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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

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. Source

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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