Abstract: The objective of the present paper is to study experimentally the heat transfer to non-Newtonian power-law fluid falling films flowing down the outside surface of a vertical stainless steel tube which has 20mm in outside diameter, 1mm in thickness, and 1100mm in length. The test liquid is an aqueous solution of carboxymethycellulose sodium(CMC solution) with the concentration of 8000×10^-6 (mass ratio). Rheological parameters of the solution were measured by the NXS -11 rotational viscosimeter within t=15~85℃ and empirical formulae for the variation of the parameters with solution temperatures are given as follows:n=0.644+0.245×10^-2 t, K=1.365exp(-0.0305 t), where n is the flow behavior index and K is the consistency coefficient. Based on a simplified physical model, the correlation of the average Nusselt number as a function of the modified Reynolds number and the modified Prandtl number can be obtained by fitting the test data. The correlation is given as follows:Nu_pl=2.0 Re_pl^0.395 Pr_pl^1/3.

Key words: non-Newtonian fluid, thin film flow, heat transfer