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heat-transfer-enhancement
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Heat transfer enhancement in shell-and-tube heat exchangers using porous media
, Article Heat Transfer Engineering ; Volume 36, Issue 3 , 2015 , Pages 262-277 ; 01457632 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
A numerical simulation has been carried out to investigate the heat transfer enhancement in a shell-and-tube heat exchanger using a porous medium inside its shell and tubes, separately. A three-dimensional geometry with k-ε turbulent model is used to predict the heat transfer and pressure drop characteristics of the flow. The effects of porosity and dimensions of these media on the heat exchanger's thermal performance and pressure drop are analyzed. Inside the shell, the entire tube bundle is wrapped by the porous medium, whereas inside the tubes the porous media are located in two different ways: (1) at the center of the tubes, and (2) attached to the inner wall of the tubes. The results...
Investigation of heat transfer enhancement in a microchannel heat sink with the aid of internal fins: a metamodel approach
, Article Computer Aided Chemical Engineering ; Volume 48 , 2020 , Pages 85-90 ; Kazemeini, M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Heat transfer enhancement with microchannel tools has been increased in recent year. In this study effect of geometric parameters as well as Reynolds number have been studied with experimental design approach. A metamodel was generated in this study for pressure drop and average Nusselt number passed all statistical tests. Order of an individual effect upon a response has been evaluated and interaction effects have been determined. Numerical results indicated that heat transfer increased significantly with inserting pyramidal micro fins. © 2020 Elsevier B.V
Experimental of Convective Heat Transfer Coefficient Around a Vertical Rod Bundle
, M.Sc. Thesis Sharif University of Technology ; Jafari, Jalil (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
Research on convective heat transfer coefficient around a rod bundle has several applications in industry. So far, many studies have been conducted in correlations related to internal fully developed flow. By comparing Dittus-Boelter, Sieder-Tate and Petukhov found to be more practical. The present study examines the validity of these frequently applied correlations experimentally. A thermohydraulic loop has been designed and manufactured to test and measuring the convective heat transfer coefficient. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) has achieved extensive application. The major deviation factors...
Experimental Investigation on Laminar Forced Convection Heat Transfer of Ferrofluids Under an Alternating Magnetic Field
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
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...
Heat Transfer Enhancement in Shell-and-Tube Heat Exchangers Using Porous Media
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
Heat transfer enhancement in heat transfer equipment, such as heat exchangers, has been widely studied. There are plenty of techniques to increase heat transfer in tubular heat exchangers. One of these techniques is applying a porous medium. These media have a great interface with fluids which can enhance the heat transfer rate. Meanwhile, the thermal conductivity of these media is usually greater than that of the studied fluid. Thus, by adding a kind of highly conductive porous insert to a heat exchanger, we are able to save the material used to construct the device and the space occupied by it.
Shell-and-tube heat exchangers are one of the most widely-used types of exchangers in...
Shell-and-tube heat exchangers are one of the most widely-used types of exchangers in...
Numerical Study of Passive Heat Transfer Enhancement Methods in Automobile Radiator
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor)
Abstract
In this study, a three dimensional model of water-ethylene glycol based aluminum oxide nanofluid in the laminar flow of an automobile radiator has been numerically studied. The passive heat transfer enhancement method of twisted tape insertion in the flat tubes of radiator is used. The effects of different parameters on heat transfer and pressure drop have been investigated. Simulation results show that utilizing twisted tapes is an effective way of enhancing heat transfer in an automobile radiator. Despite the pressure drop penalty of using twisted tapes, the thermal performance factor which is a proper criteria for evaluating the practical use of the twisted tapes and considers the effect...
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) ; Lotfi, R ; Rashidi, A. M ; Sattari, S ; Sharif University of Technology
2011
Abstract
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...
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) ; Zade, A. Q ; Manzari, M. T ; Sharif University of Technology
2005
Abstract
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...
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...
Developing a metamodel based upon the DOE approach for investigating the overall performance of microchannel heat sinks utilizing a variety of internal fins
, Article International Journal of Heat and Mass Transfer ; Volume 149 , 2020 ; Kazemeini, M ; Rashidi, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, the effects of geometry and operating conditions upon the thermal and hydraulic performance of Finned Microchannel Heat Sink (FMCHS) were investigated. Water and aluminum were considered as fluid and solid for the computational domain (30 mm × 0.8 mm × 0.8 mm). The Microchannel (MC) was supposed to have 0.65 mm height with an aspect ratio of 0.5. CFD analysis was applied for the assessments of four-types of micro-fins (i.e., conical, pyramidal, cylindrical and cubical). In order to evaluate the effects of height, diameter, the spacing of fins and Reynolds number on the overall performance of FMCHS, central composite design at five levels was used to generate design points....
Experimental Investigation on Forced Convection Heat Transfer of Ferrofluids under an Alternating Magnetic Field
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
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 a magnetic field. Both constant magnetic field and alternating magnetic field was examined. Moreover magnetic field layout and strength and modes of alternating magnetic field was investigated. 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...
Visualization and Investigation of The Influence of the Connecting Channels on Flat-Plate Pulsating Heat-Pipes’ Heat-Transfer
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
Abstract
A desired circulatory flow in flat-plate pulsating heat-pipes may improve electronic thermal management. This desired flow can be achieved by fabricating connecting channels (CCs) to increase flow resistance in one direction. In addition, connecting channels may increase the freedom degree of fluid. In order to investigate the effect of CC, two aluminum flat plate thermal spreaders with overall size 320mm×220mm×5mm - one with CC (CC-FPHP) and one without it- were fabricated. Both of the speaders have square channels with crosssection 2mm×2.8mm. The FPHPs were charged with ethanol as working fluid with filling ratios of 35%, 50%, 65%, and 80% by volume. Performance of connecting-channels in...
Experimental Investigation ofClosed-loop Pulsating Heat-pipe with an Additional Branch in the Evaporator Section
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
Abstract
The main idea of this investigation is to increase heat transfer rate by increasing flow circulation of working fluid. By placing additional branches in the evaporator section, secondary bubble pumps were created which improved the circulation of fluid inside PHP. This research was implemented in two distinct phases. In the first phase, the novelty was implemented on a single turn PHP and in the second phase, the same procedure was implemented on a 4-turn PHP. In order to investigate the impact of these additional branches, two similar heat pipes were fabricated. One of them was the conventional PHP and the other had additional branches and is named additional branch PHP (AB-PHP). Thermal...
Experimental Investigation of Convective Heat Transfer and Pressure Loss in a Circular Tube With Suspeded Ball Turbulators
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
Abstract
Flow turbulators have crucial importance in heat transfer and energy harvesting applications. Therefore, in this study, the thermo-hydraulic and vibrational behavior of the floe inside a circular tube with vibrational ball turbulators (VBTs) on an axial elastic wire is experimentally studied for the first time. In this novel design, the elastic wire facilitates turbulence by allowing VBTs to move transversally and rotationally and agitate the flow substantially. The effects of diameter and longitudinal distance (pitch) ratios of VBTs, the Reynolds number, and the axial tension of the wire, on the flow friction factor (f), the Nusselt number (Nu), the thermal performance factor (η), in...
Numerical study of enhanced heat transfer by coupling natural and electro-convections in a horizontal enclosure
, Article Journal of Enhanced Heat Transfer ; Volume 18, Issue 6 , 2011 , Pages 503-511 ; 10655131 (ISSN) ; Saidi, M. S ; Saidi, M. H ; Sharif University of Technology
2011
Abstract
The heat transfer enhancement of natural convection using an electrohydrodynamic technique inside a horizontal enclosure heated from below is studied numerically. The interactions between the electric field, flow field, and temperature field are investigated by computational fluid dynamics methods. The flow and temperature fields are affected by voltage applied to the wire electrodes. For different voltages and numbers of electrodes, it is noticed that the Nusselt number increases in all cases and the best enhancement is obtained at lower Rayleigh numbers. It is also shown that increasing the number of electrodes does not always cause an increase in the heat transfer enhancement. Actually,...
Simulation of thermally developing laminar ow in partially filled porous pipes under wall suction
, Article Scientia Iranica ; Volume 23, Issue 6 , 2016 , Pages 2641-2649 ; 10263098 (ISSN) ; Seyyed Hashemi, M. H ; Sharif University of Technology
Sharif University of Technology
Abstract
This study numerically investigates uid ow and heat transfer enhancement of a two-dimensional developing laminar ow in an axisymmetric pipe with partially filled porous material attached to the wall. The effects of porous layer in the range of 0 ≤ δ=R < 1 and Darcy number in the range of 10-6 ≤ Da ≤ 10-4 are investigated. It is found that thermal entrance length increases with porous layer thickness and is longer than a plain pipe. In addition, the dependence of Nusselt number on the thickness of the porous layer is not monotonic. A critical value of the porous layer thickness exists at which the Nusselt number value reaches the minimum. As the porous layer is thickening, more uid is pushed...
Electrode arrangement effect on natural convection in a horizontal enclosure
, Article ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels ; Issue PART A , 2009 , Pages 187-196 ; 9780791843499 (ISBN) ; Saidi, M. S ; Saidi, M. H ; ASME ; Sharif University of Technology
Abstract
The heat transfer enhancement of natural convection, using electrohydrodynamic technique inside a horizontal enclosure heated from below, is studied numerically. The interactions between electric field, flow field, and temperature field are investigated by CFD methods. The flow and temperature fields are affected by voltage applied at the wire electrodes. For different voltages and number of electrodes, it is noticed that the Nusselt number increased in all cases and the best enhancement is obtained at lower Rayleigh numbers. It is also shown that increasing the number of electrodes doesn't always cause an increase in the heat transfer enhancement. Actually, when the number of electrodes is...
Heat transfer enhancement in annular flow with outer grooved cylinder and rotating inner cylinder: review and experiments
, Article Applied Thermal Engineering ; Volume 120 , 2017 , Pages 257-268 ; 13594311 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Abstract
This experimental work is an attempt to identify the most significant parameters influencing heat transfer enhancement in annular flow with outer grooved cylinder and rotating inner cylinder. This type of flow known as Taylor-Couette flow has many industrial applications such as electrical power generators and rotating machineries. A comprehensive review of the previous works on flow regimes, heat transfer and pressure drop in grooved channels is provided. The experiments are conducted based on four different factors including Taylor number, 0
Experimental investigation of graphene oxide nanofluid on heat transfer enhancement of pulsating heat pipe
, Article International Communications in Heat and Mass Transfer ; Volume 91 , February , 2018 , Pages 90-94 ; 07351933 (ISSN) ; Ghasempour, R ; Ahmadi, M. H ; Heydarian, G ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Pulsating heat pipes (PHPs) are heat transfer devices which are widely utilized in electronic devices and energy systems. Improvement in thermal performance of PHPs will lead to higher heat transfer capacity and enhancement in the efficiency of systems which PHPs are applied. In this study, an experimental investigation was performed on the thermal performance of a pulsating heat pipe by applying graphene oxide nanofluid as working fluid. Four concentrations of graphene oxide (0.25, 0.5, 1, and 1.5 g/lit) in water as base fluid were used in the PHP. Results indicate that adding graphene oxide sheets increased thermal conductivity and viscidity of the base fluid. Moreover, utilizing graphene...
Numerical investigation of different geometrical parameters of perforated conical rings on flow structure and heat transfer in heat exchangers
, Article Applied Thermal Engineering ; Volume 156 , 2019 , Pages 494-505 ; 13594311 (ISSN) ; Esfahani, J. A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
A numerical study has been performed to investigate the flow and heat transfer characteristics of fluid flow through heat exchanger tubes fitted with perforated conical rings. The holes are circular, and the number of holes N is ranged from 0 to 10. The influences of perforated conical ring diameter ratios D2/D1=0.4,0.5and0.6 and the hole diameter ratios d/D=0.06,0.1and0.14 on average Nusselt number, friction factor and thermal performance factor are reported. This analysis is performed in the turbulent flow regime 4000⩽Re⩽14,000 and the governing equations are solved by using (RNG) k-∊ model. Due to strong turbulent intensity, perforated conical rings lead to more flow perturbation and...