Sharif Digital Repository

One of the significant as well as fascinating utilization of thermoacoustic is combining heat pump and thermoacoustic refrigerator. By means of supplied heat from hear source, the heat pump generates acoustic power which will be absorbed by refrigerator and forwarded to the heat source afterwards. In other words, thermoacoustic systems, from the side of which heat is absorbed, produces chill in the opposite side. Due to the novelty as well as heavy and precise research requirements, these systems has been neither designed nor manufactured in our country yet. In this research a laboratory prototype from aforementioned systems has been constructed, thereby paving the way for enjoying and... 

Thermo-acoustic sience is the conversion of heat to power through the sound wave. Thermoacoustic engines for different reasons like easy making, not having moving parts and so high reliablibility of system is in attention for researchers. Also looped-tube thermoacoustic engines are very new in the world and sience and thechnology of them belong to a few companies and for different reasons are replacing different kinds of thermoacoustic engines.They have higher efficiency than other types. They can be made in large scales. They have a larger thermal range. In this research, the numerical study of one, two and four stage looped-tube thermoacoustic engines has investigated with the help of... 

In this dissertation, based on the method of recurrence plot and its application in dynamic system analysis we examine the behavior and dynamic analysis of a swirl burner. Though retrospective studies on thermoacoustic instability have been performed on single-blown premixed cone shape flames and several combustion systems but so far this method has not been considered for a real combustion system. There have also been more work on phenomena known as the flame separation from the burner (blowout) and its propagation into the burner (flashback), which is almost conscious of their process. In fact, selecting a single flame has been to eliminate the flame-flame interactions in the... 

Streaming has some applications in medical and industrial science. This phenomena can increase or decrease efficiency of an acoustic system. Deliberate streaming used to eliminate heat exchanger is an example of desired applications. In the most cases, secondary flow is an undesired issue. Streaming in thermal buffer tube (TBT) of thermoacoustic stirling heat engine (TASHE) has some unwanted effects. The main goal of author is to simulate numerically periodic field in TBT with axisymmetric geometry and study the effects of variating geometry and turbulence on the intensity of streaming. According to inaccessible boundary conditions in TBT of TASHE, firstly, the field is numerically solved... 

Thermoacoustic engines are a promising alternative to the conventional heat engines due to the absence of moving parts in the hot region and the small temperature difference required for operation. However, the traveling wave thermoacoustic engine configuration has a relatively lower efficiency due to a phenomenon called Gedeon streaming. In this regard, a jet pump might be used to lower the negative effects of Gedeon streaming. The jet pump, which is simply an element consisting of one or more tapered holes, induces an oscillating flow through the asymmetric device and hence resulting in a time-averaged pressure drop across it. As a result, by balancing this time averaged pressure drop with... 

In the last few decades, the consumption of fossil fuels and its increasing worldwide price on one hand, and the severity of global warming on the other hand have led researchers and engineers to invent and expand new cooling technologies. Cooling has the largest portion of energy consumption of households during the hot season of a year. In addition to high energy consumption, the common cooling systems utilize gases which are harmful for environment. Thermoacoustics is a new and recent technology which has arised from combination of acoustics and thermodynamics. In Iran, research in this new field was pioneered by Ghorbanian in Department of Aerospace Engineering at Sharif University of... 

Streaming is a phenomenon that is driven by acoustic oscillations and leads to the reduction of efficiency in thermoacoustic engines. Acoustic streaming induced by acoustic oscillations is a steady mass-flux of second order and can cause heat leak that greatly reduces efficiency. There are two types of streaming in thermoacoustic engines; Gedeon streaming and Rayleigh streaming. Gedeon streaming exists within the porous media and Rayleigh streaming occurs in the thermal buffer tube. Thermal buffer tube separates the hot heat exchanger from secondary cold heat exchanger. In this thesis, experimental study of Gedeon streaming and Rayleigh streaming has been accomplished by temperature... 

Carbon Nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic phenomena of these sound sources both in near and far field regions. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. Although pressure amplitude increases with increasing frequencies, maximum pressure amplitude reached in lower frequencies may become larger than its maximum amount at higher frequencies because of interference effects. Measurement of different surface area sources shows generation of sound waves in far field is independent of... 

Carbon nanotubes have special thermodynamic properties which makes suitable as a thermo-acoustic sound source. Recently it is shown that by using these nanotubes it is possible to generate strog sound waves in air or water. Experimental analysis of phenomenon can be complicated and expensive. Hence this fact, in this study using molecular dynamic simulation, numerical analysis of sound generation with CNTs in air and water is discussed. For this purpose, the required structue of the system is generated and it has reaced equilibrium. This process has been done for 6 different CNT and for each CNT there are 5 different distances between them. Althogether, 30 different cases has is used for... 

Traveling wave thermoacoustic prime mover is studied in this project. For this purpose, based on one dimensional thermoacoustic equations, thermoacoustic flow is modeled in each segment of thermoacoustic systems. Since regenerator is the most important segment in a traveling wave thermoacoustic prime mover, modeling of the flow in regenerator is considered as the primary motivation for this research. In order to model the thermoacoustic engines, governing 1D relations are simplified and developed. Moreover, to solve equations in regenerator, tortuous geometry of regenerator is approximated with the stack consisting of circular pores. Therefore, in this research stack relations has been used... 

Design and parametric study of a coupled thermoacoustic refrigerator system has been carried out based on thermoacoustic theories. The purpose of coupled thermoacoustic refrigerator design is to cool a container with small dimensions for use in cold storage above zero. The application of this refrigerator is where the waste heat of piston engines of distributed generation (DG) plants can be used as energy input. The design is based on the simplicity and low cost of the refrigerator. Therefore, the engine and refrigerator part of the coupled thermoacoustic refrigerator is enclosed in a resonator with a fixed diameter, which is closed on both sides of the resonator. Two standing-wave...