Non-monotonic Ice-core Thawing in Water Pool

This study demonstrates a non-monotonic dependence between pool temperature and thawing time for the ice-core thawing problem. Numerical simulations reveal that this anomaly arises from competing convective mechanisms driven by the density-temperature singularity at ~4°C of water. The sides come from the singularity chaotic flow induced by boundary-core thermal gradients, and the normal natural convection stabilized by buoyancy from the density extremum near the core. Pool size modulates the competition between chaotic flow and natural convection by the Rayleigh numbers, which govern both the extreme points in thawing time and the range of the non-monotonic effect, enabling precise control over thawing kinetics. A scalable energy-based lumped-parameter theoretical model, incorporating a Rayleigh-dependent effective thermal conductivity, is proposed to capture the non-monotonic trend qualitatively. The insights elucidate the role of non-Oberbeck-Boussinesq effect in ice-core thawing dynamics and advance the design of controlled-thawing technologies for applications such as cryopreservation and organ resuscitation.