Numerical simulation of nucleate boiling two-phase flow friction pressure drop and heat transfer at different pressure in helically coiled tube

In the nuclear reactor project of Generation III and Generation IV, helically coiled tube steam generators (SGs) are regarded as a primary structure. Through the rationally simplifying helically coiled tube steam generator of the system integrated modular advanced reactor (SMART), the single-tube model of helically coiled steam generator was established. Based on two fluids model and Reynolds stress model (RSM), the flow and heat transfer process in the helically coiled tubes under different pressures for the steam generator was numerically simulated with constant heat flux. In nucleate boiling regine experimental-parameter ranges covered pressures of 2-8 MPa, heat flux of 158.6 kW·m-2·K-1.The numerical results of frictional pressure drop are the closest to Zhao’s correlation, with an average deviation of 25.4%. The outlet quality and the surface heat transfer coefficient increase with increasing pressure. The total pressure drop and the friction pressure drop gradient decrease with increasing pressure. The non-uniform distributions of pressure existed on the cross-section of tube caused by the vapor-water separation phenomenon. It can be described that lower pressure drop in vapor phase and mean while higher pressure in vapor phase. With the increase of the quality, the vapor-phase accumulation zone moves from 90° to 135°. And the buoyancy force and the centrifugal force act together in the two-phase boiling flow. The main influence is the buoyant force under lower quality, and the centrifugal force under higher quality is the main influence.