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Search Publications by: Ray Radebaugh (Assoc)

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Displaying 76 - 100 of 167

Status and Recent Trends in Cryocooler Research

April 6, 2008
Author(s)
Ray Radebaugh
The five types of cryocoolers used to provide cryogenic temperatures for various applications are the Joule-Thomson, Brayton, Stirling, Gifford-McMahon, and pulse tube cryocoolers. Many advances in all types have occurred in the past twenty years that have

CALCULATED REGENERATOR PERFORMANCE AT 4 K WITH HELIUM-4 AND HELIUM-3

March 16, 2008
Author(s)
Ray Radebaugh, Yonghua Huang, Agnes O?Gallagher, John Gary
The helium-4 working fluid in regenerative cryocoolers operating with the cold end near 4 K deviates considerably from an ideal gas. As a result, losses in the regenerator, given by the time-averaged enthalpy flux, are increased and are strong functions of

Impedance Measurements of Inertance Tubes at High Frequency and Pressure

July 16, 2007
Author(s)
Michael A. Lewis, Ryan P. Taylor, Peter E. Bradley, Ray Radebaugh, Gershon Grossman, Zhihua Gan
Previous comparisons between measured and calculated inertance tube impedance were made at frequencies below 70 Hz and average pressures below 3 MPa. In this paper, we present results on similar comparisons for frequencies up to 150 Hz and average

MODELING AND EXPERIMENTS ON FAST COOLDOWN OF A 120 Hz PULSE TUBE CRYOCOOLER

July 16, 2007
Author(s)
Srinivas Vanapalli, Michael A. Lewis, Gershon Grossman, Zhihua Gan, Ray Radebaugh, H.J. M. ter Brake
High frequency operation of a pulse tube cryocooler leads to reduced regenerator volume, which results in a reduced heat capacity and a faster cooldown time. A pulse tube cryocooler operating at a frequency of 120 Hz and an average pressure of 3.5 MPa

EQUATION OF STATE AND THERMOPHYSICAL PROPERTIES OF HELIUM-3

April 3, 2007
Author(s)
Yonghua Huang, G.B. Chen, V. Arp, Ray Radebaugh
Experimental data of the thermophysical properties of 3He were mined into a searchable database. Equilibrium equations along the vapor-liquid and liquid-solid lines were proposed. A general equation of state for normal fluid 3He based on the Debye specific

THE DEBYE FLUID STATE EQUATION

April 2, 2007
Author(s)
V. Arp, Yonghua Huang, Ray Radebaugh, G.B. Chen
We describe a new form of a fluid state equation, based on a conceptual extrapolation from the Debye equation for the specific heat of solid materials. The Debye characteristic temperature, theta, which is nominally a constant for solids, becomes a

120Hz Pulse Tube Cryocooler for Fast Cooldown to 50K

February 13, 2007
Author(s)
Srinivas Vanapalli, Michael A. Lewis, Zhihua Gan, Ray Radebaugh
A pulse tube cryocooler operating at 120 Hz with 3.5 MPa average pressure achieved a no-load temperature of about 49.9 K and a cooldown time to 80 K of 5.5 minutes. The net refrigeration power at 80 K was 3.35 W with an efficiency of about 22.6% of Carnot

Characterization of Inertance Tubes Using Resonance Effects

June 14, 2006
Author(s)
Michael A. Lewis, Peter E. Bradley, Ray Radebaugh, Zhihua Gan
Inertance tubes can be characterized by their inertance, compliance, and resistance. All three of these impedance components are present during normal measurements of inertance tube impedance. As a result, in comparing experimental results with models it

Proposed Rapid Cooldown Technique for Pulse Tube Cryocoolers

June 14, 2006
Author(s)
Ray Radebaugh, Agnes O?Gallagher, Michael A. Lewis, Peter E. Bradley
Some cryocooler applications, such as those for military operations dealing with high temperature superconducting (HTS) magnets, motors, or generators, require faster cooldown times than what can normally be provided with a cryocooler designed to

Inertance Tube Optimization for Pulse Tube Refrigerators

April 27, 2006
Author(s)
Ray Radebaugh, Michael A. Lewis, Ercang Lou, John M. Pfotenhauer, G. F. Nellis, L. F. Schunk
The efficiency of regenerative refrigerators is generally maximized when the pressure and flow are in phase near the midpoint of the regenerator. Such a phase relationship minimizes the amplitude of the mass flow for a given acoustic power flow through the

Regenerator Operation at Very High Frequencies for Microcryocoolers

April 27, 2006
Author(s)
Ray Radebaugh, Agnes A. O'Gallagher
The size of Stirling and Stirling-type pulse tube cryocoolers is dominated by the size of the pressure oscillator. Such cryocoolers typically operate at frequencies up to about 60 Hz for cold-end temperatures above about 60 K. Higher operating frequencies

Heat Transfer Issues in Cryogenic Catheters

November 7, 2005
Author(s)
Ray Radebaugh
Catheters with diameters of 3 mm or smaller are capable of accessing many internal organs through arteries and veins. They provide the medical community with tools to operate on internal organs without the need to cut through the body to gain access. As a