Free-convection heat transfer coefficients along a vertical surface with square protrusions

The effect of repeated horizontal protrusions on the free-convection heat transfer from a vertical, isothermal surface has been experimentally investigated. The protrusions have a square section and are made of a low thermal conductivity material. Experiments were conducted by varying the number of the protrusions over the surface (whose height was held fixed). The local heat transfer coefficient was obtained by means of the schlieren optical technique. The protrusions were found to significantly alter the heat transfer distribution along the surface, especially in the vicinity of each obstacle. For the range of parameters here considered, the addition of low-conductivity protrusions lead to a decrease in the convective heat transfer rate from the vertical surface in the 0-10% range.