Experimental investigation of free convection from short horizontal cylinder to Newtonian and power-law liquids of large Prandtl numbers

The results indicated that Newtonian fluids attain higher free convection heat transfer coefficient than the power-law fluids by 16% or more. Nusselt number (Nu = hd/k) of the laminar free convection data is correlated in terms of the power-law index and in classical and non-classical forms. Correlations cover Grashof number (Gr∗ = gβqd4/kυ2) from 33 to 1.68 × 107, Rayleigh number (Ra∗ = gβqd4/kυα) from 6.1 × 104 to 6.88 × 108, Prandtl numbers (Pr = cpμ/k) from 30 to 1850, Prandtl numbers ratio (Prb/Prw) from 1.03 to 133 and heat generation parameter from 0.001 to 0.009. The developed non-classical correlation that is based on the presented experimental data is the first correlation to consider the heat generation parameter. It predicts the experimental Nu within ±5% whereas the classical form correlation predicts Nu with uncertainty over ±20%.