Experimental study on thermal stratification in water pool with vertical heat source

•Heating experiments were conducted using a small pool test apparatus to investigate thermal stratification in a water pool with a vertical heat source.•Spatial distributions of temperature and velocity in thermal stratification in the small pool were measured using thermography and PIV and analyzed to characterize their spatial distributions.•The mesh size of CFD simulations must be sufficiently small to resolve the flow structure of internal convection, including the thermal stratification boundary. Thermal stratification is a common phenomenon observed in various systems, including bathtubs, lakes, and pools in nuclear facilities. It is considered system-dependent; thus, its occurrence in different systems must be investigated. In this study, heating experiments were performed in a two-dimensional water pool to investigate the thermal stratification mechanism where a source is immersed in a pool, as in spent fuel pools in nuclear power plants. In addition to temperature measurements using thermocouples, the spatial structure of thermal stratification was obtained by visualizing the temperature and velocity fields using thermography and particle image velocimetry (PIV). Computational fluid dynamics (CFD) simulations were also performed as a benchmark analysis using the experimental data, and the simulated and experimental results are in good agreement.