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Title Periodic flow physics in porous media of regenerative cryocoolers
Publication Date
Date Accessioned
Degree PhD
Discipline/Department Mechanical Engineering
Degree Level doctoral
University/Publisher Georgia Tech
Abstract Pulse tube cryocoolers (PTC) are a class of rugged and high-endurance refrigeration systems that operate without moving parts at their low temperature ends, and are capable of reaching temperatures down to and below 123 K. PTCs are particularly suitable for applications in space, guiding systems, cryosurgery, medicine preservation, superconducting electronics, magnetic resonance imaging, weather observation, and liquefaction of gases. Applications of these cryocoolers span across many industries including defense, aerospace, biomedical, energy, and high tech. Among the challenges facing the PTC research community is the improvement of system efficiency, which is a direct function of the regenerator component performance. A PTC implements the theory of oscillatory compression and expansion of the gas within a closed volume to achieve desired refrigeration. An important deficiency with respect to the state of art models dealing with PTCs is the limited understanding of the hydrodynamic and thermal transport parameters associated with periodic flow of a cryogenic fluid in micro-porous structures. In view of the above, the goals of this investigation include: 1) experimentally measuring and correlating the steady and periodic flow Darcy permeability and Forchheimer’s inertial hydrodynamic parameters for available rare-Earth ErPr regenerator filler; 2) employing a CFD-assisted methodology for the unambiguous quantification of the Darcy permeability and Forchheimer’s inertial hydrodynamic parameters, based on experimentally measured steady and periodic flow pressure drops in porous structures representing recently developed regenerator fillers; and 3) performing a direct numerical pore-level investigation for steady and periodic flows in a generic porous medium in order to elucidate the flow and transport processes, and quantify the solid-fluid hydrodynamic and heat transfer parameters. These hydrodynamic resistances parameters were found to be significantly different for steady and oscillatory flows.
Subjects/Keywords Regenerator; ErPr; Nusselt; Porous media; Pore level; Periodic flow; Oscillatory flow; Darcy permeability; Forchheimer; Hydrodynamic; Thermal dispersion; Conjugate; Heat transfer; CFD; Pulse tube; Cryocooler; Cryogenics; Physics; Rare-Earth; Steady flow; Low temperature engineering; Materials at low temperatures; Porous materials Thermal properties; Porous materials
Contributors Ghiaasiaan, S. Mostafa (advisor); Desai, Prateen (committee member); Walker, Mitchell (committee member); Wilhite, Alan (committee member); Haynes, Comas (committee member); Radebaugh, Ray (committee member)
Language en
Country of Publication us
Record ID handle:1853/49056
Repository gatech
Date Indexed 2020-05-13
Issued Date 2013-05-23 00:00:00
Note [degree] Ph.D.;

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…List of cryocooler applications in various industries [2]. 17 Table 2.1: PTR developmental milestones [4]. 24 Table 2.2: Summary of Cha’s results [11]. 69 Table 3.1: Summary of tested regenerators. 74 Table 3.2…

…basic PTC schematic [6]. 11 Figure 1.6: Orifice pulse tube Cryocooler schematic [6]. 13 Figure 1.7: Inertance-tube pulse tube Cryocooler schematic [6]. 13 Figure 1.8: Thermal coupling (right) and fluid…

…in these temperature ranges. A particular type of cryogenic engineering application is a cryocooler, which is utilized for removing heat loads at very low temperatures and hence thermally managing the overall system that the cryocooler is employed on…

…operate in oscillatory flow. In oscillatory flow, the working fluid is periodically heated and cooled as it 2 undergoes small displacements over the course of a cycle. Also, a significant portion of the overall cryocooler system and particularly the…

…fluid, typically a gas, within a closed volume to achieve desired refrigeration. Regenerators and pulse tubes are often viewed as the two most complex and essential components of cryocoolers, where the regenerator is arguably the most vital cryocooler

…to the regenerator, where friction and thermal non-equilibrium between the fluid and the solid structure are detrimental to the performance of the regenerator and may thus play crucial roles. The efficiency of a regenerative cryocooler is dependent on…

…Stirling thermodynamic cycle, where the working fluid is subject to a series of compressions and expansions in periodic flow to complete its cyclic process. Figures 1.2-1.3 show schematics of the different common cryocooler types and diagrams of the ideal…

…fluid processes were steady and ideal, the device would fail to function [Organ (1992, [7])]. Other types of pulse tube cryocoolers include the orifice pulse tube cryocooler and the inertance-tube pulse tube cryocooler