Experimental investigation of convective heat transfer to supercritical pressure n-decane and RP-3 under trans-critical and cracking states

The increasing demand for higher flight speeds in hypersonic vehicles has catalyzed the advancement of active regenerative cooling technologies based on endothermic hydrocarbon fuels. This work carried out experimental investigation on the convection heat transfer performance of supercritical n-decane and RP-3 within a horizontal GH3128 microtube with 2 mm inner diameter from room temperature to exceeding 50 % cracking conversion rate at 3−6 MPa. The rise rate of fuel temperature along the tube in the cracking reaction zone is lower than that in the inlet, trans-critical and supercritical zone. There exists heat transfer deterioration attribute to the inlet effect and inlet laminar flow in the inlet region, and the subsequent heat transfer enhancement induced by the significant buoyancy effect in the trans-critical region. Lower pressures lead to earlier onset and greater magnitudes of heat transfer enhancement. In the supercritical zone once the fuel temperature surpasses the quasi-critical temperature, no obvious heat transfer anomaly occurs. Upon the onset of the cracking reaction, a slight augment in the convection heat transfer coefficient is obtained, attributed to the increase in the thermal conductivity of the cracking mixture. This work provides valuable support for the thermodynamic design of hypersonic vehicle cooling channels.