Local friction and heat transfer behavior of water in a turbulent pipe flow with a large heat flux at the wall

摘要

The present study investigated the behavior of friction and heat transfer coefficients of water flowing turbulently in a relatively long (i.e., 950 diameter long) circular pipe. When a large heat flux was applied at the wall, the viscosity ofwater significantly decreased along the axial direction due to the increasing temperature of water. A concept of a "redeveloping region" was introduced, where the local heat transfer coefficient increased while the local friction coefficient decreased due to the above-mentioned viscosity change. The present study proposed the use of local bulk-mean temperature to determine local Nusselt numbers by using local Reynolds (Re{sub}(LB)) and Prandtl numbers (Pr{sub}(LB)), a method that automatically took intoaccount the effect of axial viscosity change on the evaluation of local heat transfer coefficients. A new turbulent heat transfer correlation for the prediction of the local Nusselt number is given as Nu{sub}x = 0.00425Re{sub}(LB){sup}0.979·Pr{sub}(LB){sup}0.4·(μ{sub}w/μ{sub}b){sup}-0.11