Sharif Digital Repository

Global energy consumption is on a trajectory to surge by 50% by 2050, primarily driven by prevailing energy consumption patterns. Consequently, the imperative to innovate and develop novel energy sources, such as the utilization of recycled waste heat, has become paramount for the foreseeable future. In light of this, this paper delves into the transformative potential of employing Phase Change Materials (PCMs) for cooling Thermoelectric Generators (TEGs) and harnessing waste heat for productive purposes. The research investigates three distinct configurations to evaluate the efficacy of PCMs in enhancing thermal management. Configuration 1 exclusively relies on an active cooling fan, while... 

In this project a system of solar air collector and a storage tank containing of phase change materials has been modeled, examined and optimized. The collector model has been developed in the EES engineering software and also solar thermal potential has been calculated via MATLAB software and then imported to EES and with past air and ambient charectristics, the effective thermal temperature of solar air collector`s exhaust will be defined for six mid days of six cold months. In the coldest day of those six days storage model witch has been developed in MATLAB will be consumed to withdraw the models results and then system parameters go on a sensitivity analysis and a novel system goes for... 

One of the main components of any solar power plant is the heat storage. Implementing heat storage reduc-es the cost of power generation by increasing the capacity factor of the system. This Thesis aims to analyze the operation of heat storages by modeling latent heat
storage. In this regard, an efficient method named "Method of Characteristics" is utilized. Models developed based on this method are possible to be used for comparison, sensitivity analysis, and optimization due to their low computation time. Sensitivity analysis was carried out based on various parameters such as void fraction, fiUer material size. Results show that using latent heat storage, storage c-apacity is... 

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... 

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... 

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... 

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... 

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... 

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... 

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... 

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 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... 

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... 

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... 

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... 

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... 

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... 

The unique properties of phase change materials (PCMs), such as high latent heat and nearly constant phase change temperature, have made them a suitable option for use in thermal energy storage systems and thermal management systems. However, the low thermal conductivity of these materials has imposed limitations on their widespread use in industries. In this study, for the first time, the effect of injecting a boiling fluid (BF) into the PCM container to enhance heat transfer and accelerate the solidification process has been experimentally investigated. In this regard, paraffin wax and acetone have been selected as the PCM and the BF, and the effects of parameters such as the initial... 

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...