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heat-transfer
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Experimental examination of utilizing novel radially grooved surfaces in the evaporator of a thermosyphon heat pipe
, Article Applied Thermal Engineering ; Volume 169 , 2020 ; Faegh, M ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
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 enhancement of a fin-and-tube compact heat exchanger by employing magnetite ferrofluid flow and an external magnetic field
, Article Applied Thermal Engineering ; Volume 164 , 2020 ; Rostamzadeh, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Compact heat exchangers as modern industrial devices are designed to improve heat recovery and saving energy processes in restricted spaces. In the current study, effect of a uniform external magnetic field with Fe3O4/water nanofluid for heat transfer enhancement of a fin-and-tube compact heat exchanger is numerically investigated. The obtained results are verified by the available experimental data to demonstrate accuracy of the present simulation. The results indicated that the local and average heat transfer coefficients increase around the tubes in the presence of an external magnetic field due to the vortex formation behind the tubes as well as the flow pattern alteration in the heat...
A review on the applications of micro-/nano-encapsulated phase change material slurry in heat transfer and thermal storage systems
, Article Journal of Thermal Analysis and Calorimetry ; 2020 ; Mahmoudian, A ; Mohammadi, O ; Shafii, M. B ; Jafari Mosleh, H ; Zandieh, M ; Ahmadi, M. H ; Sharif University of Technology
Springer Netherlands
2020
Abstract
In modern heat transfer systems, thermal storage not only causes the balance between demand and supply, but also improves the heat transfer efficiency in these systems. In the present study, a comprehensive review of the applications of micro- or nano-encapsulated phase change slurries (MPCMs/NPCMs), as well as their effects on thermal storage and heat transfer enhancement, has been conducted. MPCMs/NPCMs have a myriad of applications and various usages such as pipe and channel flows, photovoltaic/thermal, solar heaters, air conditioning systems, storage tanks and heat pipes that have been categorized and studied. It was found that there are many advantageous adding MPCM/NPCM to the base...
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...
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,...
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
Heat transfer of swirling impinging jets ejected from Nozzles with twisted tapes utilizing CFD technique
, Article Case Studies in Thermal Engineering ; Volume 6 , September , 2015 , Pages 104-115 ; 2214157X (ISSN) ; Mokhtari, M ; Haghshenasfard, M ; Barzegar Gerdroodbary, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
This research investigated the forced convection heat transfer by using the swirling impinging jets. This study focused on nozzles, which equipped with twisted tapes via a numerical approach. The computational domain created by utilizing the fully structured meshes, which had very high quality from the viewpoint of aspect ratio and skewness. The numerical simulations were performed at four different jet-to-plate distances (L/D) of 2, 4, 6 and 8, four Reynolds numbers of 4000, 8000, 12,000 and 16,000, and also four different twist ratios (y/w) of 3, 4, 5 and 6. The mesh-independent tests were conducted based upon the average Nusselt number. The obtained results revealed good agreement with...
Numerical investigation of the performance of a U-shaped pulsating heat pipe
, Article Heat Transfer Engineering ; Volume 31, Issue 14 , Oct , 2010 , Pages 1155-1164 ; 01457632 (ISSN) ; Rasoulian, R ; Shafii, M. B ; Saboohi, Y ; Sharif University of Technology
2010
Abstract
In this research the performance of a U-shaped pulsating heat pipe (PHP) was investigated using numerical methods. This heat pipe consists of two sections: The evaporator is set at the two ends of the pipe, and the middle part of the pipe comprises the condenser section. This heat pipe is a type of open looped pulsating heat pipe. The governing equations are derived analytically from the continuity, momentum, and energy equations and are solved implicitly. In this model, considering the liquid mesh, the rate of convection and boiling heat transfer in the U-shaped PHP, which has not been investigated as of yet, are examined. The effect of the evaporator temperature on the pulse amplitude and...
A coupled adjoint formulation for non-cooled and internally cooled turbine blade optimization
, Article Applied Thermal Engineering ; Volume 105 , 2016 , Pages 327-335 ; 13594311 (ISSN) ; Mazaheri, K ; Chaharlang Kiani, K ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Most researches on the application of the adjoint method in turbine blade design are concentrated on the aerodynamic shape optimization without considering the heat transfer to/from the blade material. In this study, the adjoint method is extended to the conjugate heat transfer problems in which the viscous flow field is coupled to heat transfer in the solid region. Introducing a new adjoint variable in the solid domain, a heat adjoint equation is derived which is coupled with the energy adjoint equation in the fluid zone at the fluid/solid interface. The detailed mathematical description associated with the derivation of the heat adjoint equation with corresponding boundary conditions are...
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 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 PV cooling by using single turn pulsating heat pipe
, Article International Journal of Heat and Mass Transfer ; Volume 127 , 2018 , Pages 203-208 ; 00179310 (ISSN) ; Ghasempour, R ; Shafii, M. B ; Ahmadi, M. H ; Yan, W. M ; Nazari, M. A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Electrical efficiency of photovoltaic (PV) modules depends on their working temperature. Effective cooling is required in order to achieve higher performance. Pulsating heat pipes (PHPs) are compact heat transfer devices with high effective thermal performance due to the two-phase heat transfer mechanism. Since the lower temperature of PV modules leads to higher electricity generation and better efficiency, PHPs can be applied for PV cooling. In this work, the PV cooling by applying a single turn PHP is numerically investigated. In addition, a copper fin with the same dimensions as the PHP for cooling the PV panel is simulated to compare the performance of the PHP with a solid metal like...
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...
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...
Heat transfer characteristics of high flow rate electrospray and droplet cooling
, Article Applied Thermal Engineering ; Volume 162 , 2019 ; 13594311 (ISSN) ; Jafari, M ; Morad, M. R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Electrospray cooling is experimentally examined for high volumetric flow rates (80 mL/h) stabilized by a novel hemispherical nozzle. Stability of the Taylor cone-jet mode of this nozzle is increased by interaction of the discharging liquid with the outer wall of a hemispherical cap, installed at the tip of a simple nozzle. The liquid can then be discharged at high flow rates at the same mode. The liquid is ethanol and the test surface temperature as well as the cooling heat flux are measured. The results of the surface temperature, the heat flux and the heat transfer coefficient are compared between the three cases. The first and main case is the electrospray using the novel hemispherical...
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) ; Ahmadi, M. H ; Sadeghzadeh, M ; Shafii, M. B ; Goodarzi, M ; Sharif University of Technology
Central South University of Technology
2019
Abstract
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...
Numerical investigation of rectangular-cut twisted tape insert on performance improvement of heat exchangers
, Article International Journal of Thermal Sciences ; Volume 138 , 2019 , Pages 75-83 ; 12900729 (ISSN) ; Esfahani, J. A ; Sharif University of Technology
Elsevier Masson SAS
2019
Abstract
A numerical analysis has been performed to investigate the flow structure and thermal hydraulic performance of turbulent flow through circular tube equipped with twisted tapes with different cut shapes. The geometries of cuts are rectangular with different cut ratios 0.25
Entropy analysis and thermal optimization of nanofluid impinging jet using artificial neural network and genetic algorithm
, Article International Communications in Heat and Mass Transfer ; Volume 119 , December , 2020 ; Eghtesad, A ; Jamali, S ; Afshin, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Optimized and informed design of impinging jets can effectively enhance their rate of heat transfer. One practical pathway for such designing is to add nanoparticles to a background fluid. Here, we determine the effects of nanoparticle chemistry, their size, and their total volume fraction in water on the rate of heat transfer. We perform a comprehensive optimization using artificial neural network (ANN) and genetic algorithm (GA) to systematically study the enhanced heat transfer in nanofluids compared to pure water in obtaining a uniform cooling on a constantly heated surface in a turbulent flow. Our results indicate that increasing the size and concentration of nanoparticles enhances the...
The effect of variable temperature and location on relative thermal conductivity (RTC) on the heat pipe in the presence of AL2O3 nanoparticles: Numerical and optimization approaches
, Article Journal of the Taiwan Institute of Chemical Engineers ; Volume 124 , 2021 , Pages 132-149 ; 18761070 (ISSN) ; Mohammadiun, H ; Alizadeh, R ; Mesgarpour, M ; Younesian, A ; Jowkar, S ; Sharif University of Technology
Taiwan Institute of Chemical Engineers
2021
Abstract
Background: The cooling system is one of the important parts of new devices such as smartphones, servers, and other electrical devices. By employing the almost all heat transfer methods such as conduction, evaporation and condensation, heat pipes are the best choice to increase the heat transfer. The thermal conductivity of heat pipe is much higher than fins because they benefit from condensation and evaporation simultaneously. Methods: This study tries to present relative thermal conductivity base on temperature and length of a heat pipe in optimized geometry. To achieve this aim, unsteady, multiphase fluid was considered inside the heat pipe. Evaporation, condensation, and conduction were...
Characteristics of heat and mass transfer in vapor absorption of falling film flow on a horizontal tube
, Article International Communications in Heat and Mass Transfer ; Volume 32, Issue 9 , 2005 , Pages 1253-1265 ; 07351933 (ISSN) ; Farhanieh, B ; Sharif University of Technology
2005
Abstract
The absorber is an important component in absorption machines and its characteristics have significant effects on the overall efficiency of absorption machines. This article reports on the results of numerical studies on the characteristics of falling film LiBr-H2O solution on a completely wetted horizontal tube and the associated vapor absorption in the Reynolds number range of 5 < Re < 100. The boundary layer assumptions are used for the transport of mass, momentum and energy equations and the finite difference method is employed to solve the governing equations in the film flow. The heat and mass transfer coefficients are expressed in the forms of Reynolds number, Prandtl number and...