Sharif Digital Repository

Different strategies for the treatment and disposal of petroleum and biological sludge found in the treatment and reuse unit of Arak Petroleum Refinery have been studied in the present study. To this end, the resources found in the literature corresponding to the different fields of sludge treatment were studied and a summary of them which was required by this research was mentioned in the thesis. Considering the problems bound to the wastewater treatment unit of this refinery plant and the previous studies, two completely separate strategies were devised. The first one concerns petroleum and biological sludge being produced continuously. The method of aerobic fixation of petroleum sludge by... 

In this project, the melting, solidification and remelting processes and also, the epitaxial growth of thin molten layer on the solidified crystalline substrate is studied using molecular dynamics simulation for the aluminum as an instance for the fcc metals. Sutton-Chen potential is used for energy calculations; the modified version of verlet algorithm is used for determination of position and velocity of atoms; and the berendsen algorithms are used as thermostat and barostat. The effects of pressure and temperature changing rate on the melting and crystallization temperatures and the crystal structure are investigated. The crystal structure of the system is examined using radial... 

In this study, our objective is to simulate the growth of frost for humid air passing through pressure regulators. The study is carried out in two main stages. First, we use an empirical method to model the formation of frost for a humid-air passing over a flat plate. The model is a semi-2D one and that it is limited to predict the frost growth at a particular station along the plate, considering the local flow heat transfer parameters. We show the validity of results comparing with available experimental data. Second, we numerically simulate the frost formation and growth for a humid air passing between two parallel plates. In this regard, the semi empirical method is suitably coupled with... 

Porous medium is a material consisting of a solid matrix with an interconnected void. A polymer is a large molecule composed of many repeated subunits, known as monomers; Polyurethane is a type of polymer which has many uses. The aim of this research project is to investigate the effective factors in polyurethane polymer injection and the behavior of this material during the foaming in cavities with different soil porosities (0.15 < φ < 0.4). Parameters such as thermal boundary conditions and the soil material that could be effective in solidification of polyurethane are analyzed, numerically using FLUENT software. A simplified model for foaming is presented in this study which can be used... 

In the process of Additive manufacturing for metals, the ability to predict and control the microstructure can reduce the need for subsequent heat treatment and accelerate the component quality assessment process. The ability to predict and control the microstructure of materials in the laser deposition method needs to understand the thermal conditions during the solidification process. For this purpose, the present study investigated the relationship between cooling rate and temperature gradient during local solidification, and control parameters of the laser deposition process such as power, beam radius, scanning speed and strategy of laser, ambient temperature and preheating temperature.... 

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... 

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... 

Additive manufacturing can be considered as a revolution in the manufacturing industry. The unique capabilities of this technology have led to the removal of many obstacles to the construction of complex and special parts. In this study, with the aim of further understanding how the gradient region is formed, the possibility of detecting the microstructure and finally the properties of the gradient piece made, a solidification process has been simulated in direct metal deposition. The results of this study include calculating the heat distribution during the process and obtaining a thermal history of the fabricated part, calculating the dimensions of the molten pool and the heat affected... 

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...