Supercritical carbon dioxide in an array of micro impinging jets

Heat transfer of micro multi-jet with supercritical carbon dioxide is experimentally studied. A thermal micro specimen chip constituting of a concentric distribution of three resistance temperature detectors (RTDs) on a serpentine heater, which was mechanically supported by a 500 mu m thick fused silica sub-strate, was microfabricated and used to obtain the heat transfer coefficient under a range of operating conditions. The jets issued from a concentric array of thirteen micro jets with an interject spacing (S/d) of similar to 1.5, each measuring empty set 205 mu m, which were perpendicularly positioned over the temperature sensors with a relative standoff, L/d, of 7.3. The effect of radial position, heat flux, mass flux and inlet pressure on the heat transfer were studied at an inlet temperature of 21.7 degrees C.Results showed a uniform heat transfer coefficient over the heater with optimum values recorded mostly around the pseudocritical condition. In addition, the heat transfer coefficient increased with pres-sure above the critical condition, which was tied to a corresponding increase in the pseudocritical tem-perature. Furthermore, the observed heat transfer characteristics of the micro jet impingement cooling using multi-jet were compared to single jet under the same working conditions. This comparison showed that although the multi-jet ensued a more uniform temperature distribution over the heater, the single jet performed better due to an undermined heat transfer process in the multi-jet - a consequence of the jet-to-jet interaction.(c) 2022 Published by Elsevier Ltd.