Investigation of the Thermal Transfer Coefficient by the Energy Balance of Fault Arcs in Electrical Installations

2006 ◽  
Vol 21 (1) ◽  
pp. 425-431 ◽  
Author(s):  
X. Zhang ◽  
G. Pietsch ◽  
E. Gockenbach
Keyword(s):  
Energy Balance ◽  
Transfer Coefficient ◽  
Thermal Transfer

Fundamental investigation on the thermal transfer coefficient due to arc faults

2006 ◽  
Vol 34 (3) ◽  
pp. 1038-1045 ◽  
Author(s):  
Xiang Zhang ◽  
G. Pietsch ◽  
Jiaosuo Zhang ◽  
E. Gockenbach
Keyword(s):  
Transfer Coefficient ◽  
Thermal Transfer ◽  
Fundamental Investigation

Experimental Studying Nanofluid Thermal Transfer In Microchannel

2016 ◽  
Vol 11 (2) ◽  
pp. 5-11
Author(s):  
Vladimir Aniskin ◽  
Valeriy Rudyak
Keyword(s):  
Silicon Dioxide ◽  
Transfer Coefficient ◽  
Volume Fraction ◽  
Micro Channel ◽  
Thermal Transfer ◽  
Nanoparticles Volume Fraction ◽  
Inner Diameter ◽  
Average Size ◽  
Silicon Dioxide Nanoparticle ◽  
Base Liquid

In paper new setup for studying the thermal transfer of nanofluid in the steel micro-channel with inner diameter 358 microns is described. Setup testing carried out by means of known experimental data about thermal transport of the water. Then the data about the thermal tranfer coefficient of the water based nanofluids with silicon dioxide nanoparticle with average size 25 nm are discussed. It was shown that nanofluids have the thermal transfer coefficient much more than that of base liquid. The enhancement of the thermal transfer coefficient of one-percent nanofluid is about 60 %. This enhancement grows with increasing of the nanoparticles volume fraction and flow rate of the nanofluid.

Application of Double-Sided Heat Flow Meter in Testing of Overall Heat Transfer Coefficient of Building Envelope

2013 ◽  
Vol 353-356 ◽  
pp. 2872-2876
Author(s):  
Hai Rong Dong ◽  
Shao Ming Qi
Keyword(s):  
Heat Flow ◽  
Thermal Property ◽  
Transfer Coefficient ◽  
Energy Saving ◽  
Field Testing ◽  
Building Envelope ◽  
Existing Buildings ◽  
Flow Meter ◽  
Thermal Transfer ◽  
Heat Flow Meter

It is essential to find out the thermal property of building envelope in order to design economical and reasonable scheme of energy-saving reconstruction. Field testing is a method of receiving the thermal property of envelope when existing buildings are reconstructed. In this paper, we focus on the need for obtaining the thermal transfer coefficient. A methoddouble-sided heat flow meter was introduced and used to test the thermal property of wall. The testing results show that it provides a feasible method for colleting basal data of energy-saving reconstruction of existing buildings.

Application of the Time-Dependent Overall Heat-Transfer Coefficient Concept to Heat-Transfer Problems in Porous Media

1984 ◽  
Vol 24 (01) ◽  
pp. 107-112 ◽  
Author(s):  
Abdurrahman Satman ◽  
Anatoly B. Zolotukhin ◽  
Mohamed Y. Soliman
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Transfer Coefficient ◽  
Energy Balance ◽  
Transfer Coefficient ◽  
Heat Loss ◽  
Thermal Recovery ◽  
Time Dependent ◽  
Overall Heat Transfer Coefficient ◽  
Recovery Processes

Abstract Prediction of temperature distribution behavior during thermal recovery processes is necessary for engineering, evaluation of field operations. Such a prediction can be used in the case of hot- and cold-water injection into a reservoir and also applies in some other thermal recovery processes, such as in-situ combustion and steam-flooding. The mathematical formulas discussed involve the concept of a time-dependent overall heat-transfer coefficient. In the first portion of the paper, we discuss two new analytical solutions that describe the temperature distribution in linear and radial reservoirs in the case of hot- and cold-water injection. A comparison with published laboratory hot-water injection data demonstrates the validity of the solution for linear geometry. Since the new analytical model considers the heat conduction in addition to convection and heat loss. It describes the thermal behavior in a more general form than does Lauwerier's model. These two models are compared also. The application of the time-dependent overall heat-transfer coefficient concept to the thermal behavior of the steam plateau portion of the in-situ combustion process is discussed in the second pail of the paper. The result is fairly satisfactory. Introduction Since the mid-1950's, many models describing the temperature behavior and thermal efficiency of fluid injection into porous media have been formulated and solved analytically. In particular, increasing demands for thermal oil recovery processes and heat extraction processes from geothermal fields have led researchers to develop these models. With advancements in numerical solution techniques, it also has become possible to obtain solutions to problems that could not have been solved before. Heat-transfer models in porous media consider three heat-transfer mechanisms: thermal conduction, convective transfer between fluid and solid matrix, and energy transfer resulting from fluid flow. The conductive heat transfer describes the thermal conduction in the direction of flow. Convective heat transfer is accounted for by the assumption of thermal equilibrium between the porous medium and its contained fluids. The heat loss caused by fluid injection plays an important role. Keeping the loss low is a primary concern for the efficiency of thermal recovery processes. Although the heat is transferred by a combination of both conduction and convection, in earlier formulations of the energy balance of flow in porous media, the heat loss generally has been treated as either a convective or conductive heat-transfer mechanism. A constant overall heat-transfer coefficient, U, can be used to describe the heat transfer from the system to the adjacent strata: q = UA (T-Ti)........................................(1) This has proved a reasonable approximation for the heat-loss mechanisms occurring in nonadiabatic laboratory tube experiments. Eq. 1 describes the heat loss in a convective form. Heat loss in conductive form can be written as Tq=k A ---- ........................................(2)adj y However, such formulation of heat loss leads to a two-dimensional energy balance equation for one-dimensional flow geometry or a three-dimensional energy balance equation for two-dimensional flow geometry. The solutions of such energy-balance equations become difficult. Lauwerier used the conductive form of heat loss in his model and developed an analytical solution for temperature propagation in a linear flow geometry. He assumed all infinite thermal conductivity in the vertical direction within permeable sand. The reservoir and surrounding formation thermal conductivities in the horizontal direction, however, were neglected. Later, in 1959, Rubinshtein developed it more sophisticated analytical model for heat flow in porous media. His model removed the restrictions in dealing with the thermal conductivities in Lauwerier's model. SPEJ P. 107^

Thermal Modeling for High Thermal Conductivity Thermal Ground Planes

2012 ◽  
Author(s):  
Mohammed T. Ababneh ◽  
Pramod Chamarthy ◽  
Shakti Chauhan ◽  
Frank M. Gerner ◽  
Peter de Bock ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Energy Balance ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Interfacial Energy ◽  
Interfacial Heat Transfer Coefficient ◽  
Interfacial Heat Transfer ◽  
Vapor Liquid

Thermal ground planes (TGPs) are flat, thin (external thickness of 2 mm) heat pipes which utilize two-phase cooling. The goal is to utilize TGPs as thermal spreaders in a variety of microelectronic cooling applications. TGPs are novel high-performance, integrated systems able to operate at a high power density with a reduced weight and temperature gradient. In addition to being able to dissipate large amounts of heat, they have very high effective axial thermal conductivities and (because of nano-porous wicks) can operate in high adverse gravitational fields. A three-dimensional (3D) finite element model is used to predict the thermal performance of the TGP. The 3D thermal model predicts the temperature field in the TGP, the effective axial thermal conductivity, and the evaporation and the condensation rates. A key feature of this model is that it relies on empirical interfacial heat transfer coefficient data to very accurately model the interfacial energy balance at the vapor-liquid saturated wick interface. Wick samples for a TGP are tested in an experimental setup to measure the interfacial heat transfer coefficient. Then the experimental heat transfer coefficient data are used for the interfacial energy balance. Another key feature of this model is that it demonstrates that for the Jakob numbers of interest, the thermal and flow fields can be decoupled except at the vapor-liquid saturated wick interface. This model can be used to predict the performance of a TGP for different geometries and implementation structures. This paper will describe the model and how it incorporates empirical interfacial heat transfer coefficient data. It will then show theoretical predictions for the thermal performance of TGP’s, and compare with experimental results.

Structures of Aluminum Base Alloys Solidified by Vibrations

2015 ◽  
Vol 1128 ◽  
pp. 88-97 ◽  
Author(s):  
Mirela Popescu ◽  
Béla Varga
Keyword(s):  
Transfer Coefficient ◽  
Structural Changes ◽  
Mechanical Vibrations ◽  
Qualitative And Quantitative ◽  
Thermal Transfer ◽  
Casting Alloys ◽  
Cooling Intensity ◽  
Structure Improvement ◽  
Quantitative Examination ◽  
Aluminum Base

As it is known the improving of the casting alloys properties supposes both finishing and modifying their structure. Dates from castings production specify that for structure improvement the metallurgical methods are more preferred than physical ones. The study analyzes the structural changes caused by melt vibration during crystallization of hypoeutectic and eutectic silumins and of the aluminum-copper alloy. The analysis of solidification conditions was achieved by recording cooling curves, and by the qualitative and quantitative examination of the obtained structures. The monitoring of the cooling intensity with or without mechanical vibrations was performed by calculate the global thermal transfer coefficient. It was followed in the same time the influence of mechanical vibrations on the casting alloys compactity. Global thermal transfer coefficient value increased 3.5 times.

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