Investigation of Flow Nonuniformities in a Large 50 K Pulse Tube Cryocooler

Abstract

A single-stage pulse tube cryocooler was optimized to provide 50 W of net refrigeration power at 50 K when driven by a pressure oscillator that can produce up to 2.8 kW of acoustic power at 60 Hz. The cryocooler was designed with the ability to provide rapid cooldown. The rapid cooling technique makes use of a resonant phenomenon in the inertance tube and reservoir system to decrease the flow impedance and thereby increase the acoustic power and refrigeration power in the system when the cold end is near room temperature. Initial experimental data produced no-load temperatures of about 100 K and showed large azimuthal non-uniformities in temperature profiles around the center plane of both the regenerator and the pulse tube. Inadequate diffusion bonding in the initial aftercooler resulted in non-uniform temperatures in the aftercooler and regenerator warm end where temperatures were as high as 350 K. Jetting into the pulse tube through both the warm and cold heat exchangers also contributed to the poor performance. This paper discusses the performance after an improved aftercooler and pulse tube modifications are added. The steps taken to eliminate the non-uniformities and their effect on the cooler performance are discussed.

Development and experimental investigation of Stirling-type pulse tube refrigerator (PTR) below 20 K; cold compressor and colder expander

“…All the slit-type heat exchangers are designed to have the temperature difference between the working gas and the fin surface not to exceed 1 K at the target heat lift.The tapered multiple-channel slit-type heat exchangers have the following advantages(Ki and Jeong 2012); (i) Smooth flow connection between the converging and the diverging components of the PTR (ii) No thermal contact resistance originated within the heat exchanger body (iii) Geometrically axisymmetric structure with respect to the working gas flow Several researchers have revealed three locations of the PTR that are likely the sources of significant flow mal-distribution; both ends of the pulse tube and the locus between the WHX and the phase controller entrance (this is mainly because of the presence of severe curved flow,thermo-hydraulic gradient, in the radial direction of the PTR components. )(Garaway, Taylor et al 2009, Lewis, Taylor et al 2010, Park, Ko et al 2016. Although the multiple-channel heat exchanger has several advantages as mentioned above, the flow straighteners which consist of a few layers of #200 woven copper mesh (total thickness of 3 mm) are inserted at the connection parts in order to avoid the inherent flow mal-distribution problem(Ki and Jeong 2010).…”