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convective-heat-transfer-coefficient
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Experimental study on convective heat transfer coefficient around a vertical hexagonal rod bundle
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 48, Issue 6 , 2012 , Pages 1023-1029 ; 09477411 (ISSN) ; Sharif University of Technology
2012
Abstract
Research on convective heat transfer coefficient around a rod bundle has many diverse applications in industry. So far, many studies have been conducted in correlations related to internal and turbulent fully-developed flow. Comparison shows that Dittus-Boelter, Sieder-Tate and Petukhov have so far been the most practical correlations in fully-developed turbulent fluid flow heat transfer. The present study conducts an experimental examination of the validity of these frequently-applied correlations and introduces a manufactured test facility as well. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) can fulfil...
Experimental study of forced convection heat transfer from a cam shaped tube in cross flows
, Article International Journal of Heat and Mass Transfer ; Volume 50, Issue 13-14 , 2007 , Pages 2605-2611 ; 00179310 (ISSN) ; Lavasani, A. M ; Sharif University of Technology
2007
Abstract
An experimental investigation has been conducted to clarify forced convection heat transfer characteristic and flow behavior of an isothermal cam shaped tube in cross flow. The range of angle of attack and Reynolds number based on an equivalent circular tube are within 0° < α < 180° and 1.5 × 104 < Reeq < 2.7 × 104, respectively. The results show that the mean heat transfer coefficient is a maximum at about α = 90° over the whole range of the Reynolds numbers. It is found that thermal hydraulic performance of the cam shaped tube is larger than that of a circular tube with the same surface area except for α = 90° and 120°. Furthermore, the effect of the diameter of the cam shaped tube upon...
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...
Performance optimization of solar chimney power plant using electric/corona wind
, Article Journal of Electrostatics ; Volume 78 , 2015 , Pages 22-30 ; 03043886 (ISSN) ; Kasaeian, A ; Ghalamchi, M ; Ghalamchi, M ; Sharif University of Technology
Elsevier
2015
Abstract
The effect of the corona wind on the natural convection at absorber of a solar chimney power plant pilot was investigated experimentally. The aim of the study is to improve the efficiency of SCPP through enhanced the heat transfer coefficient of absorber with corona wind. The results show that corona wind enhanced the absorber convective heat transfer coefficient leading to increment in air the velocity and the output power of the SCPP. The amount of heat transfer of pilot increased more than 14.5% when applying voltage of 15 KV and the speed in chimney experienced about 72% amelioration
Experimental assessment of convective heat transfer coefficient enhancement of nanofluids prepared from high surface area nanoporous graphene
, Article International Communications in Heat and Mass Transfer ; Volume 78 , 2016 , Pages 127-134 ; 07351933 (ISSN) ; Sattari, S ; Rashidi, A. M ; Sharif University of Technology
Elsevier Ltd
Abstract
In this research convective heat transfer coefficient enhancement of nanofluids prepared from high surface area graphene has been investigated in laminar flow in the developing region. The nanofluid has been prepared from nanoporous graphene with high surface area and with concentration of 0.025 to 0.1 wt.%. Deionized water has been used as the base fluid and a type of Ter-Polymer has been utilized as the surfactant. The results indicate that thermal conductivity of nanofluid with concentration of 0.1 wt.% remains quite constant, with only 3.8% enhancement, while convective heat transfer coefficient improves significantly, with 34% enhancement. The behavior of this enhancement related to the...
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....
Two-dimensional numerical investigation of a micro combustor
, Article Scientia Iranica ; Volume 17, Issue 6 B , December , 2010 , Pages 433-442 ; 10263098 (ISSN) ; Saidi, M. S ; Saidi, M. H ; Shafii, M. B ; Sharif University of Technology
2010
Abstract
In this paper, a two-dimensional numerical approach is used to study the effect of micro combustor height, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry is used. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system that leads to two stiff systems of PDEs. In the present work, the computational domain is solved through the Strang splitting method, which is suitable for a nonlinear stiff system of PDEs. A revised boundary condition for the velocity equation is applied and its effect on the flow...
Experimental investigation on laminar forced convection heat transfer of ferrofluids under an alternating magnetic field
, Article Experimental Thermal and Fluid Science ; Volume 49 , 2013 , Pages 193-200 ; 08941777 (ISSN) ; Dibaei, M. H ; Hakim Sima, A ; Shafii, M. B ; Sharif University of Technology
2013
Abstract
This research study presents an experimental investigation on forced convection heat transfer of an aqueous ferrofluid flow passing through a circular copper tube in the presence of an alternating magnetic field. The flow passes through the tube under a uniform heat flux and laminar flow conditions. The primary objective was to intensify the particle migration and disturbance of the boundary layer by utilizing the magnetic field effect on the nanoparticles for more heat transfer enhancement. Complicated convection regimes caused by interactions between magnetic nanoparticles under various conditions were studied. The process of heat transfer was examined with different volume concentrations...
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...
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...
One-dimensional numerical investigation of a cylindrical micro combustor
, Article Proceedings of the ASME Summer Heat Transfer Conference 2009, HT2009 ; Volume 3 , 2009 , Pages 115-123 ; 9780791843581 (ISBN) ; Saediamiri, M ; Saidi, M. S ; Saidi, M. H ; Shafii, M. B ; Sharif University of Technology
Abstract
In this paper, a one-dimensional numerical approach is used to study the effect of various parameters such as micro combustor diameter, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used and thermal conductivity of the mixture is considered as a function of species thermal conductivity and temperature by using a set of new relations. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system (A-D-R) that leads to two stiff systems of PDEs, which can not be solved by...
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...
Nitrogen-doped carbon nanotubes for heat transfer applications: Enhancement of conduction and convection properties of water/N-CNT nanofluid
, Article Journal of Thermal Analysis and Calorimetry ; Volume 138, Issue 1 , 2019 , Pages 69-79 ; 13886150 (ISSN) ; Askari, S ; Ghasemy, E ; Rashidi, A ; Ettefaghi, E ; Sharif University of Technology
Springer Netherlands
2019
Abstract
In this research, it is aimed to enhance the heat transfer properties of the carbon nanotubes through nitrogen doping. To this end, nitrogen-doped multiwall carbon nanotubes (N-CNTs) were synthesized via chemical vapor deposition method. For supplying carbon and nitrogen during the synthesis of N-CNTs, camphor and urea were used, respectively, at 1000 °C over Co–Mo/MgO nanocatalyst in a hydrogen atmosphere. N-CNTs with three different nitrogen loadings of 0.56, 0.98, and 1.38 mass% were synthesized, after which, water/N-CNT nanofluids of these three samples with concentrations of 0.1, 0.2, and 0.5 mass% were prepared. To obtain a stable nanofluid, N-CNTs were functionalized by nitric acid...
Heat transfer in turbulent nanofluids: separation flow studies and development of novel correlations
, Article Advanced Powder Technology ; Volume 31, Issue 8 , August , 2020 , Pages 3120-3133 ; Shafii, M. B ; Salami, E ; Muhamad, M. R ; Yarmand, H ; Gharehkhani, S ; Chowdhury, Z. Z ; Kazi, S. N ; Badarudin, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Convective heat transfer plays a significant role in numerous industrial cooling and heating applications. This method of heat transfer can be passively improved by reconfiguring flow passage, fluid thermophysical properties, or boundary conditions. The broader scope of nanotechnology introduced several studies of thermal engineering and heat transfer. Nano-fluids are one of such technology which can be thought of engineered colloidal fluids with nano-sized particles. In the present study, turbulent forced convection heat transfer to nanofluids in an axisymmetric abrupt expansion heat exchanger was investigated experimentally. During heat transfer investigation, the functionalized...