This paper describes progress towards the development of a large-capacity, singlestage, Stirling-type, pulse-tube refrigerator (PTR) for high temperature superconducting power applications. Specifically, the design and fabrication of an experimental PTR is described followed by a series of design modifications which have focused on optimization of the flow transition components the hot and cold ends of the pulse-tube. Computational fluid dynamic models are described and have been used to guide the design modifications. The impact of each modification on cooler performance is discussed. The cooler is instrumented with piston displacement sensors, high-frequency pressure sensors, and thermocouples along the regenerator wall, within the cold heat exchanger gas volume, and along the pulse-tube wall. These sensors provide some characterization of the flow distribution in the regenerator and pulse-tube.
This paper describes the design and preliminary experimental results for a large capacity (300W at 65 K) single-stage, Stirling-type pulse-tube. The regenerator, the critical component in the pulse-tube, was optimized via a parametric study accomplished using the REGENv3.2 program. The pulse tube system was subsequently designed using a 1st order model that calculates the pressure-flow characteristics of the system coupled with 2nd order models of the various internal loss mechanisms. An experimental pulse-tube system was fabricated based on this design; the pulse-tube apparatus allows simultaneous, high frequency measurement of instantaneous compressor piston position as well the instantaneous pressures at various locations in the system. In addition, the average temperatures along the regenerator, within the cold heat exchanger gas volume, on the cold heat exchanger surface, and along the pulse-tube are measured. This comprehensive set of measurements will allow a thorough evaluation and verification of the design model over a wide range of operating conditions including compressor stroke, frequency, charge pressure, and load temperature. This paper presents some preliminary experimental progress and compares the measured pressure-flow behavior with the design model predictions.
Future space-based systems will require long-life, active cryocoolers capable of achieving sub-10 K load temperatures. Currently, the available cryocooler technology at these temperatures is too massive and inefficient. In many cases, reliability is low and vibration high. An innovative hybrid cryocooler is being developed to address these concerns. The cooler directly interfaces a recuperative, reverse-Brayton, low-temperature stage with a regenerative, pulse-tube upper stage. This hybrid, multi-stage cryocooler has the potential to be an efficient and compact device capable of meeting the cryogenic cooling needs of future space-based systems. The concept of the hybrid cryocooler is reviewed briefly. Progress towards the development of the components within the hybrid system, including the pulse-tube stage, rectifying interface, recuperative heat exchanger, and turbine, is described.
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