关键词: 密度倒置, Taylor-Couette流动, 数值模拟, 传热

Abstract: The thermal convection of cold water has attracted considerable attention due to its relevance to engineering applications, such as the phase change cool storage device. However, the natural convection of cold water in the vertical annulus inherently has a minimum heat transfer rate due to the density inversion phenomenon of water near 4 ℃. It is feasible to reduce the negative effect of density inversion phenomenon on convective heat transfer by imposing a slow axial rotation on the inner cylinder. In order to better understand the heat transfer enhancement induced by the low-speed rotation of inner cylinder, three-dimensional numerical simulation was carried out to investigate the thermal convection of cold water near its density maximum in a finite vertical annulus with a heated rotating inner cylinder over a wide range of Rayleigh and Reynolds numbers (10⁴≤Ra≤10⁶ and Re≤150) for various density inversion parameters. The radius ratio and aspect ratio of the annulus were 0.5 and 8, respectively. Results indicated that the combination of centrifugal and buoyancy forces led to multiple three-dimensional flow patterns in the cold water, which were distinct from the conventional Taylor-Couette flow under the Oberbeck-Boussinesq approximation. Furthermore, the transition of flow regimes in the rotating system was generally beneficial to heat transfer enhancement. However, at relatively high rotation speeds, the increase of Ra could result in the non-monotonic change of the overall heat transfer rate.

Key words: density inversion, Taylor-Couette flow, numerical simulation, heat transfer