CFD analysis of induced vibrational effects on unsteady natural convection in a cylindrical cryogenic storage tank

Cryogenic storage of liquefied gases, particularly LNG in petroleum engineering, depends on stable natural convection to regulate heat transfer and thus minimize boil-off losses. However, this internal convection can itself be influenced by naturally induced environmental vibrations. Therefore, the present paper aims to investigate the effect of a vertically induced vibration on the thermo-hydrodynamic characteristics as well as on the evaporation rate during the cryogenic storage of a liquified gas with Pr = 2 in a cylindrical tank. Under axisymmetry assumption, the tank has been modeled in a rectangular cavity, where the bottom is thermally insulated; however, external heat leaks occurs through the sidewall and the evaporation free surface. Based on a dimensionless CFD formulation, the effects of vibration amplitude, represented by the vibrational Rayleigh number (103 ≤ Raω ≤ 105), as well as the vibration angular frequency (101 ≤ Ω ≤ 103), have been highlighted. In addition, the external heat leaks and the heat flux due to surface evaporation have been quantified using the Nusselt number. Based on a finite element method simulation, the numerical results showed that that vertical vibrations interact with the buoyancy force induced by gravity, generating a pulsating volumetric force that produces a synchronous periodic response in the evaporation rate. In addition, increasing the vibration amplitude periodically enhances both the evaporation rate and the convective heat transfer, reaching up to 40% compared to the stationary state when the vibrational acceleration is equivalent to the gravitational force (Ra = Raω). Moreover, moderate vibration frequencies (around Ω = 102) further maximize these effects, however, very high frequencies tend to stabilize the evaporation rate and heat transfer toward the stationary values, partially counteracting the influence of amplitude.