Sharif Digital Repository

First and second law analyses of the pulse tube refrigerator cycle are performed in the present thesis. In this respect, mass, momentum and energy balance equations are employed to derive the system of governing equations. Three models have been resulted depending on the employed theoretical model to analyze the pulse tube and thermal regenerator sections. In the first model, the tube section governing equations have been descritised and finite volume technique has been employed to solve the equations. In the regenerator a linear trend was assumed for the pressure and temperature to complete the solution procedure. To improve the regenerator model, harmonic approximation technique has been... 

Multi stage Pulse Tube Cryocoolers (PTCs) have found the interest of researchers due to its reliability, long life and absence of moving part. This thesis represents a comprehensive numerical simulation method to investigate one and two stage PTC. All components of the PTC are modeled employing the nodal analysis technique to discretize the mass, momentum and energy conservation equations. SUTPTC code has been developed in cryocooler laboratory of Sharif University of Technology (SUT) to analyze and optimize one and two stage cryocooler performance. The SUTPTC code has been validated with the existing experimental data. Employing the proposed code, the effect of precooling temperature, the... 

There are numerous ways available to achieve low temperatures that cryocoolers might be among the most important of them. In the meantime, the pulse tube refrigerator has a special place due to its simple geometry and not be using any moving parts. This simple property make the pulse tube refrigerator one of the most popular methods to achieve low temperatures. Nowadays, a pulse tube refrigerator is used for cooling in the range of 4 to 123 Kelvin in two form of one-stage and two-stage and up to an approximate power of 1 KW. Today, due to the temperature and the amount of power required for cooling, as well as the time it takes to reach that temperature, this chiller is used in medical,... 

Pulse Tube Refrigerator (PTR) has an exceptional feature among all similar refrigerators, because of its unique characteristics such as long lifetime, compact size and no moving parts in low temperature. Despite of all these advantages because of its low efficiency, many researchers are trying to optimize performance of this refrigerator. Most of these efforts are based on one-dimensional simulation of the system. In this thesis, a two-dimensional analysis is performed to study the nature of flow field in an Inertance Tube Pulse Tube Refrigerator (ITPTR). This analysis is based on a numerical modeling of an entire ITPTR. To reach this purpose the two-dimensional form of mass, momentum and... 

Helium gas is the working fluid in common Pulse Tube Refrigerators (PTRs) due to its brilliant properties in reaching cryogenics temperature as low as 4 K. Generally ideal gas equation of state has been used to evaluate thermodynamic performance of He. However using ideal gas equation of state for He in 10 bar and 5 K causes considerable error on estimation of density. The objective is to use real gas equation of state for temperatures near zero Kelvin. This approach makes an accurate prediction of PT cooling capacity and COP. In this thesis the objective is to realize the most relevant equations of state describing the proper behavior of He in the regions of operating point of PTR. Later on... 

Pulse tube refrigerator due to the relatively high efficiency, high reliability of linear compressor and the absence of moving parts in the cold area is known as one of the best options to generate up to one kW of cooling power at temperatures from 4 to 123 K. More recently, the use of the device at a temperature of about 150 K, makes use of it even outside of cryogenic temperature. The most important part of the device is regenerator, so understanding the nature of the flow and interaction of gas and solid network in the retrievers is necessary. In this study, Inertance pulse tube refrigerator (IPTR) is simulated using Ansys Fluent in two different conditions. In the first condition the...