Search for: heat-transfer
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    Heat transfer between micro- and nano-mechanical systems through optical channels

    , Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 7 , 2014 , pp. 1525-1532 ; ISSN: 07403224 Farman, F ; Bahrampour, A. R ; Sharif University of Technology
    In this paper, a new mechanism of heat transfer is introduced. It is shown that, without emission and absorption of photons, light can operate as a channel of heat transfer between nano- or micro-mechanical oscillators. We consider the dynamics of two vibrating mirrors coupled through one optical cavity mode in an optomechanical system. It is shown that light mediates heat transfer between two micro-mirrors. When the detuning frequency of the mechanical resonators is low, fluctuations flow through the light channel from the high temperature vibrating mirror toward the low temperature one. This behavior is named the resonance heat transfer effect. The rate of heat flow between the mechanical... 

    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) Makhmalbaf, M. H. M ; Sharif University of Technology
    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 research on heat transfer of water in tubes with conical ring inserts in transient regime

    , Article International Communications in Heat and Mass Transfer ; Volume 38, Issue 5 , 2011 , Pages 668-671 ; 07351933 (ISSN) Anvari, A. R ; Lotfi, R ; Rashidi, A. M ; Sattari, S ; Sharif University of Technology
    Forced convective of water in horizontal tubes with conical tube inserts has been studied experimentally. The transient flow regime has been used for the tests. Experimental results are validated with existing well established correlation. The turbulators were placed in two different arrangements: converging conical ring, referred to as CR array and diverging conical ring, DR array. Two correlations for the Nusselt number based on the experiment are introduced for practical use. It is found that the insertion of turbulators has enhanced the Nusselt number for the DR arrangement up to 521%, and for the CR arrangement up to 355%, although using the turbulators cause a significant increase in... 

    Advances in non-gray radiation calculation in combusting environments using a modified reference approach

    , Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 54, Issue 9 , 2018 , Pages 2705-2713 ; 09477411 (ISSN) Darbandi, M ; Abrar, B ; Sharif University of Technology
    Springer Verlag  2018
    The radiative heat transfer should be calculated very accurately in many combustion domains. This work uses the spectral-line based weighted-sum-of-gray-gases (SLW) model to calculate the radiation heat transfer in a model furnace representing a combustion field with high temperature gradient variations. The past researchers have commonly implemented the reference approach in the SLW model. However, the reference approach produces error because of enforcing a reference temperature to perform the non-gray radiation heat transfer calculations in non-isothermal domains. In this work, we implement a modified reference approach, which reduces such errors in non-gray gas calculations. We show that... 

    Experimental and numerical investigation of the effect of laser input energy on the mechanical behavior of stainless steel and polyamide joint in the LAMP joining method

    , Article International Journal of Advanced Manufacturing Technology ; Volume 113, Issue 11-12 , 2021 , Pages 3585-3597 ; 02683768 (ISSN) Ghanavati, R ; Ranjbarnodeh, E ; Shoja Razavi, R ; Pircheraghi, G ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    The present study investigated the effect of laser input energy on the quality and mechanical behavior of a 304 stainless steel–polyamide 6 joint in the laser-assisted metal and polymer direct joining (LAMP) method experimentally and numerically. After the proposed heat transfer model was validated, it was determined whether there was an optimal amount of laser input energy that could produce a joint with favorable quality and mechanical behavior. Among different laser input energies used in this study, 28-J/mm energy can provide more uniform and extensive wetting of the metal surface by the polymer, while excessive polymer degradation in the joint zone was prevented. As a result, an optimal... 

    Analysis of fluid flow and heat transfer in microchannels using combined pressure gradient and electroosmotic pumping

    , Article 3rd International Conference on Microchannels and Minichannels, ICMM2005, Toronto, ON, 13 June 2005 through 15 June 2005 ; Volume PART A , 2005 , Pages 503-510 ; 0791841855 (ISBN) Monazarami, R ; Zade, A. Q ; Manzari, M. T ; Sharif University of Technology
    A numerical model has been developed for studying the flow and heat transfer characteristics of single phase liquid flow through a microchannel. In this work the heat transfer characteristics of pressure driven and electroosmotic flow through microchannels have been studied. The governing equations are the Poisson-Boltzmann and Navier-Stokes equations which have been solved numerically using the standard Galerkin and the Mixed 4-1 finite element methods, respectively. Finally the energy equation is solved numerically using the Stream-wise Upwind Petrov Galerkin (SUPG) method. Two dimensional Poisson-Boltzmann equation was first solved to find the electric potential field and net charge... 

    Transient heat transfer analysis of a layer by considering the effect of radiation

    , Article Journal of Fusion Energy ; Volume 23, Issue 3 , 2005 , Pages 207-215 ; 01640313 (ISSN) Sharbati, E ; Safavisohi, B ; Aghanajafi, C ; Sharif University of Technology
    The transient heat transfer analysis of a layer has been studied much less than the steady state. However, transient temperature distribution resulted from including radiation and conduction simultaneously, is significantly different from those obtained by considering conduction alone. In order to include the effect of radiation heat transfer, we must insert the gradient of radiative flux in the energy equation. For this purpose, a variety of multi-flux methods have been suggested. A simplified procedure is the two-flux method, which is the one used in the present paper. This paper is focused on one-dimensional transient heat transfer of a layer using Finite Difference Method. To this end, a... 

    , M.Sc. Thesis Sharif University of Technology Shokrani, Mohammad (Author) ; Dolati, Abolghasem (Supervisor)
    In recent years, different of nanoparticles as oil additives has been investigated in many studies . These research show that nanoparticles are deposited on the surface friction and improve tribology properties of base oil and also significant reduction of wear and friction caused by the nanoparticles. Compared with metal and metal oxide nanoparticles , carbon nanotubes (CNT) due to the high thermal conductivity and high aspect ratio , is an excellent candidate as the nanoparticle is dispersed . For preparing useful oil it is essential to stabilize nanoparticles in fluid that will not settle over long time . Oils containing nanoparticles by increasing the heat transfer coefficient... 

    Modeling and Simulation of Magnetic Nanofluids Convective Heat Transfer around a Sphere in the Presence of External Magnetic Feild

    , M.Sc. Thesis Sharif University of Technology Abbasi, Zeinab (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    The good performance in cooling, especially in systems with small dimensions, is one of the critical needs of many industries. Heat transfer around sphere in all systems that contain particles, is important. Many methods have been proposed to improve the heat transfer rate but using nanofluids is one of the ways that has attracted more attention than others. Ferrofluids have magnetic properties in addition to nanofluids properties and this has a significant impact in increasing the heat transfer rate. Controlling heat transfer by magnetic field is one of the unique characteristics of this fluid. The project aim is to investigate the effect of magnetic field on heat transfer around sphere in... 

    Effect of pressure on heat transfer coefficient at the metal/mold interface of A356 aluminum alloy

    , Article International Communications in Heat and Mass Transfer ; Volume 39, Issue 5 , 2012 , Pages 705-712 ; 07351933 (ISSN) Fardi Ilkhchy, A ; Jabbari, M ; Davami, P ; Sharif University of Technology
    The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of casting under different pressures were obtained using the inverse heat conduction problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented for correlation between external pressure and heat transfer coefficient. Acceptable... 

    Evaluation of pressure effect on heat transfer coefficient at the metal-mold interface for casting of A356 al alloy

    , Article Iranian Journal of Materials Science and Engineering ; Volume 9, Issue 1 , 2012 , Pages 11-20 ; 17350808 (ISSN) Fardi Ilkhchy, A ; Varahraam, N ; Davami, P ; Sharif University of Technology
    During solidification and casting in metallic molds, the heat flow is controlled by the thermal resistance at the casting-mold interface. Thus heat transfer coefficient at the metal-mold interface has a predominant effect on the rate of heat transfer. In some processes such as low pressure and die-casting, the effect of pressure on molten metal will affect the rate of heat transfer at least at initial steps of solidification. In this study interfacial heat transfer coefficient at the interface between A356 alloy casting and metallic mold during the solidification of casting under pressure were obtained using the IHCP (Inverse Heat Conduction Problem) method. Temperature measurements are then... 

    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) Zamzamian, A ; Oskouie, S. N ; Doosthoseini, A ; Joneidi, A ; Pazouki, M ; Sharif University of Technology
    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... 

    Pool boiling heat transfer in dilute water/triethyleneglycol solutions

    , Article Chinese Journal of Chemical Engineering ; Volume 17, Issue 4 , 2009 , Pages 552-561 ; 10049541 (ISSN) Alavi Fazel, S. A ; Safekordi, A. A ; Jamialahmadi, M ; Sharif University of Technology
    Boiling of water/triethyleneglycol (TEG) binary solution has a wide-ranging application in the gas processing engineering. Design, operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution. In this investigation, nucleate pool boiling heat transfer coefficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition. The present experimental data are correlated using major existing correlations. In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which... 

    Optimization of the heat transfer coefficient and pressure drop of Taylor-Couette-Poiseuille flows between an inner rotating cylinder and an outer grooved stationary cylinder

    , Article International Journal of Heat and Mass Transfer ; Volume 108 , 2017 , Pages 1449-1459 ; 00179310 (ISSN) Nouri Borujerdi, A ; Nakhchi, M. E ; Sharif University of Technology
    Elsevier Ltd  2017
    The aim of this study is to find optimum values of design parameters of annular flow with outer grooved cylinder and rotating inner cylinder in the presence of axial flow by using Response surface Method (RSM). This configuration is popular in cooling of electric generators and rotating machineries. Groove aspect ratio (0

    Advanced heat transfer analysis of a U-shaped pulsating heat pipe considering evaporative liquid film trailing from its liquid slug

    , Article Applied Thermal Engineering ; Volume 138 , 28 June , 2018 , Pages 475-489 ; 13594311 (ISSN) Nemati, R ; Behshad Shafii, M ; Sharif University of Technology
    Elsevier Ltd  2018
    In order to study the heat transfer mechanism and predict the heat transfer capability of a pulsating heat pipe (PHP), a numerical model was used to simulate the oscillating behavior of liquid slug considering liquid film thickness in the evaporator and reduction of liquid film thickness due to evaporation. In this article, thermal performance of an open loop closed end PHP of copper with a diameter of 1 mm and various working fluids including water (DW) and ethanol was investigated. The governing equations of mass, momentum, and energy equations were solved for liquid slug and vapor plugs. The results showed that by considering liquid film thickness behind the liquid slug, for both the... 

    Investigation of the combination of TiO2 nanoparticles and drag reducer polymer effects on the heat transfer and drag characteristics of nanofluids

    , Article Canadian Journal of Chemical Engineering ; Volume 96, Issue 6 , 2018 , Pages 1430-1440 ; 00084034 (ISSN) Paryani, S ; Ramazani Ahmad, S. A ; Sharif University of Technology
    Wiley-Liss Inc  2018
    To compensate for drag increment due to the addition of nanoparticles to heat-transfer fluids, it seems that one could add drag reducer polymeric agents to these fluids. So, in this work, experiments were carried out for solutions of two types of polyacrylamide (FLOPAAM 3330S and FLOPAAM 3630S) at three distinct concentrations (25, 40, and 55 ppm), and TiO2-water nanofluid at concentrations of 0.015, 0.02, 0.025, and 0.03 L/L. The steady state turbulent convective heat transfer and the friction factor of the suspension of TiO2 in a dilute solution of very high molecular weight, polyacrylamide (hybrid fluid), in a coiled tube were analyzed. Experimental measurements were carried out from a... 

    Solution of thermally developing zone in short micro-/nanoscale channels

    , Article Journal of Heat Transfer ; Volume 131, Issue 4 , 2009 , Pages 44501-1- 44501-5 ; 00221481 (ISSN) Darbandi, M ; Vakilipour, S ; Sharif University of Technology
    We numerically solve the Navier-Stokes equations to study the rarefied gas flow in short micro- and nanoscale channels. The inlet boundary conditions play a critical role in the structure of flow in short channels. Contrary to the classical inlet boundary conditions, which apply uniform velocity and temperature profiles right at the real channel inlet, we apply the same inlet boundary conditions, but at a fictitious position far upstream of the real channel inlet. A constant wall temperature incorporated with suitable temperature jump is applied at the channel walls. Our solutions for both the classical and extended inlet boundary conditions are compared with the results of other available... 

    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) Bazmi, M ; Askari, S ; Ghasemy, E ; Rashidi, A ; Ettefaghi, E ; Sharif University of Technology
    Springer Netherlands  2019
    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... 

    Unsteady natural convection in a differentially heated rectangular enclosure possessing sinusoidal corrugated side walls loaded with power law non-newtonian fluid

    , Article Fluid Dynamics ; Volume 54, Issue 2 , 2019 , Pages 159-176 ; 00154628 (ISSN) Salehpour, A ; Abdolahi Sadatlu, M. A ; Sojoudi, A ; Sharif University of Technology
    Pleiades Publishing  2019
    This research is a numerical analysis exhaustively investigating two-dimensional (2D) transient convective heat transfer in a differentially heated rectangle, possessing sinusoidal corrugated side walls at constant temperatures. The quadrilateral space is filled with a power-law non-Newtonian fluid, plus the right and left walls are uniformly cooled and heated, respectively. The top and bottom walls are retained as adiabatic and the side walls are recast exploiting sinusoidal corrugated shape. The governing equations of the problem are solved using the finite volume method. The evaluation of fluid flow and heat transfer is conducted in such a manner that the power law index n varies from 0.6... 

    Energetic and exergetic performance enhancement of heat exchangers via simultaneous use of nanofluid and magnetic swirling flow: A two-phase approach

    , Article Thermal Science and Engineering Progress ; Volume 20 , 2020 Bezaatpour, M ; Rostamzadeh, H ; Sharif University of Technology
    Elsevier Ltd  2020
    A high-efficient method has been considered for simultaneously improving the hydrothermal and exergetic performance of heat exchangers. Two-phase Eulerian model is employed in a 3-D numerical study to precisely study the hydrothermal and entropic behaviors of Fe3O4/water ferrofluid, under the effect of a magnetic field inducer. The findings reveal that employing the magnetic field can improve the energetic and exergetic performance by generating a swirling flow in the heat exchanger. The pressure drop and entropy generation minimization are also achieved by the induced flow in comparison with other passive techniques due to the lack of any additional obstacle in the flow path. Results show...