Experiments and theory on natural convection heat transfer from bodies of complex shape

Measurements of the heat transfer by natural convection from isothermal bodies to air are reported and compared to the predictions of the method proposed by Raithby and Hollands (1975, 1978). The bodies tested were the cube in various orientations and a body consisting of two touching spheres (a bisphere). The experimental Rayleigh number range extended from 10 to 10 to the 7th. The experimental method incorporated measuring the heat transfer by the transient method and varying the Rayleigh number by varying the pressure. The predictions agreed with the measurements to within an average error of about 3 percent. The results are correlated by single equations, which can be extended to fluids other than air.