Influences of accelerating states on supercritical n-decane heat transfer in a horizontal tube applied for scramjet engine cooling

Supercritical n-decane is applied in the regenerative cooling system of scramjet engines while scramjets are always in various irregular movements. With the desire to explore heat transfer performance of supercritical n-decane under actual flight conditions, numerical simulations and analysis of different states during the accelerated flight process are carried out under three different heat fluxes and eight varying acceleration states. Specific flow and heat transfer mechanisms are explored by analyzing the temperature and flow fields affected by acceleration. Results show that acceleration weakens the intensity of the first abnormal heat transfer state but does not affect its appearance location, and there are almost no effects on the second heat transfer state. Another important conclusion is that the external factors have a great influence on supercritical n-decane heat transfer. The overall average surface heat transfer coefficient could be even up to 27.5% higher than for an ordinary horizontal tube. It is indicated that more attention should be paid to the external factors when investigating supercritical flow and heat transfer in the research and development of scramjet engine cooling.