Numerical study on the effect of pipe wall heat storage on density wave instability of supercritical water

A time-domain model is developed to study density wave oscillation (DWO) of supercritical flow. The model takes the wall heat storage process into account by introducing a wall metal heat storage equation and a convective heat transfer equation. The present model is compared with the similar studies from the previous literature. After that, the model is employed to study the effect of structural parameters (pipe length, wall thickness, etc.) on DWO of supercritical flow in a heated pipe. The results show that the wall heat storage significantly changes the influence rules of pipe structural parameters on flow instability. Under the situation without the wall heat storage (the wall thickness is zero), system stability first decreases with the pipe length and then tends to be unchanged. While for the case of the wall thickness beyond zero and the wall heat storage should be considered, the variation of the system stability with pipe length is different, and there exists a critical value about pipe length ('Lcr') where the variation of system stability with pipe length is reversed. When pipe length is less than Lcr, the system stability decreases with the pipe length. When pipe length is greater than Lcr, the system stability increases with the pipe length. Moreover, Lcr decreases with the wall thickness.