Secondary Flow Effect on Supercritical Kerosene Oxidation Deposition and Heat Transfer in a Coiled Tube

Deposition in fuel cooling systems remains a challenge to the development of active cooling technologies for air-breathing engines. We experimentally and numerically investigated the influence of the secondary flow and heat-transfer characteristics of supercritical kerosene in a coiled tube on oxidation deposition. A coiled heated tube reactor (3000 mm long, 23 cycles) under constant heat flux and flow rate was applied to simulate the conditions of the fuel side in the heat exchanger of an aero-engine cooling system. The coupling characteristics of coking distribution with the development of secondary flow were studied along the whole pipe. The dynamic pressure, temperature, and velocity were analyzed in two specific circular cross sections located in the bend of the tube. The secondary flows induced in the coiled tube greatly enhance the heat transfer and slightly decrease the deposition rate, resulting in linear wall temperature profiles and a uniform coking distribution along the tube compared to the long straight tube. There is no obvious heat-transfer enhancement or deterioration in the whole coiled tube. The modified heat-transfer correlation of the supercritical RP-3 in the coiled tube was fitted at different flow rates and heat fluxes with an error of ±10%.