Electro-Insulating Nanofluids Based on Synthetic Ester and TiO2 or C60 Nanoparticles in Power Transformer

The article discusses thermal properties of synthetic ester admixed with nanoparticles. The analyzed thermal properties were: thermal conductivity λ, kinematic viscosity υ, density ρ, specific heat cp, and the thermal expansion factor β- all obtained by means of measurements. On the basis of these, the authors calculated the heat transfer factor α, which determines the ability of the liquid to heat transport. The authors used nanoparticles of fullerene C60 and titanium oxide TiO2. The analysis of the thermal properties was done for the temperatures of 25, 40, 60 and 80 °C. The authors analyzed the impact of nanoparticles C60 and TiO2 on thermal properties of synthetic ester. They proved that fullerene C60 in principle had no influence on heat transfer factor α of the ester, while titanium oxide TiO2 had some positive influence on the factor, the value of which increased about 1–3%.

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Heat transfer coefficient α of insulation liquid used in power transformers, based on measurements

ITM Web of Conferences ◽

10.1051/itmconf/20181901016 ◽

2018 ◽

Vol 19 ◽

pp. 01016

Author(s):

Przemyslaw Goscinski ◽

Zbigniew Nadolny

Keyword(s):

Heat Transfer ◽

Heat Exchange ◽

Transfer Factor ◽

Heat Load ◽

Surface Heat ◽

Power Transformers ◽

Negative Consequences ◽

Insulation System ◽

Heat Transfer Factor ◽

Factor Α

Proper work of the power transformer is determined by many factors. One of them is relatively low operating temperature of the transformer. Too high temperature has many negative consequences, such as fast aging process of the insulation system. The temperature depends on the load of transmission line, losses and heat exchange in transformer. Heat exchange depends on heat transfer factor α of insulation liquid, which is a component of insulation system of transformer. This factor depends on many factors: the type of insulation liquid, the length of the heating element (windings), temperature, winding surface heat load, the winding position (vertical, horizontal), place on the winding (upper, middle or bottom part). The article presents the results of the measurement of heat transfer factor α as a function of type of insulation liquid, winding surface heat load, and place on the windings. The results will be used by designers and operators of power transformers.

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Determination of the heat-transfer factor characterizing sprayer cooling of continuously cast blanks

Metal Science and Heat Treatment ◽

10.1007/s11041-007-0092-8 ◽

2007 ◽

Vol 49 (9-10) ◽

pp. 497-500 ◽

Cited By ~ 1

Author(s):

A. V. Kushnarev ◽

A. V. Supov ◽

A. E. Khrulev ◽

S. P. Shcherbakov

Keyword(s):

Heat Transfer ◽

Transfer Factor ◽

Heat Transfer Factor ◽

Continuously Cast

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Improvement of Calculation Methods for Heat Transfer Factor in Iron Ore Pellet Bed

KnE Engineering ◽

10.18502/keg.v3i5.2649 ◽

2018 ◽

Vol 3 (5) ◽

pp. 1

Author(s):

E G Dmitrieva ◽

V S Shvydkii ◽

S Ya Zhuravlev ◽

I V Plesakin

Keyword(s):

Heat Transfer ◽

Transfer Factor ◽

Iron Ore ◽

Calculation Methods ◽

Heat Transfer Factor ◽

Iron Ore Pellet

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HEAT TRANSFER ENHANCEMENT USING HELICAL PIPES

International Journal of Advanced Research ◽

10.21474/ijar01/13959 ◽

2021 ◽

Vol 9 (12) ◽

pp. 676-685

Author(s):

Waleed Abdulhadi Ethbayah ◽

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Reynolds Number ◽

Transfer Factor ◽

Enhancement Ratio ◽

Pipe Length ◽

Enhancement Technique ◽

Heat Transfer Factor ◽

Plain Tube ◽

Laminar Forced Convection

The enhancement of laminar forced convection inside helical pipes is studied numerically and compared with plain pipes. The study is achieved numerically using the (Fluent-CFD 6.3.26) software program for solving the governing equations. The heat transfer factor and friction factor are calculated using the enhancement technique and compared with the plain tube. In this research the factors that affect the enhancement technique using helical pipes are studied, these factors are the ratio of (pitch /pipe length) (SL), Reynolds number and the heat flux applied to the external surface of the pipe. The results showed that there is an increasing in the heat transfer factor is related to the decreasing of (SL), increasing of Reynolds number and heat flux. The performance of the helical pipes is evaluated depending on the calculation of (Enhancement ratio), and its found that the enhancement ratio increases as Reynolds number increases and (SL) decreases. It is found that the best enhancement ratio was (200%) at (SR=0.05), (Re=2000),(Heat flux=3000W/m2).The results are compared with the literature and there is a good agreement.

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Experiment and numerical modelling of heat transfer inside calcium aluminate cement-based refractory concrete

Journal of Mining and Earth Sciences ◽

10.46326/jmes.htcs2020.19 ◽

2020 ◽

Vol 61 (HTCS6) ◽

pp. 139-147

Author(s):

Tien Manh Tran ◽

Hong Xuan Vu ◽

Emmanuel Ferrier ◽

Keyword(s):

Heat Transfer ◽

Thermal Properties ◽

Calcium Aluminate ◽

Refractory Concrete ◽

Concrete Specimen ◽

Calcium Aluminate Cement ◽

Experimental Results ◽

Factors Affecting ◽

The Impact ◽

Aluminate Cement

In the case of fire in infrastructure works, the bearing capacity of reinforced-concrete structures will be reduced due to the effect of high temperatures. So, the refractory concrete with good thermal properties contributes an important role in reducing the impact of fire on the durability of the building. Nowadays, calcium aluminate cement is widely used for that thanks to the thermal stability of the respective concrete by the high content of aluminum. This paper presents experimental and numerical results of heat transfer in cylindrical specimens of calcium aluminate cement-based refractory concrete. As experimental results, with a calcium aluminate content of about 50% in concrete, its thermal properties have been significantly improved in comparison with other types of cementitious concrete. The evolution of temperature as a function of time (inside and outside of the concrete specimen) was also recorded and analyzed. In the 3-D model, the thermal properties of refractory concrete were used from the previous experimental results. The results of this model were used to compare with experiments, then analyze and evaluate factors affecting the model results. The numerical model could also be exploited to determine the thermal parameters in the heat transfer in refractory concrete specimen.

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INVESTIGATIONS OF APARTMENT HOUSE CELLAR MICROCLIMATE AND IT’S IMPROVEMENT POSSIBILITIES

Environment Technology Resources Proceedings of the International Scientific and Practical Conference ◽

10.17770/etr2019vol1.4185 ◽

2019 ◽

Vol 1 ◽

pp. 222

Author(s):

Stanislavs Pleiksnis ◽

Edmunds Visockis ◽

Raimunds Selegovskis ◽

Sandra Gusta

Keyword(s):

Heat Transfer ◽

Air Temperature ◽

Transfer Factor ◽

Dew Point ◽

Cold Weather ◽

Apartment House ◽

Heat Transfer Factor ◽

Condensate Formation ◽

Winter Time ◽

Made In

Apartment houses made in the last century in Latvia have rather big heat transfer factor and not good ventilation, especially in cellar. That leads to formation of condensate on building constructions. During cold weather in winter time, this condensate formats ice layer that damages building constructions ant also lead to inconvenience for inhabitants, for example, disturbs opening of cellar door. During investigations the cellar microclimate parameters, such as temperature, humidity and dew point, were measured and different ways to improve them and as result preventing of condensate formation were worked out. The measurements shows that sometimes the air temperature and the temperature on surfaces reaches dew point and therefore the condensate starts to format. The possibilities to eliminate humidity and to increase dew point are worked out during investigations.

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Analysis of Heat Transfer Enhancement in Micro-scale Heat Sink Structure

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4050840 ◽

2021 ◽

pp. 1-11

Author(s):

Long Wei ◽

Zixuan Song ◽

Tao Ren ◽

Yun Liu

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Flow Field ◽

Transfer Factor ◽

Heat Sink ◽

Heat Transfer Performance ◽

Straight Channel ◽

Transfer Enhancement ◽

Enhanced Heat Transfer ◽

Heat Transfer Factor

Abstract With the increasing power requirements of electronic devices, high heat flux will cause serious damage to the devices. Based on the basic theory of micro-nano heat transfer, the series and topological microchannel heat sink models are established. The flow field characteristics and temperature distribution in the heat sink are analyzed by numerical calculation. The effects of channel structure on temperature, pressure drop, the Nusselt number and enhanced heat transfer factor are compared, and the micro-mechanism of heat transfer enhancement in microchannels is clarified. It is found that the Nusselt number of the flow field can be significantly increased by adding the triangular groove in the microchannel, and the enhanced heat transfer factor in the channel can be greatly improved by the topological structure. Further analysis of the factors such as angle a, diameter ratios γ and topological structures of the triangular groove shows that:When α = 70°,the Nusselt number of the flow field is 3.1 times of that of the straight channel, and the enhanced heat transfer factor is 2.7 times of that of it; compared with the straight channel, the comprehensive heat transfer performance of the microchannel with γ = 1/2 is improved by 31%; when using T.Tr.N. topology, the convective heat transfer of the microchannel is 2.6 times of that of the straight channel and the comprehensive heat transfer performance is increased by 5.9 times.

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