Performance of supercritical carbon dioxide heat transfer in several enhanced tubes under external high-temperature airflow

Abstract

A precooler is installed in the Synergetic Air-Breathing Rocket Engine to ensure the compressor operates properly at high Mach numbers. To better fit the actual precooler scenario, the present study simulated the flow and heat transfer fields of supercritical carbon dioxide (sCO2) in a horizontal tube in which hot air counterflows outside. In the coolant channel, two types of ribs were selected and added, including rectangular ribs as well as isosceles triangular ribs. The geometry parameters of the rib and its configuration on the flow and heat transfer characteristics of sCO2 were examined in detail. Results show that six out of eight cases revealed an increase in Nut over 100% in the triangular rib, making it the optimal enhanced structure. Compared to rectangular ribbed tubes, triangular ribbed tubes display a different variation trend in Nut with rib height due to the combined effects of fluid disturbance and recirculation zone. Both types of ribs increase their Nut first and then decrease it with the rise of rib pitch, which may be due to the fact that high turbulence zones require several distances to develop. This research can provide theoretical foundations and data support for the design of high-efficiency air-precoolers in the future.