EXPERIMENTAL AND NUMERICAL STUDY OF NATURAL WATER CONVECTION IN A CLOSED CYLINDRICAL CAVITY

Abstract

The aim of this work is the validation of a computational code developed in OpenFOAM, which will subsequently be used to  simulate the behavior of the prototype employed for Cherenkov radiation detection, located in the Puna Salteña. The need to compare experimental data with numerical results obtained from the computational code motivated the performance of laboratory-scale experiments. The experimental approach consisted of heating water contained in a cylindrical vessel through its lateral walls until a quasi-steady state was reached, and determining the time interval in which the numerical results remain within acceptable relative error margins. Additional experiments involved heating through a constant heat flux applied to the lateral wall, followed by cooling due to ambient temperature. Temperature measurements were recorded during the tests inside the fluid and on the wall of the enclosure. The system configuration consists of a cylindrical glass vessel surrounded by a heater on the side wall, with the top and bottom surfaces thermally insulated. The Rayleigh number range studied is 9.26×10⁶- 2.32×10⁷, Prandtl’s 4.31- 7.37 and the aspect ratio (Height/Radius) of 2.31- 2.58. The simulation was carried out using the BuoyantPimpleFoam transient solver of OpenFOAM v.9, in two dimensions. Three mesh sizes were considered: 30 and 80, 50 and 130, 70 and 180, radial and axial splits, respectively; confirming that the second mesh is capable of generating acceptable results. In addition, the measured data of temperature inside the fluid and the simulated data were compared. The absolute and root mean square errors determined do not exceed 0,5 ºC. Thus, the simulation results obtained under the conditions analyzed are in good agreement with the experimental data for the different test cases, allowing the computational tool to be adjusted for describing the thermal behavior of large water tanks under real meteorological conditions.