Heat Transfer of Melting Nonadecane Spheres in Natural Convection of Water

This paper deals with experimental and analytical heat transfer study of nonadecane spheres melting in natural convection of water. Experimental local and average heat transfer coefficients were obtained by analyzing photo images of the shape transformation of the nonadecane spheres. The relevant dimensionless parameters were varied in the ranges of 1.8×10⁷ ≤ Gr_n·Pr_n ≤ 1.8×10⁸ and 0.04 ≤ C_nΔT/L_n ≤ 0.16. We found that (1) the melting nonadecane sphere was covered with thin nonadecane liquid film flowing upwards along the sphere to make a liquid cap on the top. The cap regularly repeated formation and splitting off, (2) on the lower hemisphere the experimental local heat transfer coefficients were slightly higher than the analytical ones and on the upper hemisphere the experimental local heat transfer coefficients were slightly lower than the analytical ones, and (3) the experimental average Nusselt number was correlated by Nu = 0.151 (Gr_n·Pr_n)^0.257(C_nΔT/L_n)^0.117 that was in good agreement with the theoretical one.