Sharif Digital Repository

Fuel cell-based CHP systems for distributed residential power generation represent an interesting alternative to traditional thermoelectric plants. This is mainly due to the high efficiency obtainable in the production of electricity and heat in a decentralized, quiet and environmental friendly way. The current thesis focuses on the development, in Matlab_Simulink environment, of a complete dynamic model of a residential cogenerative (CHP) energy system consisting of the Proton Exchange Membrane fuel cell (PEMFC), in two scenarios. The first scenario emphasizes on use of fan and usual Heat Exchanger for cooling of Proton membrane fuel cell and conveying generated heat in PEM fuel cell to... 

Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. Most of desalination methods require consuming large amounts of fossil fuels. Solar distillation is one of the best techniques from another available techniques for desalinating in small-scale brackish water. The main problem of these systems is the low rate of water production.Single basin solar still is a very simple solar device used for converting available brackish or waste water into potable water. This device can be fabricated easily with locally available materials. The maintenance is also cheap and no skilled labor is required. It can be a suitable solution to solve drinking water problem.... 

Pulsating heat pipe (PHP) is a two-phase device for the means of transferring high heat fluxes and is used extensively for the electronic cooling. In this study the different flow regimes in PHP with different fluids have been investigated. In this research, 3 different fluids including: Pure fluids, Ferro-fluid and surfactant solution with %50 filling ratio have been used. For ferro-fluid, 5 different concentrations and 3 type of magnetic fields have been operated in 2 different heat pipes. Results show that ferrofluid is more stable in Pyrex made-heat pipe for long period of time and no magnet mode has the best thermal performance due to high conductivity of fluid. In copper made-heat pipe... 

The impact of droplets is a widely used method for creating direct heat transfer between two fluids. This method enhances heat transfer between the working fluid and the phase change material (PCM). Therefore, a thorough investigation has been carried out on the impact of an acetone droplet on the surface of a pool of molten paraffin, which leads to the simultaneous boiling of the acetone droplet and solidifying part of the paraffin in contact with the acetone. The dynamics of impact, the depth and width of the crater, the jet, and the crown formed as a result of the impact have been reported with varying Weber numbers (ranging from 74 to 375), and the temperature of the pool surface of the... 

The main purpose of this thesis is to analyze the total productive maintenance based on computerized maintenance management system. At first, a detailed study on total productive maintenance is performed and then the requirements of this maintenance strategy are specified. Also, a computerized maintenance management system is defined which can help total productive maintenance to reach to its requirements. Finally, a conceptual model and entity-relationship model for computerized maintenance management system data base has been created  

Today microbubbles are broadly used as ultrasound contrast agents. These bubbles enhance the image resolution of B-mode pictures. Flow focusing in microchannels could provide us the goal of one-size bubbles generation. Microbubbles could use as tracers in Echo_PIV method to determine the velocity profile in main body vessels such as carotid. In this paper we introduce a new production method to fabricate a low-cost microchannel for preparing Microbubble contrast agents (less than 50 microns) by using some surface active agents and a viscosity enhancing material to obtain appropriate Microbubbles with desired life time and stability for any in vitro infusion for velocity measurement. By... 

Experiments were performed to explore the free convective hat transfer characteristics of water based nanofluids. Experiments of natural convection over a vertical flat plate with constant heat flux in water-based nanofluids with Ag and TiO2 nanoparticles were performed. Velocity boundary layer measured using PIV method. Also convective heat transfer coefficient obtained using three thermometers behind the wall. Various test cases with different heat fluxes on the wall are considered. Two volumetric concentrations of Ag nanofluid, 1% and 2%, and TiO2 nanofluid, 1% and 2%, were tested in the present study. It was shown that, with increasing nanofluid concentration, velocity boundary layer... 

On track to achieve heat transfer methods for small-scale, this research describes the design process of fabrication and experimental analysis of micro heat pipes with a rectangular section. First, the overview of micro-fluid systems and conventional mechanisms of heat transfer in these systems is discussed. Then, in order to describe the research theory and principles of heat pipe, various types of heat pipes micro scale and macro scaled are analyzed. After that, the method used for fabrication of a micro heat pipe without grooves is described. A new method for fabrication of MHP is investigated in this study. By using this method, one fiber glass board is fabricated by printed circuit... 

Symmetric T junctions have been used widely in microfluidics to generate equal-sized microdroplets, which are applicable in drug delivery systems. A newly proposed method for generating unequal-size microdroplets at a T junction is investigated theoretically and experimentally. Asymmetric T junctions with branches of identical lengths and different cross-sections are utilized for this aim. A novel equation for the critical breakup of droplets at asymmetric T junctions and one for determining the breakup point of droplets are developed. A good agreement was observed between the theories (novel and previous) and the experiments  

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... 

Considering the advantages and disadvantages of reported micropumps, we aimed to introduce a novel idea to diminish the disadvantages and promote the advantages of PiezoElectric micropumps. This novel idea operates based on a mercury slug actuation in a microchannel. This cyclic motion of the mercury slug which is similar to a piston, push the fluid in the microchannel and pump the flow. However, to bring this idea into the practice, a control system must be designed. This system contains: LABVIEW code, DAQ board & a switching Board. The pattern of actuating mercury is drawn in LABVIEW. DAQ Board produces electrical signals according to LABVIEW code. Switching board will transform the... 

Developing of electric instruments with high performance needs high capacity heat transfer equipments. Pulsating heat pipes have better performance compared with normal heat pipes and can be used for cooling electronic instruments in near future. Also, one specific kind of heat pipes, which is called rotating pulsating heat pipe, can be used in cooling the turbine blades. Rotating pulsating heat pipe is a mechanism in which the pipes can rotate around the axis perpendicular to the plane of pipes. In this research one rotating heat pipe was built and the effects of heat input, filling ratio and rotational acceleration were examined experimentally. The Innovation in the research was to obtain... 

In this investigation Magneto Mercury Reciprocating Micrpump (MMRM) the combination of Magneto-Hydrodynamic and Reciprocating micropumps has been analyzed. To achieve the analytical and numerical solution of one-tank and three-tank MMRM, the momentum, continuity, volume fraction and magnetohydrodynamic equations have been presented. The dimensionless analytical solution of one-phase and two-phase three dimensional MHD flow in the condition of using constant current and potential electrical source, has been offered.
The boundary between mercury and air has been tracked via VOF method in OpenFOAM software. VOF equation has been solved by explicit method with variable time step and maximum... 

Nowadays, as a result of population growth and groundwater resources pollution, many countries in the world are facing serious water crises. Several alternative solutions have been investigated to overcome this obstacle. Atmospheric water vapor processing (AWVP) is a new solution to generate freshwater from ambient moist air. The atmosphere surrounding the earth is potentially a valuable water resource which contains a large amount of freshwater. This paper addresses the effectiveness of thermoelectric coolers (TECs) for refrigeration to produce freshwater from ambient air. Consequently, both numerical and experimental analysis are then used as the basis of water production calculation. 18... 

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... 

This research aims to design and build a device that Using solar energy and can be used as water heaters and water desalination and water from the soluble hygroscopic. For this purpose, a combination of evacuated tube collector with parabolic through collector with sun tracking mechanism is used. sun tracking mechanism is polar and works with optical sensor. in this research we have designed new setup with evacuated tube collector for direct desalination and water heater. in this method heat pipes have been omitted from setup that cause high performance in heat transfer from evacuated tube collector to water and is minimized losses. 15w air compressor used to increased rate of evaporation ... 

A Loop heat pipe (LHP) is an efficient two phase heat transfer device that is widely used in cooling applications. In this research a novel LHP was designed, fabricated and its performance was investigated through various experiments. The novel LHP has a new arrangement in evaporator and reservoir configuration in comparison with conventional LHPs, which results in a different energy and fluid flow. In addition, the novel LHP has a new mechanism for active control of working temperature which was not already used. Aside from its good performance, this LHP has easier and lower cost manufacturing process compared with the conventional ones. Also the proposed temperature control method is... 

Oil pump is a prominent part which has been described as a vehicle heart. Any malfunction or improper design may lead to engine failure. beside engine, proper design of oil route and lubrication system of vehicle, are main factor in engine design, which provide higher efficiency with lower pressure drop. lubrication system should be able to provide required pressure and flow of oil in vast range of engine rotation speed. also minimum energy waste in higher rpm is a key factor which happens due to reverse flow from output to input of pump in the relief valve. The aim of this thesis focus on design of oil pump and lubrication system of 4 cylinder 16 valve of 1600 cc inline engine. which is...