Effects of variable heat flux at supercritical pressure in vertical pipe flow

•High-fidelity numerical simulation is employed to examine the role of non-uniform heat ux at supercritical pressure.•Axially varying heat ux results in the peak and valley in the wall temperature, indicating a possible heat transfer deterioration control approach.•Thermal stratification was observed in a case with circumferentially-varying heat ux in vertical pipe ow.•Thermal stratification brought the secondary ow along with asymmetric profiles of mean ow parameters. It is a well-established fact that the heat transfer at supercritical pressure is complex and several numerical investigations have been conducted to address this issue. However, the focus of such studies remains uniform heat flux. Therefore, here we report the outcomes of direct numerical simulations performed with different profiles of non-uniform heat flux for supercritical carbon dioxide. Flow in a small pipe with a diameter of 2 mm is considered and vertical orientation with upward direction of fluid flow was chosen. The heat flux was varied in the axial and circumferential direction of the pipe. The circumferential heat flux induces the thermal stratification which resulted in a higher wall temperature at one side where heat flux was maximum. While axially varying wall heat flux results in the peak and valley in the wall temperature. The study also suggests that axially varying heat flux can be a possible strategy to control the heat transfer deterioration.