Characteristics and Critical Criteria for Unstable Flow and Heat Transfer of RP-3 Aviation Kerosene in a Vertical Upward Channel

Aiming at the cooling heat transfer problem of air-kerosene heat exchanger, an experimental research on unstable flow and heat transfer of supercritical-pressure RP-3 aviation kerosene in a vertical upward round tube has been performed. The transition process from stable flow to unstable flow heat transfer was studied. The oscillation characteristics and mechanisms of measured parameters were investigated. Effects of the mass flux, inlet fluid pressure and inlet fluid temperature on wall temperature oscillation and unstable boundary were analyzed. Two dimensionless parameters were proposed, and the prediction criteria for unstable boundary was developed. The results show that when the high heat flux is imposed on the channel, the dynamic response process of boundary layer to heat flux transits to the unstable oscillation, resulting in the unstable flow and heat transfer problems. The density gradient in the boundary layer becomes smaller with the increasing pressure, and the stability of boundary layer to high heat flux is improved, thus the critical heat flux for unstable flow and heat transfer is increased. The proposed prediction criteria can reasonably predict the critical heat flux of unstable flow and heat transfer, and meets the engineering application of air-kerosene heat exchanger design. © 2022, Science Press. All right reserved.