Search for: heat-transfer-performance
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    Second law analysis of a magnetohydrodynamic plasma generator

    , Article Energy ; Volume 32, Issue 9 , 2007 , Pages 1603-1616 ; 03605442 (ISSN) Saidi, M. H ; Montazeri, A ; Sharif University of Technology
    Elsevier Ltd  2007
    The performance of an MHD generator utilizing plasma as working fluid has been assessed from the viewpoint of the second law of thermodynamics. The plasma flow in the generator linear duct has been solved by dividing the channel cross-section to an inviscid core region and the viscous boundary layers in the vicinity of the walls. The Hall effect has been taken into account and equilibrium ionization has been assumed. The dependence of the plasma properties such as Hall parameter, the coefficients of thermal and electrical conductivity, and viscosity on the plasma state has also been considered. Using the information obtained on the plasma behaviour in the generator, the entropy generation... 

    Visualization and comparative investigations of pulsating ferro-fluid heat pipe

    , Article Applied Thermal Engineering ; Volume 116 , 2017 , Pages 56-65 ; 13594311 (ISSN) Gandomkar, A ; Saidi, M. H ; Shafii, M. B ; Vandadi, M ; Kalan, K ; Sharif University of Technology
    Elsevier Ltd  2017
    Pulsating heat pipes (PHPs) are among the best solutions for the electronics cooling due to their low cost, effectiveness and being passive. Experiments to study the effective factors on heat transfer performance have been designed and as a result, improvement of ferrofluid PHP performance has been achieved. Two different heat pipes made of copper and glass were prepared to investigate the behavior of magnetic nanofluids. In order to find the best condition for heat transfer performance, different concentrations of nanofluid with a filling ratio of 50% were tested in 3 different cases of magnetic field. The results indicated that the ferrofluid is more stable in the glass PHP. It also shows... 

    The role of surface wettability on the heat transfer in liquid-liquid two-phase flow in a microtube

    , Article Physics of Fluids ; Volume 31, Issue 8 , 2019 ; 10706631 (ISSN) Moezzi, M ; Kazemzadeh Hannani, S ; Farhanieh, B ; Sharif University of Technology
    American Institute of Physics Inc  2019
    Liquid-liquid two-phase flow is capable of boosting heat transfer in microdevices compared to the single-phase and gas-liquid flows. A thorough investigation is performed here to characterize the heat transfer in water-oil flow in a microtube. Finite element method along with the level-set model is employed for numerical simulation. A main part of this paper is devoted to studying the effect of wettability on the heat transfer performance. Four contact angles of 0°, 30°, 150°, and 180° are investigated, which revealed that the contact angle of 150° produces the highest Nusselt number (Nu). Triple points form at this contact angle, and the slugs slide on the wall, which results in more... 

    A review on application of nanofluid in various types of heat pipes

    , Article Journal of Central South University ; Volume 26, Issue 5 , 2019 , Pages 1021-1041 ; 20952899 (ISSN) Nazari, M. A ; Ahmadi, M. H ; Sadeghzadeh, M ; Shafii, M. B ; Goodarzi, M ; Sharif University of Technology
    Central South University of Technology  2019
    Nanotechnology is widely used in heat transfer devices to improve thermal performance. Nanofluids can be applied in heat pipes to decrease thermal resistance and achieve a higher heat transfer capability. In the present article, a comprehensive literature review is performed on the nanofluids’ applications in heat pipes. Based on reviewed studies, nanofluids have a high capacity to boost the thermal behavior of various types of heat pipes such as conventional heat pipes, pulsating heat pipes, and thermosyphons. Besides, it is observed that there must be a selected amount of concentration for the high-performance utilization of nanoparticles; high concentration of nanoparticles causes a... 

    Effects of surface coating of nanoparticles on thermal performance of Open Loop Pulsating Heat Pipes

    , Article ASME 2012 Heat Transfer Summer Conf. Collocated with the ASME 2012 Fluids Engineering Div. Summer Meeting and the ASME 2012 10th Int. Conf. on Nanochannels, Microchannels and Minichannels, HT 2012, 8 July 2012 through 12 July 2012 ; Volume 2 , 2012 , Pages 593-599 ; 9780791844786 (ISBN) Mehdi, T ; Maziar, M ; Ali, A ; Hossein, A ; Mohammad Hassan, S ; Mohammad Behshad, S ; Siamak, K. H ; Sharif University of Technology
    Homogenous dispersing of nanoparticles in a base fluid is an excellent way to increase the thermal performance of heat transfer devices especially Heat Pipes (HPs). As a wickless, cheap and efficient heat pipe, Pulsating Heat Pipes (PHPs) are important candidates for thermal application considerations. In the present research an Open Loop Pulsating Heat Pipe (OLPHP) is fabricated and tested experimentally. The effects of working fluid namely, water, Silica Coated ferrofluid (SC ferrofluid), and ferrofluid without surface coating of nanoparticles (ferrofluid), charging ratio, heat input, and application of magnetic field on the overall thermal performance of the OLPHPs are investigated.... 

    Heat transfer on topographically structured surfaces for power law fluids

    , Article International Journal of Heat and Mass Transfer ; Volume 121 , 2018 , Pages 857-871 ; 00179310 (ISSN) Javanbakht, M. H ; Moosavi, A ; Sharif University of Technology
    Elsevier Ltd  2018
    The three-dimensional power law fluid flow through rough microchannels has been studied numerically to determine the effects of the topographic structures on the thermal and hydrodynamic characteristics of the system. Rectangular, triangular and sinusoidal element shapes have been considered in order to investigate the effects of roughness height, width, pitch and channel separation on the pressure drop and heat transfer. Uniform wall heat flux boundary condition has been applied for all the peripheral walls. The results indicate that the global heat transfer performance can be improved or reduced by the roughness elements at the expense of pressure head when compared with the smooth... 

    Lattice Boltzmann simulation of convective flow and heat transfer in a nanofluid-filled hollow cavity

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 29, Issue 9 , 2019 , Pages 3075-3094 ; 09615539 (ISSN) Pu, Q ; Aalizadeh, F ; Aghamolaei, D ; Masoumnezhad, M ; Rahimi, A ; Kasaeipoor, A ; Sharif University of Technology
    Emerald Group Publishing Ltd  2019
    Purpose: This paper aims to to simulate the flow and heat transfer during free convection in a square cavity using double-multi-relaxation time (MRT) lattice Boltzmann method. Design/methodology/approach: The double-MRT lattice Boltzmann method is used, and the natural convection fluid flow and heat transfer under influence of different parameters are analyzed. The D2Q5 model and D2Q9 model are used for simulation of temperature field and flow field, respectively. The cavity is filled with CuO-water nanofluid; in addition, the thermo-physical properties of nanofluid and the effect of nanoparticles’ shapes are considered using Koo–Kleinstreuer–Li (KKL) model. On the other hand, the cavity is... 

    Free convection analysis in a Γ-shaped heat exchanger using lattice Boltzmann method employing second law analysis and heatline visualization

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 29, Issue 9 , 2019 , Pages 3056-3074 ; 09615539 (ISSN) KhakRah, H ; Mohammaei, M ; Hooshmand, P ; Bagheri, N ; Hasani Malekshah, E ; Sharif University of Technology
    Emerald Group Publishing Ltd  2019
    Purpose: The nanofluid flow and heat transfer within a heat exchanger, with different thermal arrangements of internal active bodies, are investigated. Design/methodology/approach: For the numerical simulations, the lattice Boltzmann method is utilized. The KKL model is used to predict the dynamic viscosity of CuO-water nanofluid. Furthermore, the Brownian method is taken account using this model. The influence of shapes of nanoparticles on the heat transfer performance is considered. Findings: The results show that the platelet nanoparticles render higher average Nusselt number showing better heat transfer performance. In order to perform comprehensive analysis, the heatline visualization,... 

    Sensitivity analysis of a heat exchanger tube fitted with cross-cut twisted tape with alternate axis

    , Article Journal of Heat Transfer ; Volume 141, Issue 4 , 2019 ; 00221481 (ISSN) Nakhchi, M. E ; Esfahani, J. A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2019
    Numerical simulations are used to analyze the thermal performance of turbulent flow inside heat exchanger tube fitted with cross-cut twisted tape with alternate axis (CCTA). The design parameters include the Reynolds number (5000 < Re < 15; 000), cross-cut width ratio (0:7 < b=D < 0:9), cross-cut length ratio (2 < s=D < 2:5), and twist ratio (2 < y=D < 4). The objective functions are the Nusselt number ratio (Nu=Nus), the friction factor ratio (f =fs), and the thermal performance (g). Response surface method (RSM) is used to construct second-order polynomial correlations as functions of design parameters. The regression analysis shows that heat transfer ratio decreased with increasing both... 

    Experimental examination of utilizing novel radially grooved surfaces in the evaporator of a thermosyphon heat pipe

    , Article Applied Thermal Engineering ; Volume 169 , 2020 Bahmanabadi, A ; Faegh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2020
    The application of heat pipes with flat evaporators in cooling electronic devices has attracted a lot of attention in recent years. Increasing the rate of heat transfer in their evaporator by utilizing structured surfaces is considered as a prominent method for reducing the thermal resistance of the heat pipes. In this study, the performance of a thermosyphon heat pipe with novel radially rectangular-grooved and radially inclined triangular-grooved evaporator surfaces was evaluated experimentally. It is hypothesized that the radial grooves may enhance the performance by inducing rotational motions and increasing the heat transfer coefficients. Based on the results, the optimum filling ratio... 

    Heat transfer hybrid nanofluid (1-Butanol/MoS2–Fe3O4) through a wavy porous cavity and its optimization

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; 2020 Hosseinzadeh, K ; Montazer, E ; Shafii, M. B ; Ganji, D. D ; Sharif University of Technology
    Emerald Group Holdings Ltd  2020
    Purpose: The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles. Design/methodology/approach: The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite... 

    Numerical study of heat transfer between shell-side fluid and shell wall in the spiral-wound heat exchangers

    , Article International Journal of Refrigeration ; Volume 120 , December , 2020 , Pages 285-295 Mostafazade Abolmaali, A ; Afshin, H ; Sharif University of Technology
    Elsevier Ltd  2020
    Heat transfer between heat exchangers and the surrounding environment, referred to as heat-in-leak, is a crucial phenomenon in the cryogenic applications which can substantially degrade the heat exchanger performance. Present research is organized to investigate the mechanism of heat transfer between the shell-side fluid and the shell wall of spiral wound heat exchangers (SWHEs) to determine the heat transfer coefficient used in the heat-in-leak calculations. The heat transfer characteristics are studied using computational fluid dynamics (CFD) tools. First, 20 dissimilar SWHE models with respect to the geometrical parameters are built and then numerically simulated at different Reynolds... 

    Thermo-hydraulic performance enhancement of nanofluid-based linear solar receiver tubes with forward perforated ring steps and triangular cross section; a numerical investigation

    , Article Applied Thermal Engineering ; Volume 169 , March , 2020 Mahmoudi, A ; Fazli, M ; Morad, M. R ; Gholamalizadeh, E ; Sharif University of Technology
    Elsevier Ltd  2020
    Cylindrical pipes are installed to a line-focusing solar system with a linear receiver tube for transmitting thermal energy to the working fluid. In this study, the effects of a novel forward ring step inside circular pipes on the heat transfer performance of linear solar receiver tubes were investigated using computational fluid dynamics. The rings are perforated, and their cross section is triangular. Although the applied heat flux is consistent with a solar collector with a linear receiver tube, the analysis can be performed for any given heat flux distribution on circular pipes. The model was verified by comparing the predicted Nusselt numbers to those of the Gnielinski correlation, and... 

    Computational analysis of nanofluid effects on convective heat transfer enhancement of micro-pin-fin heat sinks

    , Article International Journal of Thermal Sciences ; Volume 58 , 2012 , Pages 168-179 ; 12900729 (ISSN) Seyf, H. R ; Feizbakhshi, M ; Sharif University of Technology
    Elsevier  2012
    Numerical investigation on the application of nanofluids in Micro-Pin-Fin Heat Sinks (MPFHSs) has been presented in this paper. To investigate flow and heat transfer behavior in MPFHS the three-dimensional steady Navier-Stokes and energy equations were discretized using a finite volume approach and have been solved iteratively, using the SIMPLE algorithm. DI-water is used as a base coolant fluid while the nanoparticles used in the present study are CuO nanoparticles with mean diameters of 28.6 and 29 nm and Al 2O 3 nanoparticles with mean diameters of 38.4 and 47 nm. The results show that (i) a significant enhancement of heat transfer in the MPFHS due to suspension of CuO orAl 2O 3... 

    Comparison of performance prediction of solar water heaters between artificial neural networks and conventional correlations

    , Article International Journal of Global Energy Issues ; Volume 31, Issue 2 , 2009 , Pages 122-131 ; 09547118 (ISSN) Razavi, J ; Riazi, M. R ; Raoufi, F ; Sadeghi, A ; Sharif University of Technology
    The aim of this study was to develop a predictive method for heat transfer coefficients in solar water heaters and their performance evaluation of such heaters with different materials used as heat collectors. Two approaches have been used: conventional method and an Artificial Neural Network (ANN) to predict the performance of solar water heaters and to compare these two approaches. This performance is measured in terms of outlet temperature by using a set of conventional feed forward multi-layer neural networks. The actual experimental data which were used as our network's input gathered from published literature (for polypropylene tubes) and from the experiments carried out recently using... 

    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 Montazer, E ; 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
    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... 

    Thermo-mechanical modeling of high speed spindles

    , Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 282-293 ; 10263098 (ISSN) Zahedi, A ; Movahhedy, M. R ; Sharif University of Technology
    Prediction of the thermo-mechanical behavior of machine-tool spindles is essential in the reliable operation of high speed machine tools. In particular, the performance of these high speed spindles is dependent on their thermal behavior. The main source of heat generation in the spindle is the friction torque in angular contact ball bearings. This paper presents an effort to develop a comprehensive model of high speed spindles that includes viable models for the mechanical and thermal behavior of its major components, i.e., bearings, shaft and housing. Spindle housing and shaft are treated as six-degree-of-freedom Timoshenko beam elements. Bearings are modeled as two-node elements with five...