[en] The KNGR(Korea Next Generation Reactor) adopted DVI(Direct Vessel Injection) system instead of conventional cold leg injection system. In this paper, time and velocity reduced linear scaling law is suggested to be used in the prediction of ECC direct bypass flow rate during LBLOCA reflood phase. The new scaling law is derived from 2-dimensional 2-fluid momentum equations. The velocity is nondimensionalized by Wallis dimensionless parameters. The newly developed scaling law is appropriate to be used in the prediction of multi-dimensional thermal hydraulic phenomena such as in the downcomer during LBLOCA reflood phase because the aspect ratio is preserved as in the prototype