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... 

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... 

On-board hydrogen storage systems (as a substitute for fossil fuels) employing high-pressure metal hydrides, promise advantages including high volumetric capacities and cold start capability. In this project, we discuss the development of a system simulation model in Matlab/Simulink platform. Transient equations for mass balance and energy balance are presented. During driving, the bed requires external heat source, which is planned to be supplied by rejected heat from proton-exchange membrane (PEM) fuel cell. Therefore, this study develops a system-level dynamic model of a PEM fuel cell that is capable of characterizing the mixed effects of temperature, gas flow and capacitance, with... 

The study of heat transfer using solid-liquid phase shifting has attracted much attention in applied engineering fields such as latent heat energy storage, building walls, waste energy recovery, battery thermal management, and more. Over the past few decades, the literature on phase shift has grown tremendously in terms of theory, laboratory, and numerical studies. Melting of phase change materials in rectangular chambers due to its wide range of engineering applications in fields such as casting, metallurgy, heat energy storage, and heat exchangers used in buildings, as well as aerospace issues including the use of These systems have been the subject of numerous studies on space missions 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... 

In this research, two important mechanisms were discussed including droplet generation and jumping mechanisms using electro wetting-on-dielectric. For these purposes, the finite element method (FEM) was used to solve the unsteady Naiver-Stokes equation. In addition, the level set method was applied to capture the interface between two phases. In the current study, first, droplet generation in a T-junction fluidic channel device was studied through using electro wetting actuation. The efficacy of electro wetting on the droplet generation frequency as well as droplet diameter is visible in a T-junction fluidic channel since after applying voltages, specified with non-dimensional electro... 

Nowadays, radical increase in energy consumption guides humankind to find and harvest some alternative energy resources. Between the energy resources that have ever been known, Solar Energy is the most traditional one and Solar Water Heaters (SWHs) are the most ancient tools that have been used to store this energy up to now. Regarding this issue, many researches have been done to investigate different aspects of SWHs and the most conventional type was Thermosyphon SWH system. In this study, our aim is to investigate the influence of Pulsating Heat Pipes (PHPs) application as a heat transfer tool to convey absorbed solar energy to hot water reservoir of a SWH. In order to do this research,... 

The water crisis caused by climate change and anthropogenic activities in Iran has affected the daily lives of the people, and since the agricultural sector has a large share of water consumption, greenhouse cultivation and indoor farming has been developing in this country, to improve water productivity. Considering that the main source of energy supply in greenhouses is fossil fuels, in this work, the possibility of improving Industrial Symbiosis (IS) between greenhouses and waste heat sources in industries by employing the Organic Rankin Cycle (ORC) has been studied, in order to meet the heating demand of greenhouses in a more sustainable and eco-friendly way.Based on that, by modeling... 

Considering problems related to energy, including high fuel prices, increasing demand, constraints, and environmental pollution, makes it clear that efficiency is one of the major problems in all over the world. Iran’s southern parts and those countries around Persian Gulf face serious shortage of drinking water. Moreover, on top of the other three types of energy production the need for drinking water is highly sensible. Therefore, the use of CCHPW System is the best solution in these areas. The purpose of this design is to empower the control capability of the combined systems over all factors and apply the necessary changes under different conditions. This endeavor requires a program to... 

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... 

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... 

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... 

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... 

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... 

A Lab-On-A-Chip is a micro-scale system whic h utilizes some micro-scale components in order to implement detection tests on samples. One of the most important components of a lab-on-a-chip device is the micro-mixer, which is responsible for appropriately mixing of samples in a short period of time. The biggest problem relevant to mixing in micro scales is that since as the viscous forces are dominant in micro scale and dimensions are small, it is impractical to mix fluids via turbulence, and consequently mixing process is performed by diffusion mechanism. Two major strategies are being used in order to improve the mixing performance and two groups of micro-mixers, passive and active types,... 

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... 

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... 

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.... 

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... 

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...