Numerical study on the thermal hydraulic characteristics of ERVC system

Under the serious accident of core melting, in-vessel retention (IVR) can end the accident process inside the pressure vessel as an emergency strategy. The ERVC can remove the residual heat of the core. The paper utilizes the method of enhanced heat transfer to improve CHF threshold. In this paper, according to investigating the types of fins, three fin structures (Longitudinal fin, Rectangular fin, Cylindrical fins) are selected and placed on the thermal insulation layer, which change the internal structure of the flow channel to play the role of turbulence disturbance. For the multi-phase flow model, a boiling model (RPI model) is used, considering the momentum exchange between the two phases, like drag force, virtual mass force, and wall lubrication force, as well as interphase mass transfer and heat transfer. The mathematical physical model is verified for the slicing experiment of ULPU, and the calculated result is compared with experimental physical values, as well as the error is within acceptable ranges, which are in good agreement. The calculations show that the CHF effect of cylindrical fin is better than rectangular fin and longitudinal fin, since that the turbulence intensity of around cylindrical fin is stronger than rectangular fin and longitudinal fin. For the same fin, when the fins spacing are smaller and fins height are between 40-60 mm, the cylindrical fin geometry has better cooling effect on the core and the residual heat removing. The enhanced heat transfer effect of cylindrical fins can be improved by 21 %. The numerical simulation calculation results can provide certain reference for engineering design.