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Khalili M.,Sharif University of Technology | Khalili M.,Sharif Energy Research Institute SERI | Shaii M.B.,Sharif University of Technology
Scientia Iranica | Year: 2016

Heat pipes are important cooling devices that are widely used to transfer high heat loads with low temperature differences. In this paper, thermal performance of a novel type of sintered-wick heat pipe, namely, partly sintered-wick heat pipe, was investigated. The heat pipe was filled with degassed water and acetone, as working uids, and effects of filling ratio, orientation, and heat inputs were tested. Moreover, conditions at which dryout occurred were presented. The results showed that the best filling ratio for both working uids is about 20%. The heat pipe filled with water has better thermal performance than that filled with acetone; thus, the thermal resistances of the 20% water-filled heat pipe are approximately 7%, 27%, and 75% lower than those of the 20% acetone-filled one in the vertical, horizontal, and reverse-vertical modes, respectively. This novel type of sinteredwick heat pipe has good thermal performance in the horizontal mode and can be used in no-gravity conditions, i.e. space applications. © 2016 Sharif University of Technology. All rights reserved.


Kargar Sharif Abad H.,Islamic Azad University at Tehran | Ghiasi M.,Sharif Energy Research Institute SERI | Jahangiri Mamouri S.,Sharif University of Technology | Shafii M.B.,Sharif University of Technology
Desalination | Year: 2013

The application of the solar energy in thermal desalination devices is one of the most beneficial applications of the renewable energies. In this study, a novel solar desalination system is introduced, which is benefited from the undeniable advantages of pulsating heat pipe (PHP) as a fast responding, flexible and high performance thermal conducting device. Results show a remarkable increase in the rate of desalinated water production and the maximum production reaches up to 875mL/(m2.h). However, the optimum water depth in basin and the filling ratio of the PHP are measured 1cm and 40%, respectively. © 2012 Elsevier B.V.


Ghofrani A.,Sharif University of Technology | Ghofrani A.,Sharif Energy Research Institute SERI | Dibaei M.H.,Islamic Azad University at Shahrood | Hakim Sima A.,Sharif Energy Research Institute SERI | Shafii M.B.,Sharif University of Technology
Experimental Thermal and Fluid Science | Year: 2013

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 and under different frequencies of the applied magnetic field in detail. The convective heat transfer coefficient for distilled water and ferrofluid was measured and compared under various conditions. The results showed that applying an alternating magnetic field can enhance the convective heat transfer rate. The effects of magnetic field, volume concentration and Reynolds number on the convective heat transfer coefficient were widely investigated, and the Optimum conditions were obtained. Increasing the alternating magnetic field frequency and the volume fraction led to better heat transfer enhancement. The effect of the magnetic field in low Reynolds numbers was higher, and a maximum of 27.6% enhancement in the convection heat transfer was observed. © 2013 Elsevier Inc.


Jahangiri Mamouri S.,Sharif University of Technology | Gholami Derami H.,Sharif University of Technology | Ghiasi M.,Sharif Energy Research Institute SERI | Shafii M.B.,Sharif University of Technology | Shiee Z.,Sharif University of Technology
Energy | Year: 2014

A desalination system consumes energy for production of freshwater. Since the solar energy is a low-cost, environmentally clean, and available energy throughout the world, it could be the best source of energy for such systems. In this work, a modified desalination system is presented which uses advantages of thermosyphon heat pipes as a fast and high performance thermal conducting device, and at the same time, employs the advantages of evacuated tube collectors (ETCs) which are flexible and have high performance in adverse weather conditions. Results show considerable increase in the production rate of desalinated water and system efficiency with a maximum production rate of 1.02 kg/(m2 h) and maximum efficiency of 22.9%. Furthermore, the optimum water depth in the basin is measured to be 2 cm, which is the same as the length of the heat-pipe's condenser section in the basin. © 2014 Elsevier Ltd. All rights reserved.


Salari A.,Sharif University of Technology | Hakimsima A.,Sharif Energy Research Institute SERI | Shafii M.B.,Sharif University of Technology
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2015

Lorentz force is the pumping basis of many electromagnetic micropumps used in lab-on-a-chip. In this paper a novel reciprocating single-chamber micropump is proposed, in which the actuation technique is based on Lorentz force acting on an array of microwires attached on a membrane surface. An alternating current is applied through the microwires in the presence of a magnetic field. The resultant force causes the membrane to oscillate and pushes the fluid to flow through microchannel using a ball-valve. The pump chamber (3 mm depth) was fabricated on a Polymethylmethacrylate (PMMA) substrate using laser engraving technique. The chamber was covered by a 60 μm thick hyper-elastic latex rubber diaphragm. Two miniature permanent magnets capable of providing magnetic field of 0.09 T at the center of the diaphragm were mounted on each side of the chamber. Square wave electric current with low-frequencies was generated using a function generator. Cylindrical copper microwires (250 μ4m diameter and 5 mm length) were attached side-by-side on top surface of the diaphragm. Thin loosely attached wires were used as connectors to energize the electrodes. Due to large displacement length of the diaphragm (∼3 mm) a high efficiency (∼90%) ball valve (2 mm diameter stainless steel ball in a tapered tubing structure) was used in the pump outlet. The micropump exhibits a flow rate as high as 490μl/s and pressure up to 1.5 kPa showing that the pump is categorized among high-flow-rate mechanical micropumps. © 2015 SPIE.


Yarahmadi M.,Sharif University of Technology | Yarahmadi M.,Sharif Energy Research Institute SERI | Moazami Goudarzi H.,Sharif University of Technology | Moazami Goudarzi H.,Sharif Energy Research Institute SERI | Shafii M.B.,Sharif University of Technology
Experimental Thermal and Fluid Science | Year: 2015

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 heat transfer was observed after using the ferrofluid compared with distilled water. In addition, convective heat transfer through the circular tube increased after using an oscillatory magnetic field. However, the heat transfer decreased after a constant magnetic field was applied. Based on the results obtained, the effects of the magnetic field are more intensified in the ferrofluids with higher volume concentration and flows with lower Reynolds number. Moreover, the effect of the oscillation frequency on the local heat transfer coefficient varies in different oscillatory modes of the magnetic field. The maximum enhancement of 19.8% was obtained in the local convective heat transfer by using the oscillating magnetic field compared with the case no magnetic field was applied. © 2015 Elsevier Inc.


Ebrahimi M.,Sharif University of Technology | Ebrahimi M.,Sharif Energy Research Institute SERI | Shafii M.B.,Sharif University of Technology | Bijarchi M.A.,Sharif University of Technology
Applied Thermal Engineering | Year: 2015

Abstract A desired circulatory flow in flat-plate closed-loop pulsating heat pipes (FP-CLPHPs), which may ameliorate electronic thermal management, was achieved by using the new idea of interconnecting channels (ICs) to decrease flow resistance in one direction and increase the total heat transfer of fluid. In order to experimentally investigate the effects of the IC, two aluminum flat-plate thermal spreaders - one with ICs (IC-FP-CLPHP) and one without them - were fabricated. The FP-CLPHPs were charged with ethanol as working fluid with filling ratios of 35%, 50%, 65%, and 80% by volume. Performance of interconnecting channels in different heat inputs was explored, and the results demonstrated the higher performance of pulsating heat pipes with ICs in comparison with heat pipes without them in a wide range of heat inputs and filling ratios. It has been observed that the most efficient performance of IC-FP-CLPHP occurred at the filling ratio of 65%. Flow visualization indicated that interconnecting channels affect the flow regime and enhance flow circulation and heat transfer in CLPHPs. In furtherance of investigating the viability of the idea, a numerical procedure has been followed on a single-phase liquid to show the role of interconnecting channels in achieving one-way flow. © 2015 Elsevier Ltd.


Khalili M.,Sharif University of Technology | Khalili M.,Sharif Energy Research Institute SERI | Shafii M.B.,Sharif University of Technology
Applied Thermal Engineering | Year: 2016

Thermal performance of a novel sintered wick heat pipe was investigated in this study. Two types of sintered wick heat pipes were fabricated and tested at different filling ratios of water, and their thermal resistances in different modes were compared. In the first type, wick was sintered annularly (conventional type), and in the other one (novel type of sintered wick) it was sintered only in one third of cross-section. Results showed that dry-out occurs at higher heat input by an increase in the filling ratio. Moreover, the best filling ratio is 20% for both heat pipes. Thermal resistances of the partly sintered wick heat pipe are approximately 28%, 17% and 47% lower than those of the annularly sintered one at 20% filling ratio in the vertical, horizontal and reverse-vertical modes, respectively. Gravity has a slight effect on partly sintered wick heat pipe performance in the horizontal mode. This novel type of sintered wick heat pipe has simpler structure, and its manufacturing is more affordable compared with the annularly sintered wick. Hence, the use of this type of novel heat pipe (partly sintered wick) rather than the conventional type (annularly sintered one) is recommended in most applications, especially in space conditions where the gravity is negligible. In addition, experimental results were compared with numerical ones, and it was shown that the Florez orthorhombic and Alexander models can provide reasonable predictions for the effective thermal conductivity of water-saturated sintered powder-metal wicks. © 2015 Published by Elsevier Ltd.

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