Numerical study on heat transfer deterioration of n-decane during pyrolysis under supercritical pressure in a vertical tube

Abstract

For accelerating hypersonic vehicles, it is important to understand the effects of various factors on heat transfer deterioration. The heat transfer characteristics of supercritical n-decane with pyrolysis were numerically simulated inside a vertical tube. The effects of flow direction, mass flow rate, heat flux, inlet temperature, and flight acceleration on the heat transfer characteristics were investigated. When the inlet temperature was relatively low or the fluid was decelerated vertically upward, a typical M-shaped velocity distribution was formed, indicating the heat transfer deterioration (HTD). Furthermore, the decrease in wall heat flux, as well as the increase in mass flow rate, inlet temperature and flight acceleration in the same direction as the flow makes the HTD gradually disappear. Finally, a new relationship was established between the heat flux and the flight acceleration and inlet temperature to determine critical heat flux under which HTD developed in the upward flow.