Sharif Digital Repository

Shortage of energy sources in the new decade along with the increasing level of greenhouse gas emissions urges researchers in the field of energy to explore for the new source of energy as well as seeking for methods for usage of available energy resources more efficiently. Therefore, development of building with low level of energy usage may significantly reduce the need for grid energy. This can be met with new construction materials to reduce the energy consumption, using renewable energies sources such as solar and wind as well as design and development of materials with capability to store energy. The use of materials which can store energy and release it when needed has been considered... 

Phase change materials have been of great interest due to their ability to save and restore energy in low temperature ranges. PCM can save and release energy in a constant temperature which leads to save in energy. These materials have been widely used in solar cells, storage tanks, human body and buildings. Applications of PCMs have been discussed in the last chapter of this thesis. To study the effect of PCM, a room with bricks, chalk, insulator and also PCM is assumed. Abovementioned room in summer and winter of Tehran with south-north and west-east walls has been simulated in COMSOL. Effects of air’s convection in the room and brick’s holes have been investigated in simulation and... 

Rammed earth (RE) structures are getting popular due to sustainability, environmental-friendly and economic advantages. Various studies have investigated the mechanical behavior and the energy performance of RE materials. However, little is known about the fracture behavior of RE materials. In this research, the fracture properties of RE materials containing different percentages of various stabilizers were investigated using a modified wedge splitting test. The stabilizers were cement, pozzolan, microsilica, glass-fiber, guar-gum and phase change material. In addition, the effect of stabilizers on the microstructure and the phase composition was inspected using scanning electron microscope... 

Desalination of seawater is one of the best solutions for freshwater supply. Solar desalination is an appropriate way to desalinate seawater. The main disadvantage of solar desalination systems is low daily production. Considering the free radiative cooling potential, the purpose of this project is the increment of the daily yield of solar still by enhancement of condensation process. For transferring cooling potential of radiative cooling from nighttime to the daytime, phase change materials (PCMs) are used. Two types of condensers are fabricated in this project. One of them uses ambient air as a thermal sink and the other one uses radiative cooling which is saved in PCM. Describing... 

Heat transfer associated with phase change occurs in many physical phenomena. One of the ways of thermal energy storage is the use of latent heat phase change. Therefore, it is important to know the thermal performance of phase change material. In this research, the aim is to investigate the process of phase change of a system consists of two immiscible phase change materials and the comparison of this system with a system consists of one phase change material. The experiments with the two materials system is conducted in two ways. In the first state, that is the normal state, denser material is placed in the bottom and in the second state, denser material is placed in the top. Constant heat... 

One of the different methods of heat transfer, is pool boiling process. In this method, the operating fluid starts to boil on a hot surface whose temperature is more than boiling point of the fluid. Based on difference between between surface temperature and fluid boiling point, amount of heat flux from hot surface to fluid and fluid behavior will be different. In recent years, many researchers have tried to improve the amount of heat transfer in the boiling process by using various methods such as nanoparticle addition or using magnetic field.Latent heat is thermal energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process, usually a first-order... 

Providing fresh water, ending fossil fuels, using renewable energy and achieving a clean biological environment in different parts of the world especially in Iran beside having access to many saline water sources, Shows the need for research in the field of solar still desalination. The goal of current study is to increase the performance of the solar still system through the use of an energy storage system and an additional condenser. Adding an additional condenser to a conventional solar still lead to an increase in the rate of evaporation and consequently increase the production of the system. Also, by collecting distilled water from the sidewalls, the amount of water produced... 

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... 

To reduce material consumption needed in production as well as avoiding thousands of tons of contaminations produced by spent materials in the battery industry, recycling was taken into consideration. In this study silica was recycled from spent lead-acid battery separators by the pyrolysis process. silica along with high-density polyethylene (HDPE), can be used as supporting material for fabricating form-stable phase change materials (FSPCM). FSPCMs are of great ability to be used as thermal energy storage (TES) in different parts of a building e. g. wallboards to reduce energy consumption. In this line, an eutectic mixture of lauric acid, palmitic acid and paraffin with the melting point... 

Nowadays energy consumption increases in our daily life and incredibly enhancement of growth rate can be seen recent years. Hence, the use of renewable energy is prioritized. Solar energy is one of the choices because it is free and available. In this research, it has been tried to get electrical and thermal power at a reasonable cost both during the day and night. The system is equipped with a linear parabolic concentrator with a collector installed in the center of the concentrator which has been installed on its faces photovoltaic cells and thermoelectric modules, and five different systems have been tested with different components. Also, the paraffin has been used as a phase change... 

In solar systems, the required space and cost, the impossibility of continuous access to energy, energy storage and optimal use of the received energy are the basic parameters and issues. Therefore, with the knowledge of these cases, proposing ideas and approaches to study the possibility of reducing the above mentioned issues are of the main objectives of this research. In solar thermal systems and solar electrical systems, the collector and photovoltaic panels are the main components, respectively. However, the studies show that there are issues regarding the existing collectors and photovoltaic panels, e.g. the flat-plate type which is most used in solar systems, and the basis is not... 

Buildings are responsible for 40% of total energy consumption worldwide. A significant portion of this energy contributes to building temperature control, and energy storage is an effective way to reduce energy consumption and to levelize the supply of heat load. A solution for reducing energy consumption in the building is to increase the thermal inertia of the building and to store energy using smart materials in the building components. Materials with phase change can stabilize the internal temperature of the building.In the present study, model is exmined with the help of modeling the thermal behavior of a room in Tehran in summer, using MATLAB software. The problem is solved by the... 

The low melting and solidification rates of phase change materials, which traces back to their low thermal conductivity coefficient, has led the application of these materials to face limitations. In this study, it is attempted to enhance the energy storage process in phase change materials for a complete charge-discharge cycle using a novel method called SFD-IBF. Throughout this novel technique paraffin and acetone are used as phase change material and intermediate boiling fluid, respectively. In the solidification process, there is no direct contact between the cold source and the molten paraffin, while acetone, as an intermediate fluid, is being boiled via adsorbing paraffin’s heat and... 

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... 

Improving the discharge process of phase-change materials (PCMs) is of great importance. In this study, the process of acetone drop impact on molten paraffin, as a direct-contact solidification method, is experimentally investigated. Four Weber numbers (corresponding to heights of 10, 20, 30, and 40 cm) for the acetone drop and six surface temperatures (66, 68, 70, 75, 80, and 90 °C) for the molten paraffin are considered. As the acetone drop impacts the molten paraffin, the drop absorbs heat from the melting paraffin and boils, solidifying a portion of the molten paraffin. Two important parameters that govern the acetone drop dynamics and the solidification of the molten paraffin are the... 

In this study, a vapor-compression cooling system utilizing different PCMs has been studied whereby the electricity consumption peak load is shifted. More specifically, the dynamic performance of cooling systems with and without using PCM is evaluated for the hottest day of the year. The proposed system uses the cooling energy to freeze, or “discharge” the PCM during nighttime when the cooling load is minimally needed and uses the stored thermal energy during the peak load hours by melting, or “charging” the PCM. This leads to better performance during peak load hours when higher cooling loads are needed. Different PCMs including Oleic acid, SP224A, CL, CaCl2.6H2O have been investigated. The... 

As producing and consuming of natural gas has increased in recent years, improving natural gas distribution and transfer network systems has become vital. Pressure reduction station (PRS) is an important part of the natural gas network. Common PRSs are facing two issues: first is the pressure reduction technology, which is throttling valve that destroys the exergy of the high pressure flow. The solution is to utilize turbo-expander instead which can recover the energy. Second is the preheating technology which is boiler and water bath heater in the common systems that cause environmental problems. Using solar collectors is one of the best solution based on the literature. Since the solar... 

Lithium-ion batteries have the ability to store a significant amount of energy and work at high power, which has led to the wide spread of their use in various industries. In high-power applications, battery heat management increases lifespan, safety, and reduces battery power loss. In this study, the heat management of a very common and widely used 18650 battery using multi-layered phase change material has been investigated. The reason for using multiple layers is that each phase change material has its own weaknesses in addition to its advantages. It is expected that with the proper use of several phase change materials in the thermal management system, the materials will reduce the...