Sharif Digital Repository

The lubricating oil is commonly used to cool down the moving parts of turbine gas systems. In many applications, this oil is cooled down using a recirculating water circuit. The water is then cooled down using an air-cooled heat exchanger. Any deficiency in aerothermodynamic design of such heat exchanger would result in high temperature of gas turbine moving parts such as bearings. Obviously, this mal-performance has adverse effect on the lifetime of these parts and their maintanence aspects. Since the good performance of air-cooled heat exchanger has numerous advantages for the performance of related gas turbine unit, it is mandatory to design these heat exchangers in minimum sizes and... 

Tomography offers a unique opportunity to unravel the complexities of the internal structure of an object without the need to invade it. There are various methods for this reason, in which all of them occupy wave or energy,ffiduction for imaging inside an object. Since the tomography plays a vital role in medicine and industry and present methods have limitation and difficulties to operate, the necessity for developing it has been inevitable. In this thesis a new tomography method has been presented in which uses inverse heat conduction for estimating unknown object with heat conductivity k2 inside a known domain with heat conductivity k 1 • For this purpose temperature is measured at... 

This paper numerically studies the convection heat transfer enhancement of a developing two dimensional laminar flow in a pipe partially filled with porous materials. One of the most important effects of the systems with porous materials in them, is that they can improve some heat transfer components if they be used in a proper way. This study has been performed under both local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) conditions. Two energy equations are used in non-thermal equilibrium condition between fluid and porous material. Darcy-Brinkman-Forchheimer model is used to model the flow inside the porous medium. The effects of different parameters such as, Darcy... 

As a result of fission reaction in a nuclear reactor, the produced high neutron flux would affect the material of Reactor Pressure Vessel (RPV). This neutron radiation has a detrimental impact on the mechanical properties of the RPV material such as hardening (or embrittlement) while neutrons are absorbed by the material. A major concern in embrittled RPVs is propagation of critical flaw causing through-wall cracks. Some transients leading to overcooling of RPV intensify the propagation of theses cracks and result in thermal load on RPV, known as Pressurized Thermal Shock (PTS). Such situation could be created in case of Emergency Core Cooling System (ECCS) actuation which leads to injection... 

One main problem in many numerical simulations is the lack of sufficient infrastructure data to precisely model and analyze the flow through complex geometries. Since experimental procedures are generally very expensive; and sometimes impossible, it becomes necessary to find alternative ways such as numerical approaches to predict the flow behavior through complex geometries. The heat exchangers can be categorized as geometries with complex configuration and apparently expensive to solve numerically. They are widely used in different industries including the aerospace. The restrictions in design and implementation of aviation’s heat exchangers have promoted the related companies to converge... 

Todays, heat recovery steam generator (HRSG) systems are used extensively in combined power plant cycles (consisting of Rankine cycles and Brighton gas cycle) to maximize their efficiencies. The role of HRSG is essential in providing additional energy needed in the steam cycle part. The HRSG has many pipes or harps. They recover the heat from the incoming gas from the gas turbine outlet, which may be boosted up by the duct burner unit. The main challenge in simulating heat recovery units such as tube bundles is to provide ultra-large and cost-efficient grids. In such situations, alternative models are used to simplify the simulation of the steam generator in full scale, including the... 

High temperature modular reactors (HTR) are the most likely next generation reactors that will meet future energy needs. Their inherent safety is the most attractive feature of this type of reactors, and along with that, we can mention the ease of their design, operation and maintenance. Since the reactor is safe in the event of an accident, without activating any external source of security, this reactor is considered intrinsically safe. Despite this inherent property, the reactor is only affected by its physical characteristics, and therefore, many dangerous situations are prevented.The inherent safety feature of this reactor is completely dependent on its proper design. The power density... 

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... 

One of the steps in the production of nuclear fuel pellets used in the core of a nuclear reactor is sintering. Sintering means the consolidation of a pressed powder sample into an integrated solid. This process can be done in different ways, such as traditional sintering, microwave, spark plasma, etc. In the process of fabrication of nuclear fuel pellets, after producing uranium dioxide in powder form and making corrections on the size distribution of powder grains, it would be nolded and then sintered. In this research, the temperature evolution of the green pellets introduced to microwave heating were investigated. In this report, a brief overview of the principles of microwave heating is... 

Numerical three-dimensional simulation of the entire regions of a gas turbine blade, including hot gas flow over the blade surface, conduction heat transfer within the blade metal, and coolant flow through the Internal cooling System, is highly time-consuming and expensive. Therefore, one-dimensional internal flow simulation is one of the main objectives of this research to address the limitations of commercial software in predicting the temperature distribution along the cooling path. In this study, a one-dimensional in-house simulation code is developed to simulate the coolant flow inside the cooling channels of the internal cooling system of the blade. Additionally, using artificial...