Loading...
Search for:
heating
0.011 seconds
Total 1781 records
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...
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...
Visualization and comparative investigations of pulsating ferro-fluid heat pipe
, Article Applied Thermal Engineering ; Volume 116 , 2017 , Pages 56-65 ; 13594311 (ISSN) ; Saidi, M. H ; Shafii, M. B ; Vandadi, M ; Kalan, K ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
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...
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...
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...
Enhancement of pool boiling heat transfer using ferromagnetic beads in a variable magnetic field
, Article Applied Thermal Engineering ; Volume 164 , 2020 ; Ebrahimi Dehshali, M ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The pool boiling is one of the heat transfer mechanisms used in cooling systems. Using an external force to improve the efficiency of thermo-fluid systems is among the most effective approaches, and also highly applicable in enhancing heat transfer. In this study, the pool boiling of water, as the working fluid, in the presence of a variable magnetic field, is studied. To this end, ferromagnetic beads were placed on the boiling surface, and the effect of their movements due to a variable magnetic field was observed and measured. The number of beads was selected such that they would cover 1/3, 1/2 and 2/3 of the surface in different cases and the magnetic field was controlled by altering...
Asymptotic and exact analysis for constructal optimization of microchannel heat sink
, Article 1st ASME Micro/Nanoscale Heat Transfer International Conference, MNHT08, Tainan, 6 January 2008 through 9 January 2008 ; Volume Parts A and B , 2008 , Pages 791-799 ; 0791842924 (ISBN); 9780791842928 (ISBN) ; Saidi, M. H ; Sharif University of Technology
2008
Abstract
Microchannels are at the fore front of today's cooling technologies. They are widely being considered for cooling of electronic devices and in micro heat exchanger systems due to their ease of manufacture. One issue which arises in the use of microchannels is related to the small length scale of the channel or channel cross-section. In this work, the maximum heat transfer and the optimum geometry for a given pressure loss have been calculated for forced convective heat transfer in microchannels of various cross-section having finite volume for laminar flow conditions. Solutions are presented for 10 different channel cross sections, namely parallel plate channel, circular duct, rectangular...
The effect of local thermal non-equilibrium on conduction in porous channels with a uniform heat source
, Article Transport in Porous Media ; Volume 69, Issue 2 , 2007 , Pages 281-288 ; 01693913 (ISSN) ; Noghrehabadi, A. R ; Rees, D. A. S ; Sharif University of Technology
2007
Abstract
We examine the effect of local thermal non-equilibrium on the steady state heat conduction in a porous layer in the presence of internal heat generation. A uniform source of heat is present in either the fluid or the solid phase. A two-temperature model is assumed and analytical solutions are presented for the resulting steady-state temperature profiles in a uniform porous slab. Attention is then focussed on deriving simple conditions which guarantee local thermal equilibrium. © Springer Science+Business Media, Inc. 2006
A parametric study on radiant floor heating system performance
, Article Renewable Energy ; Volume 31, Issue 10 , 2006 , Pages 1617-1626 ; 09601481 (ISSN) ; Farhanieh, B ; Sharif University of Technology
2006
Abstract
Efficient radiant heating systems are promising technologies for energy saving in commercial and building sectors together with improving occupant thermal comfort. However, the thermal performance of radiant systems in buildings has not been fully understood and accounted for in currently available building energy simulation software. In this paper, the effects of design parameters on performance of a typical radiant floor heating system have been studied using finite element method. A radiant heating system includes a number of pipes filled with hot water. Therefore, several design parameters such as pipe diameter, type (material), number, thickness and cover of system are affected on the...
Symbiosis opportunities between food and energy system: The potential of manure-based biogas as heating source for greenhouse production
, Article Journal of Industrial Ecology ; Volume 25, Issue 3 , 2021 , Pages 648-662 ; 10881980 (ISSN) ; Golzar, F ; Bowman, G ; Hellweg, S ; Roshandel, R ; Sharif University of Technology
John Wiley and Sons Inc
2021
Abstract
The concept of symbiosis, a mutually beneficial relationship, can be applied to food and energy systems. Greenhouse systems and biogas plants are interesting technologies for food–energy symbiosis, because both are usually based in rural areas and offer opportunities for the exchange of materials (e.g., biomass waste from the greenhouse as input to biogas plants) and energy (heat from biogas co-generation for heating greenhouses). In this paper, the focus lies on manure resources for biogas in Switzerland, because manure amounts are high and currently largely underused. We provide a spatial analysis of the availability of manure as feedstock to biogas plants and heat source for greenhouses....
Experimental investigation of the effect of copper electrodeposition on the aluminum surface and addition of ethylene glycol on boiling heat transfer coefficient
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; 2021 ; 09477411 (ISSN) ; Mahdi, M ; Abarghooei, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
In this research, the effect of surface characteristics on boiling heat transfer has been investigated experimentally. For this purpose, a device with the ability to automatically record the liquid temperature of the inlet and outlet of the test area, calculate the coefficient of boiling heat transfer, and heat flux has been developed. The automatic temperature stability of the working fluid and the ability to investigate the effect of surfaces with different characteristics (in terms of material and surface structure) on the boiling heat transfer parameters are the most important features of this device. The performance of the experimental setup was evaluated by the modified "Chen" equation...
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...
Experimental investigation of the effect of copper electrodeposition on the aluminum surface and addition of ethylene glycol on boiling heat transfer coefficient
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 58, Issue 5 , 2022 , Pages 801-812 ; 09477411 (ISSN) ; Mahdi, M ; Abarghooei, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
In this research, the effect of surface characteristics on boiling heat transfer has been investigated experimentally. For this purpose, a device with the ability to automatically record the liquid temperature of the inlet and outlet of the test area, calculate the coefficient of boiling heat transfer, and heat flux has been developed. The automatic temperature stability of the working fluid and the ability to investigate the effect of surfaces with different characteristics (in terms of material and surface structure) on the boiling heat transfer parameters are the most important features of this device. The performance of the experimental setup was evaluated by the modified "Chen" equation...
Thermal and hydraulic performance of rectangular microchannel heat sinks with trapezoidal porous configuration
, Article Numerical Heat Transfer; Part A: Applications ; Volume 81, Issue 3-6 , 2022 , Pages 72-93 ; 10407782 (ISSN) ; Vafai, K ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In this article, the thermal and hydraulic capacity of a rectangular microchannel heat sink with different trapezoidal porous configuration’s inlet heights (Formula presented.) and outlet heights (Formula presented.) are examined. A three-dimensional model is used for microchannels with miscellaneous trapezoidal porous configuration’s inlet and outlet heights, and the laminar fluid flow and conjugate heat transfer equations are numerically solved. Darcy-Brinkmen-Forchheimer equation is utilized for transport through the porous region. For microchannels with miscellaneous porous distribution’s inlet and outlet heights, the Nusselt number, pressure drop and figure of merit (FOM), a criterion...
Open-loop pulsating heat pipes charged with magnetic nanofluids: powerful candidates for future electronic coolers
, Article Nanoscale and Microscale Thermophysical Engineering ; Volume 18, Issue 1 , 2014 , Pages 18-38 ; ISSN: 15567265 ; Taslimifar, M ; Haghayegh, S ; Hannani, S. K ; Shafii, M. B ; Saidi, M. H ; Afshin, H ; Sharif University of Technology
Abstract
The present research proposes an effective method to enhance the heat transport capability of conventional electronic coolers and improve their thermal management. Pulsating heat pipes (PHPs) are outstanding heat transfer devices in the field of electronic cooling. In the present study, two sets of open-loop pulsating heat pipes (OLPHPs) for two different magnetic nanofluids (with and without surfactant) were fabricated and their thermal performance was experimentally investigated. Effects of working fluid (water and two types of magnetic nanofluids), heating power, charging ratio, nanofluid concentration, inclination angle, application of a magnetic field, and magnet location are described....
Twisted bundle heat exchangers performance evaluation by CFD (CJ12/5054)
, Article International Communications in Heat and Mass Transfer ; Volume 39, Issue 10 , 2012 , Pages 1654-1660 ; 07351933 (ISSN) ; Farhadi, F ; Sharif University of Technology
Abstract
Shell and tube heat exchanger with single twisted tube bundle in five different twist angles, are studied using computational fluid dynamics (CFD) and compared to the conventional shell and tube heat exchanger with single segmental baffles. Effect of shell-side nozzles configurations on heat exchanger performance is studied as well. Heat transfer rate and pressure drop are the main issues investigated in the paper. The results show that, for the same shell-side flow rate, the heat transfer coefficient of heat exchanger with twisted tube bundle is lower than that of the heat exchanger with segmental baffles while shell-side pressure drop of the former is even much lower than that of the...
Analysis of entropy generation and convective heat transfer of Al 2O 3 nanofluid flow in a tangential micro heat sink
, Article International Journal of Heat and Mass Transfer ; Volume 55, Issue 15-16 , July , 2012 , Pages 4366-4375 ; 00179310 (ISSN) ; Seyf, H. R ; Sharif University of Technology
2012
Abstract
Effect of using Al 2O 3-water nanofluids with different volume fractions and particle diameters on generated entropy, hydrodynamic performance and heat transfer characteristics of a tangential micro-heat sink (TMHS) was numerically investigated in this research. Results indicated that considerable heat transfer enhancement is possible when using Al 2O 3-water nanofluids as coolant and clearly the enhancement improves with increasing particles concentration and decreasing particles size. However, using nanofluid has also induced drastic effects on the pumping power that increases with particles volume fraction and Reynolds number. Finally, it was found that generated total entropy decreases...
Experimental investigation into laminar forced convective heat transfer of ferrofluids under constant and oscillating magnetic field with different magnetic field arrangements and oscillation modes
, Article Experimental Thermal and Fluid Science ; Volume 68 , November , 2015 , Pages 601-611 ; 08941777 (ISSN) ; Moazami Goudarzi, H ; Shafii, M. B ; Sharif University of Technology
Elsevier Inc
2015
Abstract
In this study, the effects of ferrofluids on the forced convective heat transfer in a tube with a round cross section under constant heat flux in the laminar flow regime are investigated experimentally. For this purpose, an experimental setup was designed and built. Furthermore, the effects of an external magnetic field on the forced convective heat transfer were examined for various Reynolds numbers and volume concentrations. The parameters of magnetic field strength, magnetic field arrangement, the constancy or oscillation of the magnetic field and also its oscillatory mode were examined. As a result of the experimental studies, in the absence of a magnetic field enhancement in convective...
Experimental study on heat transfer augmentation of graphene based ferrofluids in presence of magnetic field
, Article Applied Thermal Engineering ; Volume 114 , 2017 , Pages 415-427 ; 13594311 (ISSN) ; Mehrali, M ; Akhiani, A. R ; Tahan Latibari, S ; Dolatshahi Pirouz, A ; Metselaar, H. S. C ; Mehrali, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
The effect of a permanent magnetic field on the heat transfer characteristics of hybrid graphene-magnetite nanofluids (hybrid nanofluid) under forced laminar flow was experimentally investigated. For this purpose, a reduced graphene oxide-Fe3O4 was synthesized by using two-dimensional (2D) graphene oxide, iron salts and tannic acid as the reductant and stabilizer. Graphene sheets acted as the supporting materials to enhance the stability and thermal properties of magnetite nanoparticles. The thermo-physical and magnetic properties of this hybrid nanofluid have been widely characterized and it shows that the thermal conductivity increased up to 11%. The hybrid nanofluid behaves as a Newtonian...
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) ; Behshad Shafii, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
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...