Experimental investigation of natural convection heat transfer in a ship cargo tank filled with high-viscosity fluid

Experimental research was conducted to elucidate heat transfer by natural convection in a ship cargo tank filled with high-viscosity fluid (heavy fuel oil). The cargo tank was modeled as a 1/20 scale rectangular enclosed volume. The fluid in the enclosed volume was heated from the bottom plate by resistance wires and cooled from the top plate using a circulating thermostatic water bath. The isothermal boundary condition was used for the bottom and top plates. All other boundaries of the rectangular enclosed volume were insulated. Glycerin was used as a working fluid in the enclosed volume to model the large temperature-dependent variation in the viscosity of heavy fuel oil. The effects of the temperature difference between the bottom plate (T_H) and top plate (T_C) on the heat transfer by natural convection and the temperature field in the enclosed volume were experimentally investigated. Experiments were conducted for three different temperature differences (ΔT_p = T_H − T_C) and the Rayleigh (Ra) number was varied between 1.43 x 10⁸ and 6.57 x 10⁸. The Prandtl (Pr) number was varied in the range of 1633.9 ≤ Pr ≤ 3612.1. The temperature profiles in the enclosed volume are presented and the mean Nusselt (Nu) values are calculated. The mean Nu value increased as the ΔT_p increased. In contrast, the time required for the system to stabilize is inversely related to the ΔTp value. The natural convection characteristics in a tank filled with high-viscosity fluid were obtained and an experimental correlation between the Nu and Ra numbers was developed.