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You searched for subject:(Cryogenic Cooling Systems). Showing records 1 – 2 of 2 total matches.

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University of Kentucky

1. Mohammed, Anwaruddin. ACHIEVING ULTRAFINE GRAINS IN Mg AZ31B-O ALLOY BY CRYOGENIC FRICTION STIR PROCESSING AND MACHINING.

Degree: 2011, University of Kentucky

This thesis presents results from the application of cryogenic cooling on multiple-pass friction stir processing and the subsequent orthogonal machining on friction stir processed and as-received Mg AZ31B-O disks, and shows their combined effects on microstructure and microhardness values. A simple friction stir tool, a specially designed fixture and liquid nitrogen are used to perform multiple-pass friction stir processing experiments on Mg AZ31B-O alloy. The friction stir processed and as-received sheets are then made into disks for the orthogonal machining experiments. This study analyzes the microhardness, microstructure changes by cryogenic friction stir processing and the effect of machining conditions such as dry, MQL and cryogenic and cutting parameters on the Mg AZ31B-O alloy. Four different speeds and three different feed rates are used for the orthogonal machining experiments. The effects of stirring parameters such as the translational feed, rotational speed, cooling conditions and the machining parameters are studied. The resulting microstructure and microhardness from these processes hold a key to the mechanical properties of the alloy. This analysis would help to understand and evaluate the specific aspects of grain size and microhardness that influence the fatigue life of a component.

Subjects/Keywords: Friction Stir Processing; Cryogenic Cooling; Orthogonal Machining; Microstructure; Microhardness; Other Operations Research, Systems Engineering and Industrial Engineering; Systems Engineering

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APA (6th Edition):

Mohammed, A. (2011). ACHIEVING ULTRAFINE GRAINS IN Mg AZ31B-O ALLOY BY CRYOGENIC FRICTION STIR PROCESSING AND MACHINING. (Masters Thesis). University of Kentucky. Retrieved from https://uknowledge.uky.edu/ms_etds/1

Chicago Manual of Style (16th Edition):

Mohammed, Anwaruddin. “ACHIEVING ULTRAFINE GRAINS IN Mg AZ31B-O ALLOY BY CRYOGENIC FRICTION STIR PROCESSING AND MACHINING.” 2011. Masters Thesis, University of Kentucky. Accessed October 25, 2020. https://uknowledge.uky.edu/ms_etds/1.

MLA Handbook (7th Edition):

Mohammed, Anwaruddin. “ACHIEVING ULTRAFINE GRAINS IN Mg AZ31B-O ALLOY BY CRYOGENIC FRICTION STIR PROCESSING AND MACHINING.” 2011. Web. 25 Oct 2020.

Vancouver:

Mohammed A. ACHIEVING ULTRAFINE GRAINS IN Mg AZ31B-O ALLOY BY CRYOGENIC FRICTION STIR PROCESSING AND MACHINING. [Internet] [Masters thesis]. University of Kentucky; 2011. [cited 2020 Oct 25]. Available from: https://uknowledge.uky.edu/ms_etds/1.

Council of Science Editors:

Mohammed A. ACHIEVING ULTRAFINE GRAINS IN Mg AZ31B-O ALLOY BY CRYOGENIC FRICTION STIR PROCESSING AND MACHINING. [Masters Thesis]. University of Kentucky; 2011. Available from: https://uknowledge.uky.edu/ms_etds/1


Indian Institute of Science

2. Gurudath, C S. Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler.

Degree: PhD, Faculty of Engineering, 2018, Indian Institute of Science

This work is concerned with the design, development and performance evaluation of an inertance Pulse Tube Cryocooler (PTC). The main components of a PTC are the compressor, regenerator, pulse tube and inertance tube coupled to a reservoir. The inertance tube is a key component that affects the pressure and mass flow and phase shift between them and hence the performance. In conjunction with the compressor, it also plays a strong role in determining the frequency of operation. The PTC is designed based on system level numerical models (SAGE and DeltaE), component level thermo-acoustic models (DeltaE) of inertance tube and regenerator and experimental data of earlier fabricated Stirling coolers. As a starting point, an inertance tube with a diameter of 3 mm and 3.1 m long was chosen through component level analysis that provides phase shift of around 50 degrees at a pressure ratio of 1.1 for an acoustic power of about 4 W (in order to achieve 1 W of net cooling at 80 K) at 25 bar mean pressure and 60 Hz. From this inertance tube geometry, an estimate of the mass flow rate at the cold heat exchanger is obtained. Based on this mass flow rate, the initial dimensions of the pulse tube and regenerator are arrived at. A parametric study using system level model is carried out to obtain the maximum COP by varying inertance tube length and regenerator diameter. A flexure bearing compressor consisting of moving coil linear motor coupled to a piston is designed for the above cold head. Based on the above design considerations, the PTC compressor and cold head are fabricated and assembled. The PTC is charged with helium at mean pressure of 25 bar and instrumented with pressure and position transducers, temperature sensors and a skin-bonded heater for simulating the heat load on the cold head. Experimental data for the PTC were obtained with two different inertance tube lengths for different frequencies of operation. The cold head temperature exhibited a minimum with respect to the frequency. This optimum frequency shifts towards lower frequency with increased length of the inertance tube. The experimental data clearly shows that with different inertance tube lengths the optimum frequency locates itself for obtaining zero phase shift at the middle of the regenerator. It is observed that the optimum frequency is closely linked to the natural frequency of the pressure wave in the inertance tube suggesting a standing wave within the inertance tube with the pressure node at the reservoir. Thus the inertance tube is found to be analogous to a quarter wave resonator in a thermo-acoustic device. It may thus be possible to pre-fix an operating frequency for a given PTC cold head by choosing an inertance tube length close to quarter wave resonator length. This study has given insights on the phase shift between pressure and mass flow rate governed by the inertance tube and the connection between the optimum and natural frequencies which can be used for better design of PTCs. Advisors/Committee Members: Narasimham, G S V L (advisor).

Subjects/Keywords: Stirling Cryocooler; Inertance Pulse Tube Cryocooler; Pulse Tube Cryocooler; Cryogenic Cooling Systems; HighFfrequency Cryocooler; PTC-1; PTC-2; Mechanical Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Gurudath, C. S. (2018). Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3739

Chicago Manual of Style (16th Edition):

Gurudath, C S. “Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler.” 2018. Doctoral Dissertation, Indian Institute of Science. Accessed October 25, 2020. http://etd.iisc.ac.in/handle/2005/3739.

MLA Handbook (7th Edition):

Gurudath, C S. “Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler.” 2018. Web. 25 Oct 2020.

Vancouver:

Gurudath CS. Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2018. [cited 2020 Oct 25]. Available from: http://etd.iisc.ac.in/handle/2005/3739.

Council of Science Editors:

Gurudath CS. Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler. [Doctoral Dissertation]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3739

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