In the chemical vapor deposition process of niobium (Nb) coating on fuel particles, the flow rate of the precursor NbCl5 vapor significantly influences the growth and properties of the thin films. However, measuring the vapor flow rate poses challenges due to the strong acidity of NbCl5, rendering the evaporation process a "black box" operation. In this study, a Volume of Fluid (VOF) method is developed to simulate the gas-liquid interface evaporation and wall boiling of NbCl5 in tank evaporator using argon (Ar) as carrier gas. The impact of various operating conditions, including liquid level height, flow rate of Ar carrier gas, and heating temperature, on the two-phase flow and the heat and mass transfer characteristics within the tank evaporator are investigated. Simulation results reveal that liquid level height primarily affects the evaporation area. When the liquid level resides in the near-bottom region of the tank, lowering the liquid level height significantly reduces the evaporation area, resulting in a decreased NbCl5 vapor flow rate at the evaporator outlet. When Ar gas is introduced into the evaporator, two distinct vortex structures are formed: a NbCl5 vapor vortex and an Ar gas vortex. Increasing the Ar gas velocity enables rapid sweeping of NbCl5 vapor from the liquid surface and lowers the saturation vapor temperature at the interface, thereby enhancing the evaporation rate. As the Ar gas velocity increases from 0 m/s to 2.1 m/s, the mass flow rate of NbCl5 vapor rises from 0.047 g/s to 1.095 g/s. Raising the heating temperature increases the liquid temperature at the evaporation interface, accelerating liquid evaporation. As the heating temperature increases from 533 K to 543 K, the NbCl5 vapor mass flow rate increases from 0.280 g/s to 0.359 g/s. These simulation results offer practical guidance for optimizing the operating conditions of the gas-carrying evaporation process and the evaporator structure.