Dynamic heat transport and turbulence characteristics of supercritical LNG in a teardrop-structured PCHE under oceanic motion conditions
Jie Sun, Gongnan Xie, Dan Zhao
Abstract
Our study investigates two common complex oceanic motions—rolling plus heaving and pitching plus heaving—and their effects on supercritical LNG flow within a teardrop-configured printed circuit heat exchanger featuring dimples and protrusions. Inertial forces arising from rotational and translational motions are incorporated into the Navier-Stokes equations via user-defined functions to simulate realistic ocean conditions. Comprehensive statistical analyses of transient and time-averaged physical parameters reveal insights into thermal transfer efficiency under these dynamic conditions. Key metrics examined include turbulent heat flux, Nusselt number, Prandtl number, Fanning friction coefficient, pressure drop, turbulent kinetic energy, entropy generation, and the field synergy angle, from perspectives of heat transfer, turbulence, and thermodynamic irreversibility. Results show that rolling plus heaving induces more intense fluctuations in turbulent heat flux and accelerates thermal diffusion compared to pitching plus heaving. Conversely, the lower fluctuation of the Fanning friction coefficient in pitching plus heaving reduces flow-induced pressure losses. The rolling plus heaving mode enhances shear, mixing, and friction effects, with heat transfer dominated by convection, whereas the pitching plus heaving mode exhibits alternating convection and conduction. Irreversible energy losses are primarily driven by temperature gradients under both motions. Teardrop dimples generate larger heat transfer entropy than teardrop protrusions, while the opposite trend is observed for viscous dissipation entropy. Evaluations of heat exchange efficiency and flow resistance indicate that teardrop dimples outperform protrusions, with integrated performance indices ranging from 1.02 to 1.08 under rolling plus heaving and 1.04 to 1.06 under pitching plus heaving motions.