Sharif Digital Repository

One of the major reasons causing cracks in external surfaces of concrete arch dams are thermal loads. Therofore, in order to avoid instabilities due to function of thermal loads in association with hydrostatic and hydrodynamic pressures, a precise evaluation of temperature distribution through dam body is indispensable. In this study, effects of thermal loads mostly on upstream surface of Karun-3 concrete arch dam in Iran were examined using a 3-D finite element method considering water level fluctuations. Also the influence of operatvie boundry conditions in our problem which are water temperature, air temperature and solar radiation was precisely taken into account. Moreover, nonlinear... 

In this thesis to simulate the behavior of liquid engine Thrust chamber of hot gas from a quasi one dimensional code used when the effects of the heat transfer and friction in those terma. As well as during the regenerative channel is simulated by considering the equation’s of continuity, momentum and energy for one dimensional, effects of increase temperature, pressure drop, change the density of coolant flow resulting from the warming which is visible along the way to increase the accuracy of calculation of the thermal flux output of the engine, use a suitable model for unclear boiling in consideration of heat transfer coefficient used coolant flow it has been. As well as coupling of heat... 

Considering the limited number of works on investigation of solidification characteristics of Al-Zn-Mg-Cu cast alloys as well as the applications of this alloy system in aerospace industries, the solidification conditions of Al 713 alloy were investigated in this study. In order to achieve this goal, a number of experiments were designed and conducted including quantometry, thermal analysis, metallography and hardness measurements. In this thesis, effects of cooling rate on secondary dendritic arms spacing as well as solidification parameters including nucleation temperature, solidification time and temperature range, dendrite coherency point and formation temperature of intermetallic... 

Thermal analysis of concrete arch dams is always an important issue in designig these enormous concrete structures. The reason this issue mainly concerns arch dams and not gravity dams is because of little thickness of arch dams which makes them prone to cracking due to thermal loading. To solve any thermal problem we need boundary conditions. In arch dam case, these boundaries are the temperature of the upstream and downstream face of the dam which, depending on circumstances, can be in touch with water or air. Estimating air temperature is a fairly easy task when you have monthly mean temperatures. The challenging part is defining water temperature in any depth of the reservoir whenever we... 

These days, the heat transfer phenomena is an important issue in internal combustion engines design because of direct effects on the performance, efficiency and emission of engine. One of the main parts is cylinder head which contacts with hot gases in combustion chamber and expose high heat flux. In this thesis, cylinder head of Tiba engine modeled by three dimensional and transient thermal analysis. In this modeling in order to consideration the effect of fluid flow, different domain of cylinder head (water jacket, intake/exhaust ports) has been simulated and appended to the model. Also combustion phenomena modeled separately, and then the heat transfer coefficient in the surface of... 

The most important issues in massive concrete structures such as concrete dams are the increase in temperature due to heat generated by the dam Hydration of cement in concrete. Internal restrains are created from thermal gradient between the surface and the interior of the structure. External restrains are created from connections between structures and foundation for obstruct the movement of concrete structures due to temperature change. External restrains and internal creates tensile stresses in the concrete considerable, which can lead to thermal cracks in the structure. To prevent or minimize the possibility of cracks are examined thermal studies for the design of reinforced concrete... 

Radioisotope thermoelectric generator (RTG) is a kind of nuclear batteries, in which thermal energy resulting from the discharge of charged particles decayed of radioisotope, using thermoelectric arrays, can be converted to electrical energy. In this study, the different kinds of RTGs introduced and applications of them have been expressed. All types of radioisotopes used in RTGs have been reviewed and the most suitable of them in terms of maximum thermal power density and minimum dose rate have been selected. All types of thermoelectrics used in RTGs have been reviewed and the most suitable of them in terms of the range of temperature and maximum efficiency have been selected.
In this... 

Spent fuel assemblies are kept in spent fuel maintenance pools, designed at the vicinity of the reactor, after consuming. As capacity of these pools are limited, fuel assemblies should be transported to outside of the reactor building for maintenance. Transportation cask is used for this reason which is Russian type, named TUK-13, at Bushehr Nuclear Power Plant. The aim of this project is to ensure proper removal of heat from the transportation cask(TUK-13). For this purpose, numerical computational fluid dynamics method is used. The software used in this study is the Comsol. The temperature range suitable for any part of the chamber is different; but the most sensitive and the most... 

In this study, the effect of two main parameters, time and temperature, were investigated in the roasting process of zinc sulfide of Bafgh’s mine, and kinetics and the mechanism of the roasting reaction were examined, too. The oxidation process was performed in a muffle furnace in the presence of the oxygen of air atmosphere. The raw powder material (with the particle size of 74-250 micron) was poured in Alumina crucibles. The roasting process was run in eight temperatures of 650, 700, 750, 800, 850, 900, 950 and 1000 ◦C. Oxidation percent was calculated in six times of 5, 10, 15, 30, 45 and 60 minutes. The experiments were designed in a way that the effect of each parameter could be... 

This research has studied the kinetic and mechanism of partial reduction of hematite to magnetite via carbon monoxide gas. In addition, temperature and partial pressure of CO gas as two main parameters which influence the rate of the reduction process has been studied. In order to investigate the change in mass during the reaction, thermogravimetric analysis (TGA) has been applied and in order to evaluate the effect of the temperature and partial pressure of CO on the rate of the reduction, three different temperatures and two different ratios of CO/CO2 has been experimented. Three isothermal analysis in 390°C, 440°C, and 490°C in pure CO atmosphere and two isothermal analysis in 550°C with... 

Steel is a non-combustible material, but at high temperatures, steel structures, due to their diminishing yield strength, undergo a considerable visco-plastic deflection, which results in a reduction in their load bearing capacity. Thus, to increase safety against fire must be considered as an important objective in the design and construction of steel structures. One of the safety measures which can be taken against fire is to increase the resistance of the structure against heat by using heat-resistant coatings. This decreases the rate of transfer of heat to the structure, and must include the ‘structural members’ and ‘structural joints’. Due to the role of structural connections in... 

This thesis is a research corresponding to Super-Hydrophobic condensation substrates with Nanometer texture. In this study, the foresaid surfaces are fabricated by two methods that are Nano-composite paint and Electrophoretic coating. As a summary for the first method (the Super-Hydrophobic Nano-composite paint), the hybrid coating contains two mineral and organic phases; The organic phase is a two-part clear-coat polyurethane and plays the role as a polymer matrix in Nano-composite structure. Silica Nano-particles are the mineral phase and the two phases of Nano-composite have made connection with silane compounds. Also, surface-modification in Nano-particles for giving hydrophobicity... 

A significant portion of the substances used in the chemical industry are toxic and hazardous, posing major safety hazards. In this regard, studies on the flammability limits of flammable materials are important and necessary. Flammability limits are the range of fuel-oxidant mixtures that can lead to flame propagation. This project examines the flammability limits of different fuels. In this study, a set of fuels have been selected as the fuel world, and to select these compounds, their molecular structure as well as thermodynamic properties such as standard enthalpy of formation and standard enthalpy of combustion have been considered. It has been shown that by redefining the fuel world,...