An Experimental Study of the Gas-Liquid Mass Transfer in the Volume Control Tank

The Volume Control Tank (VCT) is an important equipment in pressurized water reactor nuclear power plant (NPP). The nitrogen in the upper part of the VCT will enter the primary loop system through gas-liquid mass transfer. It will produce radionuclide ¹⁴C and affects flow and heat exchange stability. Gas-liquid mass transfer under submerged jets in VCT has rarely been studied. In this paper, an experimental study was carried out to investigate the gas-liquid mass transfer in the VCT with a submerged jet flow. The experiment was carried out in a wide range of the Reynolds number (Re) and Schmidt number (Sc) (1.3 × 10⁵ < Re < 2.5 × 10⁶, 135 < Sc < 580). The empirical correlation of the Sherwood number (Sh) was given with a maximum error of 14.1%. The effects of the geometry (jet diameter, jet height), thermal and hydraulics parameters (temperature, operating pressure, inflow flow rate) on the interface mass transfer process in the VCT were discussed. The result shows that with the increase of inflow flow rate, the mass transfer coefficient (K_L) and mass transfer flux (N_i) increase. The increase in temperature causes an increase in K_L, but has no obvious effect on N_i. With the increase of the operating pressure, N_i rises. But K_L is rarely changed. And the decrease of the inlet pipe diameter has a positive effect on K_L and N_i. Furthermore, it was found that K_L is proportional to inflow flow rate and D_AB^0.52 (D_AB is the diffusion coefficient of gases).