External convection coefficients for framed rectangular elements on building facades

Abstract

Using data obtained from a heated test plate fixed to the wall of an eight-storey building, correlations are presented for the external convection coefficient h c, as a function of windspeeds measured at 1 m from the test plate surface and at 11 m above the roof (in the free stream). The effects of a rectangular frame on the value of h c are measured for a range of frame depths, the geometries tested relating to facade configurations which are typical of glazing framework designs commonly found in UK commercial high-rise buildings and atria. For the stated conditions of use, the regression correlations may be used by designers and thermal modellers for the prediction of h c values for a range of typical building facades comprised of mullion and transom-type protrusions. The findings are particularly relevant to improving the accuracy of heat loss calculations from glazing.