Study of forced convective heat transfer in curved pipes (2nd report, turbulent region)

Abstract For this paper the effect of curvature on heat transfer for fully developed turbulent flow in curved pipes on the condition of constant heat flux was studied theoretically and experimentally. In the analysis, a boundary layer is considered to exist along the pipe wall. Local shear stress and local heat flux at the wall are given on the basis of reducing the resistance ( λ s ) and the Nusselt number ( Nu s ) formula for straight pipes to the local relation of friction and heat transfer. When the formulae for straight pipes are given as λ s ∞ Re −1/ m and Nu s ∞ Re ( m −1)/ m , it is shown that the dynamic similarity and also the similarity for heat transfer in curved pipes depend upon Re ( a / R ) m /2 . The resistance coefficient and the Nusselt number for curved pipes are obtained by putting m = 4 or m = 5. The Nusselt numbers obtained from measurement of the velocity and temperature distribution in the air flow through the curved pipes of R / a = 40 and 18·7 are in good agreement with the theoretical results.