The effect of heat storage on supercritical flow stability in two heated parallel channels

•First successful study of supercritical instability including wall thermal energy storage effects which is in good agreement with experiments.•Detailed analysis of wall heat on parallel channel topology.•Precise predictions of period of oscillation with and without inclusion of wall.•1D-Linear, frequency domain model. One-dimensional (1-D) numerical simulations were carried out of two vertical heated parallel- channel experiments using a linear frequency domain approach to investigate the wall energy storage effect on the system's stability boundary for supercritical water up-flow. Oscillatory instability boundaries of the experimental cases with two different wall thicknesses, uniform and non-uniform power distributions are produced, assessed and discussed. In all, 31 cases were examined. These instability predictions with wall energy storage effects are compared with experimental data and other numerical results obtained without wall heat effects. There is improved agreement on the stability boundary predictions when the wall energy storage effect is included; however, all results fall within the experimental uncertainty. There is a cancellation effect of the wall energy storage in two parallel channels compared to a single channel. Consequently, the effect of wall energy storage is relatively small for the experiments modeled.