Experimental analysis of cooling and heating performance of serial and parallel connected counter-flow Ranquee–Hilsch vortex tube systems using carbon dioxide as a working fluid

•The highest ΔT was highest as 76.9 K in parallel connected RHVT system.•The most efficient case in this study brass-six nozzle at 550 kPa.•CO2 provides higher thermal separation than air. This study examines the performance analysis of two counter flow Ranquee–Hilsch Vortex Tubes (RHVT) having the same geometrical properties in the condition of serial and parallel connection. The performance of CO2 as a working fluid in the vortex tube by using nozzles having 2,4 and 6 orifices, which were manufactured from polyamide and brass material has been experimentally investigated. Experimental studies were carried out by compressing CO2 through the compressor to the vortex tube at pressures between 150 and 550 kPa. The most important physical property of a RHVT is the ratio of L/D which is equal to 14 in this study. In addition, by using the data obtained from experimental results, the second law efficiency was calculated for different working conditions of the systems by exergy analysis. The highest overall temperature difference (ΔT) was obtained as 76.9 K when using parallel connected RHVT system with brass-six nozzle.