Search results for "Heat Transfer"

Multiphysical modeling of dissimilar welding via interlayer

2011

Abstract A multiphysical finite element modeling of dissimilar welding via interlayer material was proposed. A 2D model including heat transfer, fluid flow and level set problems allowed to simulate the morphology and the composition of melted zone in horizontal plane. The calculated thickness of melted interlayer was used as a main criterion for the choice of optimal welding conditions, when the chemical interaction between the joined materials must be avoided. A 1D diffusion model at the limit of melted zone allowed estimating the length and the composition of diffusion layer between one of the materials and the interlayer basing on previously calculated local temperature gradient. The si…

Novel non-destructive evaluation technique for the detection of poor dispersion of carbon nanotubes in nanocomposites

2019

Abstract A wide use of advanced carbon nanotube polymer composites can be boosted by new non-destructive evaluation (NDE) techniques that can test the quality of the products to ensure that their specifications are met. It is well known in literature that the parameter that far more than others can affect the enhancing capabilities of the carbon nanotubes is their dispersion. Here we have presented a novel NDE technique based on infrared thermography able to evaluate the dispersion of the added nanoparticles in polymer nanocomposites. The NDE technique was used to compare pairs of samples whose difference is represented only by the level of dispersion. It was found a significant difference …

Conservative averaging method for solving some nonlinear heat transfer problems related to combustion

2020

Ultrasound-assisted bleaching: Mathematical and 3D computational fluid dynamics simulation of ultrasound parameters on microbubble formation and cavi…

2019

Abstract The implementation of ultrasound-assisted bleaching (UAB) is gaining interest in commercial oil refining, as an alternative to the current bleaching procedure (BP), because this technique has several advantages compared to the conventional BP. The mathematical and 3D computational fluid dynamics (CFD) simulation of the influence of ultrasound power, frequency and temperature for predicting microbubble formation and heat transfer in the ultrasonic treatment of soybean oil was assessed in order to optimize the UAB process. The fluctuation frequency and wave speed showed opposite effects on system response to the imposed pressure pulse. As the bubble radius shrinks to zero (after bubb…

Confinement of charged dust particles by a hybrid-type electric curtain

2012

Abstract The hybrid-type electric curtain (HTEC) comprises a planar electric curtain and a perpendicular planar condenser. Serial cylindrical electrodes are supplied with AC voltage, whereas the condenser is fed with DC voltage. HTEC allows for better control of the particle position shift in space. The particle oscillation path within the hybrid curtain has been photographically analysed. The changing particle path was recorded according to a DC changing voltage value and a constant AC voltage value. The aim of the paper is to describe a successful method that enables one to experimentally determine the region where the particle can be stably oscillated.

Modelling of the thermal mechanical behaviour of a single size beryllium pebble bed

2001

The Helium Cooled Pebble Bed (HCPB) Blanket for fusion power reactors and the ITER breeding blanket are based on the use of pebble beds of lithium ceramics as breeder and beryllium as neutron multiplier. Experimental activities were performed at Forschungszentrum Karlsruhe concerning the measurement of pebble bed heat transfer parameters. At the Department of Nuclear Engineering of the University of Palermo, the experimental results have been reproduced by means of the ABAQUS finite element code. Moreover, a thermal-mechanical theoretical model has been developed for single size beryllium pebble beds. In the paper the results from the numerical and theoretical analyses and the comparison wi…

Dielectric nonlinearity of ferroelectric solid solutions PMN-PZN and PMN-PNN

2001

Abstract Obtaining of novel thin film materials for electrically tuneable capacities is one of the current problems of ferroelectric material application. The most appropriate materials are the ferroelectric lead-containing niobates: PbMg1/3Nb2/3O3 (PMN), PhZn1/3Nb2/3Os (PZN), PbNi1/3Nb2/3O3 (PNN) and their solid solutions were synthesized by solid state reactions at 800–900 °C from oxides. Results of the studies of thermal dependence of dielectric permeability and loss factors of the synthesized solutions are provided together with reciprocal dielectric permeability as function of temperature and electric field intensity. The dielectric characteristics of nonlinear materials are reported e…

The boron effect on low temperature luminescence of SrAl2O4:Eu, Dy

2020

V.V. acknowledges the financial support of ERDF PostDoc project No. 1.1.1.2/VIAA/3/19/440 (University of Latvia Institute of Solid State Physics, Latvia) and K.S., I.B., A.Z., D.M. and K.L. acknowledge the financial support of ERDF, European-Union Project No. 1.1.1.1/16/A/182 (University of Latvia Institute of Solid State Physics, Latvia).

Numerical investigation of laser beam shaping for heat transfer control in laser processing

2002

This article presents a thermal finite volume model adapted to investigate laser processes. It is specially developed to treat moving heat sources with phase changes, melting and vapourisation. Heat transfer control in laser processing is particularly useful when processes must respect prescribed temperatures, or more generally, prescribed constraints. These processes involve generally several laser sources, or non-conventional power distribution. Hence, they have numerous parameters to set. Experimental optimisation is difficult and may be expansive. The numerical model is a useful and cheaper tool for development of those complex processes. For example in this article, two special laser p…

Temperature Sensor Based on Colloidal Quantum Dots PMMA Nanocomposite Waveguides

2012

In this paper, integrated temperature sensors based on active nanocomposite planar waveguides are presented. The nanocomposites consist of cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) embedded in a polymethylmethacrylate (PMMA) matrix. When the samples are heated in a temperature range from 25$^{circ}{rm C}$ to 50 $^{circ}{rm C}$, the waveguided photoluminescence of QDs suffers from a strong intensity decrease, which is approximately quadratic dependent on temperature. Moreover, the wavelength peak of the waveguided emission spectrum of CdTe-PMMA shows a blue shift of 0.25 ${rm nm}/^{circ}{rm C}$, whereas it remains constant in the case of CdSe-PMMA. A temperature…