Enhanced heat transport by turbulent two-phase Rayleigh-Bénard convection

Abstract

We report measurements of turbulent heat-transport in samples of ethane (C$_2$H$_6$) heated from below while the applied temperature difference $ΔT$ straddled the liquid-vapor co-existance curve $T_ϕ(P)$. When the sample top temperature $T_t$ decreased below $T_ϕ$, droplet condensation occurred and the latent heat of vaporization $H$ provided an additional heat-transport mechanism.The effective conductivity $λ_{eff}$ increased linearly with decreasing $T_t$, and reached a maximum value $λ_{eff}^*$ that was an order of magnitude larger than the single-phase $λ_{eff}$. As $P$ approached the critical pressure, $λ_{eff}^*$ increased dramatically even though $H$ vanished. We attribute this phenomenon to an enhanced droplet-nucleation rate as the critical point is approached.

4 gages, 6 figures