Experimental assessment of the thermal-hydraulic performance of packed-sphere oscillating-flow regenerators using water

Regenerators are storage-type heat exchangers with a wide-range application in thermal systems. In refrigeration, they can be used as passive thermal storage devices in Stirling and pulse-tube coolers, or as active magnetocaloric regenerators in magnetic refrigerators. In either case, the performance of the cooling system is significantly influenced by the regenerator thermal effectiveness and by viscous losses. A laboratory apparatus for testing passive regenerators that uses water as the thermal fluid was developed aiming at quantifying the fluid pumping power and the regenerator heat transfer effectiveness as a function of operating parameters such as frequency and thermal capacity ratio (utilization factor) for different regenerative materials and packing geometries. In the present paper, the experimental rig, data processing and test results obtained for packed beds of stainless steel, lead and gadolinium spheres with different particle diameters are described and discussed.