Flow and Heat Transfer Characteristics of Supercritical N-Decane in Adjacent Cooling Channels with Opposite Flow Directions

To ensure the safety of a scramjet, an arrangement scheme of adjacent regenerative cooling channels with opposite flow directions is adopted to decrease the maximum wall temperature. Based on extended corresponding-state methods, the flow and heat transfer characteristics of supercritical n-decane in cooling channels with same and opposite flow directions under a pressure of 3 MPa are comprehensively investigated in this paper. Compared to adjacent cooling channels with same flow direction, the local maximum wall temperature in adjacent cooling channels with opposite directions is notably reduced. Moreover, the effects of the heat flux and gravity on the development of flow field are analysed. A pair of recirculation zones is found close to the bottom wall of the cooling channels along the flow direction, the scale of which greatly expands with increasing heat flux. Once the heat flux density reaches a critical value, a phenomenon of flow asymmetry occurs. In addition, the small recirculation zones induced by the buoyancy force narrow when the gravity and heat flux directions remain the same, and the gravity effect could inhibit the generation of small-scale vortices and flow asymmetry.