Heat transfer enhancement in a cubical enclosure with hot and cold sectors in two opposite vertical walls

Abstract

The natural convection of air in a cubical enclosure with hot and cold sectors in two opposite vertical walls is numerically investigated. Although this case is interesting for possible heat transfer enhancement and flow pattern control, it has not been described previously in literature. Final steady states exist over the whole Rayleigh number range investigated (103 - 108). The flow has a rotating flow structure, with rotation axis perpendicular to the one for DHCC, and with marked temperature stratification in the central core. An increase in heat transfer with respect to the conventional, differentially heated cubical cavity (DHCC) is found. Heat transfer is remarkably enhanced at Rayleigh numbers of 106 or less, in which conduction through the fluid near the active walls plays a major role. However, in the convective regime at high Ra heat transfer is only marginally higher than in the DHCC. This behaviour is physically explained and an expression for overall Nusselt number is proposed.