1,721,043 research outputs found
Transient analysis of heat transfer in parallel squared channels for high temperature thermal storage
No full textAn investigation on honeycomb solid matrix systems employed for high temperature thermal storage is provided numerically considering two models in the transient regime. The two models are related to a direct model with multiple channels and a porous medium model. The system with parallel squared section channels is described by a conjugated convective-conductive model by coupling the governing equations for fluid and solid matrix. The porous medium is modeled by assuming a Brinkman-Forchheimer-extended Darcy model and the LTNE is assumed. The models for different number of parallel squared channels or pores per unit of length (PPU) are considered. The honeycomb system is considered as an anisotropic porous medium, and assuming that the thermal storage system is adiabatic in order to estimate fluid dynamic and thermal characteristics for different PPU values. The Ansys-Fluent code is used to solve numerically the governing equations for both models. Results in terms of solid and fluid temperature profiles are given for different PPU values and for both models; they show that the two models are in very good agreement. The main consequence is that a honeycomb system can be simulated as a porous medium allowing a simpler numerical simulation also for parallel channel systems with high PPU. It is found that for high PPU systems the charging time decreases and for assigned partial charging time an increase in stored thermal energy is detected increasing the PPU value. © 2015 by Begell House, Inc
Effects of high Reynolds number impinging jet on the heat conduction in work-pieces irradiated by a moving heat source
No full textA three dimensional conductive field is analyzed and solved numerically by means of a commercial code. The investigated work-pieces are made up of a simple brick-type solid. A laser source with combined donut-Gaussian distributions is considered moving with a constant velocity along motion direction. The solid dimension along the motion direction is assumed to be infinite or semi-infinite, while finite width (2ly) and thickness (s) are considered. Thermal properties are considered temperature dependent and the materials are considered isotropic. Surface heat losses toward the ambient are taken into account. Several Reynolds numbers of the impinging jet, Biot and Peclet numbers are considered with negligible radiative heat losses. Results are presented in terms of temperatures field and profile to evaluate the effect of impinging jet. © (2014) Trans Tech Publications, Switzerland
A numerical analysis on nanofluid mixed convection in triangular cross-sectioned ducts heated by a uniform heat flux
No full textIn this paper, results obtained by the numerical investigation on laminar mixed convection in triangular ducts, filled with nanofluids, are presented in order to evaluate the fluid dynamic and thermal features of the considered geometry by considering Al2O3/water based nanofluids. The system is heated by a constant and uniform heat flux also along the perimeter of the triangular duct section in H2 mode as thermal boundary condition and the single-phase model has been assigned for a Reynolds number value equal to 100. Results are given for different nanoparticle volume concentrations and Richardson number values ranging from 0% to 5% and from 0 to 5, respectively. Results, presented for the fully developed regime flow, show the enhancement of average convective heat transfer coefficients values for increasing values of Richardson number and particle fractions. However, wall shear stress and required pumping power profiles increase as expected. The PEC analysis showed that the use of nanofluids in mixed convection seems slightly convenient. It should be underlined that, at the moment, experimental data are not available to compare the numerical proposed model for mixed convection in horizontal triangular ducts with nanofluids. Copyright © Oronzio Manca et al
Numerical analysis on nanofluid mixed convection in triangular ducts heated by a constant heat flux
No full text
A numerical analysis on nanofluid mixed convection in triangular cross-sectioned ducts heated by a uniform heat flux
No full textIn this paper, results obtained by the numerical investigation on laminar mixed convection in triangular ducts, filled with nanofluids, are presented in order to evaluate the fluid dynamic and thermal features of the considered geometry by considering Al2O3/water based nanofluids. The system is heated by a constant and uniform heat flux also along the perimeter of the triangular duct section in H2 mode as thermal boundary condition and the single-phase model has been assigned for a Reynolds number value equal to 100. Results are given for different nanoparticle volume concentrations and Richardson number values ranging from 0% to 5% and from 0 to 5, respectively. Results, presented for the fully developed regime flow, show the enhancement of average convective heat transfer coefficients values for increasing values of Richardson number and particle fractions. However, wall shear stress and required pumping power profiles increase as expected. The PEC analysis showed that the use of nanofluids in mixed convection seems slightly convenient. It should be underlined that, at the moment, experimental data are not available to compare the numerical proposed model for mixed convection in horizontal triangular ducts with nanofluids
Numerical simulation of transient temperature fields in solids irradiated by moving gaussian and donut sources
No full text
Numerical investigation on thermal and fluid dynamic interaction between a car underbody and its exhaust system
No full text- …
