Flow dynamics in transient heat transfer of n-decane at supercritical pressure

Turbulent heat transfer of hydrocarbon fuel at supercritical pressure plays a crucial role in regenerative cooling of aerospace propulsion systems. In this paper, flow dynamics in transient heat transfer of n-decane at a supercritical pressure of 5 MPa has been numerically investigated, focusing on the effects of a number of key influential parameters, including the surface heat flux, surface heating rate, cooling tube length, and inlet flow velocity, on the transient responding behaviors. Results indicate that the transient responding process is dictated by two fundamental mechanisms: the initial thermoacoustic oscillation, which is caused by strong fluid thermal expansion, and the subsequent transient convection. The thermoacoustic oscillating magnitude increases as the surface heat flux, surface heating rate, and cooling tube length are increased, but it decreases as the inlet flow velocity is increased. The surface heating rate and cooling tube length also exert strong impacts on the oscillating frequency of the thermoacoustic wave. Moreover, the cooling tube length and inlet flow velocity significantly affect the second-stage transient convective process and thus the total transient responding time, which both increase as the cooling tube length is increased and/or the inlet flow velocity is decreased. Results obtained herein are helpful for fundamental understanding of the transient heat transfer mechanisms relevant to regenerative engine cooling processes.