Sharif Digital Repository

Heat pipe is a heat transfer device that may have a thermal conductance hundreds of times higher than that of copper. Currently, heat pipes have been used in numerous applications including satellite thermal management, energy systems for energy recovery and energy conversion, and electronics cooling, particularly in laptop and desktop computers. In this thesis, a new application of the heat pipe in an automotive engine is introduced. In this application, heat pipes are incorporated into the radiator of the automotive engine for more efficient heat transfer. In particular, the employment of the heat pipes would allow the gravity to be used as the driving force for the liquid... 

Since oil prices continue to increase, energy conservation remains the prime industrial concern. Existing processes in power plants and oil refineries are not energy efficient as they should be therefore new projects can be defined to increase the energy efficiency without incurring any cost. The most appropriate utility for the processes should be explored to reduce emissions, increase the plant capacities and improve product qualities and energy efficiencies by one coherent strategic plan for the overall site which can be achieved by a full understanding of pinch technology and awareness of the available tools for applying it in practical way. Since the distillation unit of crude oil... 

Solar distillation is a comparatively easy treatment of brackish (i.e. contain dissolved salts) water supplies. Distillation is a well-known process, which may be used for water filtration utilizing heating sources. In this research, the solar distillation set with heat-pipes was made and tested in 18 months.At the first step, during four days, the pipes were filled with some water to certain height every day while temperature and produced water were estimated. At the second step, the vacuum pipes were filled with some oil and tested for 4 different heights within 4 days; and in final steps, aluminum chips, washing wire and metal foam were shaded into the tank then tested by an optimum water... 

In this paper, a one-dimensional and two-dimensional numerical approach is used to study the effect of various parameters such as micro combustor height, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system (A-D-R) that leads to two stiff systems of PDEs, which can not be solved by conventional Computational Fluid Dynamics (CFD) methods. In the present work, Strang splitting method, which is suitable for nonlinear stiff... 

Micro combined heat and power (MCHP) system is one of the most worldwide considered energy saving with high total efficiency systems. This research presents the application of MCHP to small scale users such as residential or light commercial buildings. Initially, the available technology in micro scale that can be used as an energy generator has been specified and categorized. Since then, by using the overall energy purchased cost by households assuming the energy carriers are kerosene, gas and electricity, total demand has been determined considering that the electricity expenses showing the use of electric appliances and the gas expenses expressing the cost of domestic hot water and... 

Contactless and nonintrusive methods in particulate manipulation have been considered by many investigations. Particularly the use of these methods in characterization of micro and nano flows is in the focus of interests. Laser usage in the particulate systems has been dramatically increased during the last two decades. Laser can be used either as an illustration or excitation source in these systems. So-called optical tweezers use the laser beam for particle manipulation and characterization based on the hydrodynamic interaction of the laser beam with particles. There are numerous works being conducted in the field of particulate manipulation and characterization using laser beam.Present... 

Modern microelectronic systems generate a large amount of heat which must be transferred out of the system without excessive temperature rise. Conventional forced air convection and microchannel cooling plates have reached their performance limits Nanofiuids are proposed as an innovative way to solve the problem. A nanofiuid is nanoscale solid particles dispersed in a traditional heat transfer liquid. Some studies show an anomalous increase in the thermal conductivity for stationary nanofiuids. However, there are only few previous studies on the convection heat transfer rate and viscosity of nanofiuids. Both convection and stationary measurements of the thermal conductivity are widely... 

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... 

In petrochemical, Process condensate is mixtures of dissolved gasses and water. Process condensate striper tower is a physical separation equipment where dissolved gasses remove from water by saturated steam. The Process condensate feed is introduced at the top of the column and the steam input is located at the bottom. When the process condensate enters the stripper tower, it comes down the tower also when the steam enters the tower, it goes up, because there is packing portion in the stripper tower and two streams are countercurrent, as result contact between steam and process condensate, a lot of dissolved gases vapors and exits with steam from top of tower. After leaving the tower, the... 

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.... 

There is a need for renewable energy sources to be more feasible. The purpose of this project is to develop a compact device that is able to harvest wind energy and transform it into electrical energy using the concept of vortex shedding. When calibrated correctly, the vortex shedding will induce resonant oscillation. Electricity would be collected from this oscillation using a magnet and coil assembly. This method was proven to work in water, but has not been applied to air currents. Our group designed and built a small-scale prototype to be tested in closed circuit wind tunnel. The wind harvester works at a moderate wind range of 3 to 5 m/s. Data was collected on the amplitude and... 

One of the biggest problems in improving the performance of submersible propellers is the acoustic standard in conventional propellers. Recently, new solutions in propellers geometry have been used to reduce non-cavitation noise. Designing CRP licenses is one of these methods. This research includes numerical analysis. Numerical analysis in this research solves RANS equations of flow and extraction of hydrodynamic parameters and impeller noise in Ansys software. The results of numerical hydrodynamic solution are validated by laboratory results.DTMB 4119 three-blade propeller is used for hydrodynamic and hydroacoustic validation. The solution of Lighthill equations by FW-H method is... 

EOR (oil enhanced recovery) is very important as oil is a nonrenewable resource. Depending on the characteristics of the rock formation, primary production can result in the recovery of up to 20% of the oil originally in the rock. This means that at least 80% of the oil may remain in the rock unless additional technology is used to increase the recovery. Before finding best way to do for EOR, scientists must study properties of different porous media that oil is trapped between its grains. Most of research and studies investigate networks of porous media but this work focused on oil movement through a pore space in porous media lonely not in network by waterflooding. Studying a pore space is... 

Heat pipes are useful devices in heat transfer, renewable energies and cooling systems in particular. According to various application of this systems in different industries, performance improvement of this devices has gained much importance. Working fluid is one of the effective factors on pulsating heat pipes. Since heat transfer in PHPs is natural convection and two-phase, specific heat and thermal conductivity of working fluid have an important role in the performance of pulsating heat pipes. In the present study, the effect of using nano-encapsulated PCM along with reduced graphene oxid (RGO) dispersed in water and their mixture as working fluid has on the performance of PHPs has been... 

Liquid marbles are droplets enwrapped by a layer of micro/nanoparticles. Due to the insulation of inner fluid from the environment, the lower evaporation rate of the fluid, and the capability of motion even on hydrophilic surfaces, these liquid marbles, as an alternative to conventional droplets, have attracted the attention of researchers in digital microfluidics. Utilizing ferrofluid as the liquid core of the liquid marbles enables remote control over the liquid marbles by an external magnetic field. In this research, the dynamic behavior of ferrofluid liquid marbles under the magnetic field generated by an electromagnet is investigated. In this research, governing physics on the motion of... 

In this Study, experimental tests were carried out to investigate the effects of adding water-based ferrofluid to diesel fuel in a diesel engine. These effects included the combustion performance and exhaust emission characteristics of the diesel engine. To this end, emulsified diesel fuels of 0, 0.4, and 0.8 ferrofluid/Diesel ratios by volume were used in a four stroke diesel engine. The results indicate that adding ferrofluid to diesel fuel has a perceptible effect on engine performance, increasing the brake thermal efficiency and decreasing the brake specific fuel consumption as compared to diesel fuel. Furthermore, adding ferrofluid to diesel fuel increased the exhaust gaseous... 

Increasing fossil fuel consumption has led to serious problems in energy supply and environmental issues such as global warming, air pollution, ozone depletion, and security issues. A strategy to improve energy consumption requires recycling wasted energy and preventing it from being released into the environment. A wide range of available heat sources such as heat dissipation in the transportation industry, solar heat, biomass and geothermal have low-temperature, which contain large amounts of energy but they do not have enough temperature to make them economically viable and cost-effective. Several applied technologies have been proposed to utilize these resources, among which the organic... 

Over the last few years, exploiting particle sensing systems for micro-nanoparticles has grabbed much attention. Attaining the physical properties of particles using resistive pulse sensing has been one of the utmost applicable methods of sensing particles. Pores are pivotal elements of systems based on resistive pulse sensing. Two electrodes are placed at both sides of the pore, filling the containers with an electrolyte solution. Pulses of particle translocation across the pore can be recorded by applying a voltage across the electrodes. In more developed versions of resistive pulse sensing systems, pore size is tunable to attain polydisperse particles within a dispersion. In subsequent... 

Improving efficiency of heat exchangers has always been an important concern for the industry. Pulsating Heat Pipes (PHPs) are novel and efficient technology in the field of heat transfer. PHPs are widely used in solar water heaters, solar desalination systems, etc. In this research, thermal performance of Open Loop Pulsating Heat Pipes (OLPHPs) using three different ferrofluids (ferrofluid without surfactant and nanoparticles’ coating, ferrofluid with coating of nanoparticles, and ferrofluid with surfactant) is experimentally investigated. In addition, effects of charging ratio (20, 40, 60, and 80%), heating power (20, 30, 40, 50, 60, 70, 80, 100, 120, 140, 160, 180, 200, 240, 280, 320,... 

In this study, a mixture of nano-encapsulated phase change materials in water has been used as a working fluid in a pulsating heat pipe in order to investigate its thermal performance. The results of the experiments showed that using the nano-encapsulated paraffin dispersed in water as working fluid improves heat transfer and decreases the thermal resistance of the pulsating heat pipe. On the other hand, there is an optimal concentration among tested concentrations for nano-encapsulated paraffin, in which increasing its concentration due to the increased dynamic viscosity of the fluid causes an increase in the thermal resistance of the pulsating heat pipe. Enhancement in the thermal...