Experiments on heat transfer from spheres to liquids have been carried out in the range of 2.0×10^-4<Re<900, 7.0<Pr<2.4×10⁴ and 5.7×10^-3<Gr<10⁷ for combined convection. A sphere, 46.03 mm in diameter, composed of eleven copper segments, and two brass spheres (19.03 and 9.534 mm in diameter) have been used. Test liquids used were 0.96%, 2.59%, 2.62% CMC aqueous sol. and 0.69%, 0.97%, 1.07% MC (methylcellulose) aqueous sol. The experimental data are summarized by the following relation:
Nu_m-2 = [{(126Re+57Re^3/2)Pr^1/3/(1+52Re^1/2+100Re)}^3/2 + (0.44Gr^1/4Pr^1/4)^3/2]^2/3(μ_b/μ_s)^1/4 where μ_b is the viscosity at the bulk liquid temperature t_b and μ_s is the viscosity at the sphere surface temperature t_s. This equation has been shown to represent measured values of Nu_m within an average deviation of 13.6 per cent.