Cryogenic spill thermal loading in a 9% Ni steel LNG tank

A common cryogenic-spill simplification is to prescribe a low temperature directly to the exposed region. That approach is efficient, but it does not reproduce the time-dependent cooling process governed by boiling heat transfer.

Cryogenic exposure is often reduced to a prescribed cold temperature, but actual LNG/LN₂ contact produces a time-dependent heat-transfer process controlled by boiling regime, surface temperature, exposure duration and local restraint. Minimum temperature alone does not define the structural demand.

The study compares a steady-state prescribed-temperature method with a transient film-condition method derived from LN₂ boiling heat-transfer behavior. Both methods are applied to the same shell-based 9% Ni LNG tank geometry, material model, mesh, support condition, gravity preload and exposure region.

The case compares steady-state prescribed-temperature loading against transient film-condition thermal loading derived from LN₂ boiling heat-transfer behaviour. The resulting temperature histories are used to evaluate progressive cooling, hot–cold transition gradients and time-dependent stress development in the tank shell.

Temperature histories, shell-surface temperature variation, von Mises stress contours and stress-time histories are compared to show how thermal-boundary formulation changes predicted stress development.

Outputs include temperature-time histories, spatial temperature gradients, von Mises stress contours, stress histories at transition-region nodes and comparison between immediate cold-state response and physically progressive cooling response.

The case demonstrates that the hot–cold transition region can govern thermal stress and that cooling history may be necessary for physically representative LNG tank-shell assessment.

For LNG-related structures, the case demonstrates that thermal boundary formulation is an engineering decision, not a modelling detail. It helps clients understand when a rapid screening method is acceptable and when transient thermal loading is required for a more defensible structural-integrity interpretation.