model a subcooled flow boiling in a vertical stainless-steel micro-channel with an upward flow in 1 mm diameter, 40 mm length and 0.325 mm thickness tube. Water has been considered as a working fluid. The heat flux varies from 600 - 750 kW·m-2, input velocity from 1 - 2 m·s-1, and the subcooled temperature varies from 59.6 - 79.6 K. The working pressure and saturation temperature are 1 atm and 372.75 K, respectively. The results show that, the flow boiling keeps the temperature of the channel wall lower and more uniform than a single-phase flow, as long as the flow boiling does not reach the dry-out point. The onset point of dry-out depends on three factors, heat flux, inlet velocity, and subcooled temperature. In addition, the dry-out occurs at a point near the channel inlet with increased heat flux and subcooled temperature. Decreasing the inlet velocity would also cause the dry-out point to shift closer to the inlet of the channel.
Zviad Kovziridze
Journal of Electronics Cooling and Thermal Control, Volume 08, pp 31-47; doi:10.4236/jectc.2018.83003

Abstract:
Goal: In the process of exploitation of ceramic composites often we encounter not only high mechanical stresses but also thermal loads and air-thermal shocks. These loads are transformed into failure/rupture stress energy, when strength of work-pieces is less than loads, which develops pluck from the crack top, resulting in destruction of objects. Considering such extreme operation conditions computation of energies which contribute to materials catastrophe seems rather interesting. Method: The formula parameters were selected on the basis of study and generalization of micro- and macro-mechanical characteristics of ceramic materials. Results: The formula covers the process of creation of energies as a result of mechanical and thermal loads affecting the work-piece and analyses of mechanisms of impact of these energies on the cracks existing in the material; results of energies affecting the existing cracks as a result of such loads and results of starting of mechanisms of spreading of energies developed inside the work piece, which lead material to the catastrophe. Conclusion: On the basis of crack development mechanisms the universal relationship of total energy of the work-piece and its mass was established considering crack developing speed under critical stress conditions. Failure stress energy formula has been offered.
Zviad Kovziridze
Journal of Electronics Cooling and Thermal Control, Volume 08, pp 49-54; doi:10.4236/jectc.2018.84004

Abstract:
Goal: Formulation of empiric formula, which establishes relations between major matrix parameters of ceramic materials and composites and the coefficient of resistance to material thermogradient. Method: Harcpurt’s method of cooling of water in boiling regime till disappearance of water. Results: It is proved that work-pieces reveal maximum thermal resistance and preservation of exploitation properties, when total closed porosity is within 2% - 8%, and pore sizes vary within 1 - 6 mcm. Besides, they are more or less of spherical form and are spread equally in the matrix. Conclusion: Thermogradient effect formula was defined for complex form work-pieces, when surfaces in the pieces are transacted several times by angles of various curvature radii.
Nooshien Laderian, Arash Daghighi
Journal of Electronics Cooling and Thermal Control, Volume 08, pp 19-30; doi:10.4236/jectc.2018.82002

Abstract:
In this paper, thermal effects and Drain Induced barrier lowering (DIBL) of silicon-on-insulator (SOI) and silicon-on-diamond (SOD) transistors with 22 nm channel lengths using hydrodynamic simulations have been investigated. Thermal conductivity of diamond in contrast to thermal conductivity of silicon dioxide is significantly higher. Hence, the heat transfers faster in silicon-on-diamond transistors. Lattice temperature of SODs is lower than that of similar SOIs. By using SODs in Integrated circuits with the first transistor turning on and active, neighboring transistors will have the same level of heat as the active transistor. As a result, the DIBL factor will be increased; this is an undesired phenomenon in CMOS applications. To resolve this issue, we propose a new method which is the thickness reduction of buried diamond layers inside of transistors. Due to this change, DIBL of active transistor will be improved, the exceeding lattice heat of side transistors will be evacuated through the devices and their temperatures will be deduced in large scale.
Mousa M. Mohamed, Mohammed Hueesin Almarshadi
Journal of Electronics Cooling and Thermal Control, Volume 07, pp 45-62; doi:10.4236/jectc.2017.73005

Abstract:
In hot arid countries with severe weather, the summer air conditioning systems consume much electrical power at peak period. Shifting the loads peak to off-peak period with thermal storage is recommended. Model A of residential buildings and Model B of schools and hospitals were used to estimate the daily cooling load profile in Makkah, Saudi Arabia at latitude of 21.42°N and longitude of 39.83°E. Model A was constructed from common materials, but Model B as Model A with 5 - 8 cm thermal insulation and double layers glass windows. The average data of Makkah weather through 2010, 2011 and 2012 were used to calculate the cooling load profile and performance of air conditioning systems. The maximum cooling load was calculated at 15:00 o’clock for a main floor building to a 40-floor of residential building and to 5 floors of schools. A district cooling plant of 180,000 Refrigeration Ton was suggested to serve the Gabal Al Sharashf area in the central zone of Makkah. A thermal storage system to store the excess cooling capacity was used. Air cooled condensers were used in the analysis of chiller refrigeration cycle. The operating cost was mainly a function of electrical energy consumption. Fixed electricity tariff was 0.04 $/kWh for electromechanical counter, and 0.027, 0.04, 0.069 $/kWh for shifting loads peak for the smart digital counter. The results showed that the daily savings in consumed power are 8.27% in spring, 6.86% in summer, 8.81% in autumn, and 14.55% in winter. Also, the daily savings in electricity bills are 12.26% in spring, 16.66% in summer, 12.84% in autumn, and 14.55% in winter. The obtained maximum saving in consumed power is 14.5% and the daily saving in electricity bills is 43% in summer when the loads peak is completely shifted to off-peak period.
Zviad Kovziridze, Natela Nijaradze, Gulnaz Tabatadze, Teimuraz Cheishvili, Maia Mshvildadze, Zviad Mestvirishvili, Vera Kinkladze, Nino Daraxvelidze
Journal of Electronics Cooling and Thermal Control, Volume 07, pp 103-122; doi:10.4236/jectc.2017.74009

Abstract:
Goal: obtaining of composite in the SiC-SiAlON system with the metal thermal method in the nitrogen medium. Method: SiALON-s are solid metal oxide solutions in nitrides. Area of their presence is considered in four-component system-Si3N4-ALN-AL2O3-SiO2. In the present paper SiALON-containing composite was obtained through alum-thermal process in the nitrogen medium on the base of Geopolymer (kaolin and pologycley-Ukraine), SiC, aluminum nano-powder and Si powder with small additives of perlite (Aragatz, Armenia) by the reactive baking method. The advantage of this method is that compounds, which are newly formed thanks to interaction going on at thermal treatment: Si3N4, Si, AlN are active, which contributes to SiALON formation at relatively low temperature, at 1250°C - 1300°C. Results-β-SiAlON was formed at the sintering of SiC-aluminium and silicium powder, geopolymer at 1450°C. Porosity of carbide SiAlON composite obtained by reactive sintering, according to water absorption, equals to 13% - 15%. The samples were fragmented in a jaw-crusher and were powdered in attrition mill till micro-powder dispersion was obtained. Then samples were hot-pressed at 1620°C under 30 MPa pressure. Hold-time at the final temperature was 8 min. Sample water absorption, according to porosity, was less than 0.4%. Further studies were continued on these samples. Conclusion: the paper offers processes of formation of SiC-SiAlON composites and their physical and technical properties. Phase composition of the composites was studied by X-ray diffraction method, while the structure was studied by the use of optic and electron microscope. Electric properties showed that the specimen A obtained by hot-compression is characterized by 2 signs lower resistance than the porous material B, which was used to receive this specimen. Probably this should be connected with transition of the reactively baked structure of the hot-compressed material into compact structure. Obtained materials are used in protecting jackets of thermo couples used for melted metal temperature measuring (18 - 20 measuring) and for constructions used for placing objects in factory furnaces.
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