Heat transport at boiling, near-critical conditions

Two-phase flow and near-critical phenomena are likely to enhance energy transport in high-temperature hydrothermal systems. We present a series of two-dimensional simulations of two-phase flow of pure water at near-critical conditions. The results show that at near-critical conditions, two-phase convection can be more efficient in transporting energy than single-phase convection. The highest heat fluxes are attained when two-phase heat-pipes form near the bottom boundary, recharging the root of the upflow zone and thereby enabling the formation of broad upflow regions. When the system becomes more vapor-dominated, it loses this ability, upflow zones become narrower and the energy efficiency drops to more moderate values.