3D Thermal Field Research Articles

Specific properties of ferritic/austenitic Dissimilar Metals Welded Joints

This paper addresses several peculiar properties of ferritic/austenitic welded joints (Black and White Joints-BWJ) of thin sheets, which are emerging nowadays due to cost saving and satisfactory service performance. Starting from 3D thermal field modelling approached by considering Goldak’s double ellipsoidal heat source, together with a contribution of the authors, a 2D FEM-based model was used for arc welding of low carbon steel (CS) and stainless steel (SS) of thin sheets (3 mm). Conclusion helped to conduct experiments of BWJ arc welding (MMA and TIG), and laser-GMA hybrid welding, whilst infrared thermographic measurements were compared with the FEM results. Besides microstructural examination and mechanical characterization (hardness and tensile), fracture toughness and stress corrosion tests were performed on the BWJ laser hybrid welded. Whilst the model has offered important qualitative information about the asymmetric thermal field and the heat apportionment on the molten metal pool formation, the experiments have shown inadequate microstructures and constitutions of the welds for MMA and TIG welding, with respect to laser-GMAW hybrid joints. The description of the experimental program focused on B&W laser-GMA hybrid welding of thin plates aiming a characterization procedure using fracture mechanics methods is briefly presented.

Research on the 3D Temperature Field of Transformer Winding Based on Finite Element Analysis

Power transformer is one of the most important electric equipments in power network, its running state has a direct effect on its safe operation of power network. Fault’s occurrence of power transformer probably result in vast hazards or accidents. According to statistics, its over-temperature operation of winding often result in different fault patterns, such as aging, breakdown and its burnt, etc, which has a large proportion in its accidents of power transformer. In this paper, based on the thermal analysis theory, a 3D thermal field model of transformer’s winding and core is respectively established in ANSYS software environment. And its 3D temperature field distribution of power transformer, including winding and core is simulated. Numerical simulated results provide a reliable and convenient reference for its thermal performance analysis of power transformer.is simulated. Numerical simulated results provide a reliable and convenient reference for its thermal performance analysis of power transformer.

Computer modelling of 3D transient thermal field coupled with electromagnetic field in three‐phase induction motor on load

PurposeThe purpose of this paper is to present the plan to develop the known algorithm for thermal and electromagnetic coupled problem calculation. This is used for three‐phase induction motor (IM) on nominal load. An additional purpose is verification empiric expressions of the heat transfer and equivalent thermal conductivity coefficients for external faces and air zones in analysed motor taken from literature.Design/methodology/approachThe numerical investigations proposed in this paper are based on 3D finite element models for thermal and electromagnetic fields analysis. Electromagnetic analysis includes iron core losses. It gives additional heat sources to thermal analysis. Heat transfer and equivalent thermal conductivity coefficients are assessed applying empiric expressions. Thermal model is experimentally validated.FindingsThe results of calculations and experimental test shows that heat transfer coefficient for external zones taken from literature does not guarantee the equal accuracy of the distribution of the temperature in all volume of the machine.Research limitations/implicationsTaken from literature, empirical equations do not give correct values of heat transfer coefficient. It states ways to go further in the evaluation of heat transfer coefficients.Originality/valueThis paper presents modelling methodology of 3D transient thermal field coupled with electromagnetic field applied in three‐phase IM at rated load conditions.

Transient natural convection in 3D tilted enclosure heated from two opposite sides

In the present work, we investigate numerically the natural convection flow in 3D cubic enclosure tilted at an angle ( γ) with respect to the vertical position. The enclosure is heated and cooled from the two opposite walls while the remaining walls are adiabatic. The numerical procedure adopted in this analysis yield consistent performance over a wide range of parameters. Simulations have been carried out for Rayleigh numbers Ra ranging from 10 3 to 1.3 × 10 5, Prandtl number, Pr, (0.71 ≤ Pr ≤ 75) and inclination angle γ (0° ≤ γ ≤ 90°). Particular attention is focused on the three-dimensional steady effects that can arise in such configuration that seem to be unknown in the literature, even for relatively small values of the Rayleigh number. The 3D flow characteristics and thermal fields are analyzed in terms of streamlines, isotherms and Nusselt numbers. A periodic behavior of the 3D flow has been observed at Ra = 8.5 × 10 4 with a fundamental frequency of 8.27. The Hopf bifurcation is localized. In addition, time-dependent solutions reveal that the flow characteristics depend on the inclination angle γ. The effects of Prandtl number on heat transfer and fluid flow is significant for Pr ≥ 6.

Computer modelling of 3D transient thermal field coupled with electromagnetic field in one‐phase induction motor with locked rotor

Purpose – This paper aims to present the plan to develop the known algorithm for thermal and electromagnetic coupled problem calculation. This is used for a one‐phase induction motor with locked rotor for nominal and lowered voltage excitation values. It also aims to prepare a calculating method for the average heat transfer coefficient for natural convection from the induction motor housing external face.Design/methodology/approach – The numerical investigations proposed are based on 3D finite element models for thermal and electromagnetic fields analysis and 3D volume element model for average heat transfer coefficient calculations. The thermal model is experimentally validated.Findings – The paper provides a numerical method to calculate average heat transfer coefficient for the induction motor housing external faces. This coefficient is shown as a temperature function. Temperature variations in the various parts of the induction motor with locked rotor are calculated. The calculation results are compa...

Tomographic particle-image velocimetry and thermography in Rayleigh-Bénard convection using suspended thermochromic liquid crystals and digital image processing

Steady-state flow and temperature fields in shallow rectangular enclosures heated from below were visualized and quantitatively characterized by using glycerol as the working fluid and suspended thermochromic liquid crystals as tracers. Couples of photographs taken on 120 transparency film for two orthogonal sets of vertical plane sections were digitized by a 1,200-dpi flatbed scanner and split into HSL (hue-saturation-lightness) components by using commercial general-purpose image processing software. Two-dimensional velocity fields were obtained from the lightness component by a two-frame cross-correlation technique using a commercial particle-image velocimetry (PIV) package. Temperature fields were obtained from the hue component on the basis of an in situ calibration procedure, conducted under conditions of stable thermal stratification. Finally, 2D flow and temperature distributions were interpolated by a purpose-written Fortran program to give 3D flow and thermal fields in the enclosure. Results are presented here for the case of a 1:2:4 aspect ratio cavity at a Rayleigh number of ∼ 14,500, for which a complex 3D flow and temperature distribution was observed.

Modeling of the 3D thermal field in the northeast German basin

The regional thermal field of the NE-German basin is modeled by a three-dimensional finite-element approach and is compared to classical one-dimensional extrapolations. Two alternative boundary conditions are assumed at the approximate depth of the Moho: a constant temperature distribution and a constant heat flow. Surprisingly, both results are almost identical down to approximately 10 km depth. Based on the models presented, the results are due to a complex interaction of different strata and the related regional variability of conductivities. In addition, the available temperature maps for different depths (Hurtig et al. 1992) indicate a relative high heat flow at the basin margins especially at the southern and eastern boundary. The models are able to reproduce the generalized pattern by regarding only a conductive heat flow. However, because both models are successful at shallow depth, we conclude that the current techniques of thermal modeling require improvement, even on the theoretical aspects of depth continuation and inversion.

Holographic tomography by SART and it's application to reconstruction of 3D temperature distribution

Application of holographic tomography to reconstruction of 3D asymmetric temperature distribution is experimentally and numerically investigated. A new simultaneous algebraic reconstruction technique (SART) code for holographic tomography is presented. Important features of SART for reconstruction of temperature field were evaluated using numerical model functions. Data from diffuse-illumination holographic interferograms obtained at twenty different view directions and with 40° range of view angles were used to reconstruct a 3D thermal flow field by SART method. An average reconstruction error of about 5% is estimated. The ability to reconstruct the 3D field using a limited viewing range implies that SART is especially suitable for the holographic tomography of aerodynamic density field.