Heat transfer enhancement in Rayleigh-Bénard convection of liquids using suspended adiabatic honeycombs

Laminar natural convection of water inside box-shaped enclosures heated at the bottom and cooled at the top, with perfectly insulated sidewalls, is studied numerically with the aim to investigate the enhanced heat transfer effects deriving from the suspension of an adiabatic square honeycomb in the middle of the enclosure so as to leave an upper and a lower clearance allowing for horizontal flows. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. Simulations are performed using the Rayleigh number based on the cavity height, the overall number of cells in the honeycomb, and the ratio between the heights of the honeycomb and the cavity, as controlling parameters, whose effects are thoroughly analyzed and discussed. It is found that the suspension of the honeycomb inside the cavity normally leads to a significant heat transfer enhancement, that reaches a peak at an optimal layout of the honeycomb structure.