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heat-convection
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A three dimensional simulation of spray cooling and its evaporating liquid film generated on patterned surfaces
, Article International Journal of Multiphase Flow ; Volume 155 , 2022 ; 03019322 (ISSN) ; Jowkar, S ; Morad, M. R ; Shen, X ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Liquid impingement cooling in the form of jet or spray is an appropriate method to remove heat from small surfaces progressively utilized in industry. In this study, numerical simulations are conducted to investigate the effect of surface structure on heat transfer characteristics. Five different three-dimensional structured surfaces are investigated using Euler-Lagrangian approach. The effect of surface structures is discussed on the liquid film thickness, the liquid film velocity, and the heat flux with its uniformity for a given spray and temperature characteristics. The results show that the convective heat transfer strongly depends on both liquid film thickness and velocity. While the...
Experimental investigation of forced convective heat transfer coefficient in nanofluids of Al2O3/EG and CuO/EG in a double pipe and plate heat exchangers under turbulent flow
, Article Experimental Thermal and Fluid Science ; Volume 35, Issue 3 , April , 2011 , Pages 495-502 ; 08941777 (ISSN) ; Oskouie, S. N ; Doosthoseini, A ; Joneidi, A ; Pazouki, M ; Sharif University of Technology
2011
Abstract
Nanofluid is the term applied to a suspension of solid, nanometer-sized particles in conventional fluids; the most prominent features of such fluids include enhanced heat characteristics, such as convective heat transfer coefficient, in comparison to the base fluid without considerable alterations in physical and chemical properties. In this study, nanofluids of aluminum oxide and copper oxide were prepared in ethylene glycol separately. The effect of forced convective heat transfer coefficient in turbulent flow was calculated using a double pipe and plate heat exchangers. Furthermore, we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical...
Experimental investigation into laminar forced convective heat transfer of ferrofluids under constant and oscillating magnetic field with different magnetic field arrangements and oscillation modes
, Article Experimental Thermal and Fluid Science ; Volume 68 , November , 2015 , Pages 601-611 ; 08941777 (ISSN) ; Moazami Goudarzi, H ; Shafii, M. B ; Sharif University of Technology
Elsevier Inc
2015
Abstract
In this study, the effects of ferrofluids on the forced convective heat transfer in a tube with a round cross section under constant heat flux in the laminar flow regime are investigated experimentally. For this purpose, an experimental setup was designed and built. Furthermore, the effects of an external magnetic field on the forced convective heat transfer were examined for various Reynolds numbers and volume concentrations. The parameters of magnetic field strength, magnetic field arrangement, the constancy or oscillation of the magnetic field and also its oscillatory mode were examined. As a result of the experimental studies, in the absence of a magnetic field enhancement in convective...
Thermal, thermodynamic and exergoeconomic investigation of a parabolic trough collector utilizing nanofluids
, Article Applied Thermal Engineering ; Volume 206 , 2022 ; 13594311 (ISSN) ; Golab, E ; Nasiri Sadr, A ; Vafai, K ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The exploitation of solar energy facilitates the renewable energy paradigm. In this regard, parabolic trough collectors (PTC) are considered as a useful set-up to absorb solar energy. Simultaneous study of thermal, thermodynamic, and exergoeconomic performance of PTC systems paves the way for designers and manufacturers to not only have a better insight into understanding the underlying concepts about the operation of PTC systems but also to find the most effective and cost-effective circumstances. This study aims at analyzing a practical PTC system by considering an evacuated absorber tube with glass cover, non-uniform heat flux, and taking into account the convective and radiative heat...
A thermoelasticity solution of sandwich structures with functionally graded coating
, Article Composites Science and Technology ; Volume 67, Issue 6 , 2007 , Pages 1073-1080 ; 02663538 (ISSN) ; Haftbaradaran, H ; Asghari, M ; Sharif University of Technology
2007
Abstract
An exact thermoelasticity solution for a two-dimensional thick composite consisting of homogeneous and functionally graded layers is presented. The thermomechanical properties of functionally graded layers are assumed to vary exponentially through the thickness while the Poisson's ratio is taken to be constant. The heat transfer problem is solved under steady state condition accounting for the heat convection. Utilizing the stress function the governing equation reduces to a fourth order inhomogeneous partial differential equation which is solved exactly using Fourier series method. A comparative study is done between two sandwich structures with homogeneous and functionally graded coatings,...
Experimental investigation on laminar forced convective heat transfer of ferrofluid loaded with carbon nanotubes under constant and alternating magnetic fields
, Article Experimental Thermal and Fluid Science ; Volume 76 , 2016 , Pages 1-11 ; 08941777 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Elsevier Inc
Abstract
In this paper, the effects of both constant and alternating magnetic fields on the laminar forced convective heat transfer of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) flowing through a heated tube were investigated experimentally. The experiments were carried out over wide range of parameters such as Reynolds number (548-2190), volume concentrations of Fe3O4 (0.5-0.9%) and carbon nanotube (0.25-1.35%) nanoparticles, magnetic field strength (300-700 Gauss) and alternating magnetic field frequency (10-50 Hz). In present study, the experimental observations in the case without magnetic field...
Series solution for heat transfer of continuous stretching sheet immersed in a micropolar fluid in the existence of radiation
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 23, Issue 2 , 2013 , Pages 289-304 ; 09615539 (ISSN) ; Kimiaeifar, A ; Bagheri, D ; Sharif University of Technology
2013
Abstract
Purpose - The purpose of this paper is to study a two-dimensional steady convective flow of a micropolar fluid over a stretching sheet in the presence of radiation with constant temperature. Design/methodology/approach - The corresponding momentum, microrotation and energy equations are analytically solved using homotopy analysis method (HAM). Findings - To validate the method, investigate the accuracy and convergence of the results, a comparison with existing numerical and experimental results is done for several cases. Finally, by using the obtained analytical solution, for the skin-friction coefficient and the local Nusselt number as well as the temperature, velocity and angular velocity,...
A parametric study on radiant floor heating system performance
, Article Renewable Energy ; Volume 31, Issue 10 , 2006 , Pages 1617-1626 ; 09601481 (ISSN) ; Farhanieh, B ; Sharif University of Technology
2006
Abstract
Efficient radiant heating systems are promising technologies for energy saving in commercial and building sectors together with improving occupant thermal comfort. However, the thermal performance of radiant systems in buildings has not been fully understood and accounted for in currently available building energy simulation software. In this paper, the effects of design parameters on performance of a typical radiant floor heating system have been studied using finite element method. A radiant heating system includes a number of pipes filled with hot water. Therefore, several design parameters such as pipe diameter, type (material), number, thickness and cover of system are affected on the...
Two-dimensional free convection heat transfer below a horizontal hot isothermal flat strip
, Article Journal of Heat Transfer ; Volume 137, Issue 5 , May , 2015 ; 00221481 (ISSN) ; Nouri Gheimassi, A ; Salari, A ; Behshad Shafii, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2015
Abstract
Convection heat transfer below a horizontal, hot, and isothermal strip of infinite length and width of 2L embedded in fluids with different Prandtl number (Pr) and Nusselt number (Nu) is analyzed with the aid of integral method. A new concept is utilized to determine the boundary layer thickness at the strip's edge, which is based on matching the flow rate of the boundary layer below the strip at its edge and the flow rate of the plume, which forms after the heated fluid detaches from the strip's edge. In addition to these novelties, a numerical model is developed to verify the analytical framework, and an excellent agreement is observed between the analytical and numerical models
An experimental study on the proper criterion to judge the thermal performance of the nanofluids
, Article International Communications in Heat and Mass Transfer ; Volume 82 , 2017 , Pages 20-28 ; 07351933 (ISSN) ; Jafari, M ; Nasirivatan, S ; Osanloo, B ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
This work is dedicated to finding a suitable measure to judge thermal performance of nanofluids. The importance of this issue arises from misleading claim of excess heat transfer of nanofluids compared to the base fluid, neglecting the hydraulic effects such as increase in pressure drop. To clarify the issue, the experimental setup with capability to create constant Reynolds number and constant pumping power is constructed. Thermal behavior of nanofluids of silicon oxide/water and aluminum oxide/water and distilled water in developing region of laminar flow regime is investigated. In this regard, the convective heat transfer coefficient within the finned tube heat exchanger is evaluated....
Numerical simulation of turbulent heat transfer on a rotating disk with an impinging jet
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 2 , 2010 , Pages 627-631 ; 9780791849163 (ISBN) ; Karrabi, H ; Avval, H. B ; Asgarshamsi, A ; Sharif University of Technology
Abstract
A numerical study has been carried out to investigate the fluid flow structure and convective heat transfer due to a circular jet impinging on a rotating disk. The temperature distribution and convection heat transfer coefficient on the disk are calculated. Flow is considered to be steady, incompressible and turbulent. k-e RNG model is used to model the turbulent flow. Two new criteria are introduced and used to evaluate the performance of cooling process which are maximum temperature difference on the disk and the average temperature of the disk. The first parameter shows the uniformity of temperature distribution in the disk and the second shows the effect of both thermo physical...
Computational simulation of marangoni convection under microgravity condition
, Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 513-524 ; 10263098 (ISSN) ; Taeibi Rahni, M ; Asadi, B ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
In this work, the rising of a single bubble in a quiescent liquid under microgravity condition was simulated. In addition to general studies of microgravity effects, the initiation of hydrodynamic convection, solely due to the variations of interface curvature (surface tension force) and thus the generation of shearing forces at the interfaces, was also studied. Then, the variation of surface tension due to the temperature gradient (Marangoni convection), which can initiate the onset of convection even in the absence of buoyancy, was studied. The related unsteady incompressible full Navier-Stokes equations were solved using a finite difference method with a structured staggered grid. The...
Multiscale modeling of coupled thermo-hydro-mechanical analysis of heterogeneous porous media
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 391 , 2022 ; 00457825 (ISSN) ; Khoei, A. R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
This paper presents a numerical multiscale formulation for analysis of the transient heat and fluid flow in deformable heterogeneous porous media. Due to the heterogeneity of the media, the direct numerical simulation of the micro-structures leads to high computational costs. Hence, the multi-scale method can provide an efficient computational procedure. To this end, the first-order computational homogenization is adopted for two-scale simulation of THM problems. The governing equations of the problem contain a stress equilibrium equation, a mass continuity equation and an advection–diffusion equation in a fully coupled manner. Accordingly, the proper virtual power relations are defined as a...
CFD modeling of turbulent convection heat transfer of nanofluids containing green functionalized graphene nanoplatelets flowing in a horizontal tube: Comparison with experimental data
, Article Journal of Molecular Liquids ; Volume 269 , 2018 , Pages 152-159 ; 01677322 (ISSN) ; Mallah, A. R ; Hosseini, M ; Ahmadi, G ; Kazi, S. N ; Dabbagh, A ; Yeong, C. H ; Ahmad, R ; Yaakup, N. A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In this research, a series of numerical simulations were conducted utilizing computational fluid dynamics (CFD) software in order to predict the heat transfer performance of queues nanofluids containing clove-treated graphene nanoplatelets (CGNPs) flowing in a horizontal stainless steel heated pipe. The GNPs were covalently functionalized with clove buds using free radical grafting reaction using an eco-friendly process. The advantage of this synthesis method was that it did not use hazardous acids, which are typically used in traditional treatment methods of carbon nanostructures. The thermo-physical properties of the aqueous nanofluids obtained experimentally were used as inputs for the...
Experimental study on heat transfer augmentation of graphene based ferrofluids in presence of magnetic field
, Article Applied Thermal Engineering ; Volume 114 , 2017 , Pages 415-427 ; 13594311 (ISSN) ; Mehrali, M ; Akhiani, A. R ; Tahan Latibari, S ; Dolatshahi Pirouz, A ; Metselaar, H. S. C ; Mehrali, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
The effect of a permanent magnetic field on the heat transfer characteristics of hybrid graphene-magnetite nanofluids (hybrid nanofluid) under forced laminar flow was experimentally investigated. For this purpose, a reduced graphene oxide-Fe3O4 was synthesized by using two-dimensional (2D) graphene oxide, iron salts and tannic acid as the reductant and stabilizer. Graphene sheets acted as the supporting materials to enhance the stability and thermal properties of magnetite nanoparticles. The thermo-physical and magnetic properties of this hybrid nanofluid have been widely characterized and it shows that the thermal conductivity increased up to 11%. The hybrid nanofluid behaves as a Newtonian...
Joule heating effects in electrokinetically driven flow through rectangular microchannels: An analytical approach
, Article Nanoscale and Microscale Thermophysical Engineering ; Volume 17, Issue 3 , 2013 , Pages 173-193 ; 15567265 (ISSN) ; Kazemi, Y ; Saidi, M. H ; Sharif University of Technology
2013
Abstract
This is a theoretical study dealing with mixed electroosmotic and pressure-driven flow of a Newtonian liquid in a rectangular microchannel. Both and thermal boundary conditions are considered and the Debye-Hückel linearization is invoked. The governing equations are made dimensionless assuming fully developed conditions and then analytically solved using an infinite series solution. The governing factors are found to be the dimensionless Debye-Hückel parameter, velocity scale ratio, dimensionless Joule heating parameter, and channel aspect ratio. The results indicate that the Nusselt number is an increasing function of the channel aspect ratio, whereas the opposite is true for the velocity...
Gaseous slip flow forced convection through ordered microcylinders
, Article Microfluidics and Nanofluidics ; Volume 15, Issue 1 , 2013 , Pages 73-85 ; 16134982 (ISSN) ; Baghani, M ; Saidi, M. H ; Sharif University of Technology
2013
Abstract
This is a theoretical study dealing with longitudinal gaseous slip flow forced convection between a periodic bunch of microcylinders arranged in regular array. The selected geometry has applications in microscale pin fin heat sinks used for cooling of microchips. The flow is considered to be hydrodynamically and thermally fully developed. The two axially constant heat flux boundary conditions of H1 and H2 are considered in the analysis. The velocity and temperature discontinuities at the boundary are incorporated into the solutions using the first order slip boundary conditions. The method considered is mainly analytical in which the governing equations and three of the boundary conditions...
Effects of preheating temperature and cooling rate on two-step residual stress in thermal barrier coatings considering real roughness and porosity effect
, Article Ceramics International ; Vol. 40, Issue. 10 , December , 2014 , pp. 15925-15940 ; ISSN: 02728842 ; Farrahi, G. H ; Azadi, M ; Ghodrati, M ; Sharif University of Technology
Abstract
In this research, a finite element model was developed in order to simulate the two-step residual stress distribution of a thermal barrier coating system, considered to be used in diesel engine cylinder head, with a real roughness and real porosity. Two steps including the bond coat and the top coat deposition processes were taken into account. The real geometry of coating layers, including the roughness and the porosity, was also considered based on a scanning electron microscopy image. Then, effects of the convective heat transfer coefficient and initial substrate and substrate/bond coat preheating temperatures on the residual stress were studied. Obtained results illustrate that the...
An experimental comparison of SiO2/water nanofluid heat transfer in square and circular cross-sectional channels
, Article Journal of Thermal Analysis and Calorimetry ; 2017 , Pages 1-10 ; 13886150 (ISSN) ; Sanjarian, N ; Kasaeian, A ; Razi Astaraei, F ; Sameti, M ; Nasirivatan, S ; Sharif University of Technology
Springer Netherlands
2017
Abstract
In this paper, with the aim of enhancing the thermal conductivity of the fluid, a nanofluid is prepared based on SiO2. A series of experimental tests were carried out for both laminar and forced convection regimes in a horizontal tube with two different geometric shapes (circular and square cross section) subjected to constant wall heat flux (4735 W m−2). A comparative study has been done to investigate the effect of the geometry on the convective heat transfer. Moreover, the effect of the volume concentration on the behavior of the nanofluid and the base fluid was evaluated by comparing various volume concentrations (0.05, 0.07 and 0.2%). The experiments were done under two different...
An experimental comparison of SiO2/water nanofluid heat transfer in square and circular cross-sectional channels
, Article Journal of Thermal Analysis and Calorimetry ; Volume 131, Issue 2 , 2018 , Pages 1577-1586 ; 13886150 (ISSN) ; Sanjarian, N ; Kasaeian, A ; Razi Astaraei, F ; Sameti, M ; Nasirivatan, S ; Sharif University of Technology
Springer Netherlands
2018
Abstract
In this paper, with the aim of enhancing the thermal conductivity of the fluid, a nanofluid is prepared based on SiO2. A series of experimental tests were carried out for both laminar and forced convection regimes in a horizontal tube with two different geometric shapes (circular and square cross section) subjected to constant wall heat flux (4735 W m−2). A comparative study has been done to investigate the effect of the geometry on the convective heat transfer. Moreover, the effect of the volume concentration on the behavior of the nanofluid and the base fluid was evaluated by comparing various volume concentrations (0.05, 0.07 and 0.2%). The experiments were done under two different...