Study on forced convective heat transfer in curved pipes: (3rd report, theoretical analysis under the condition of uniform wall temperature and practical formulae)

Abstract

In the authors' previous reports, the theoretical and experimental studies on flow and temperature fields in a curved pipe were made under the condition of uniform heat flux. In the former part of the present report, a theoretical analysis is made about temperature field far downstream from the pipe inlet under the condition of uniform wall temperature, following the same procedure as in the previous papers. Nusselt number is found to be remarkably affected by a secondary flow due to curvature. The result shows that in the first-order approximation the Nusselt number of heat transfer in a curved pipe does not differ for uniform wall temperature or uniform heat flux case, in both laminar and turbulent regions. In the latter part, the formulae of Nusselt numbers obtained by the authors' study are arranged so as to have simpler expression for a practical use. It is also investigated what temperature should be chosen in calculation of physical properties when these Nusselt number formulae are used.