TRANSIENT CONJUGATED FORCED-CONVECTION HEAT-TRANSFER WITH FULLY-DEVELOPED LAMINAR-FLOW IN PIPES

This work deals with the problem of transient conjugated forced convec tion heat transfer with fully developed laminar flow in an infinitely long pipe, in which the external surface over a finite length of pipe is subject to a constant wall temperature. The effects are presented o f Peclet number, ratios of pipe radii, wall-to-fluid diffusivity, and conductivity on the interfacial heat flux. The predicted results show that the unsteady heat transfer characteristics depend strongly on the ratios of outside and inside radii, wall-to-fluid conductivity, and t hermal diffusivity. Additionally, the decrease in diffusivity ratio A from 10 to 0.1 results in a longer time for the system to reach the st eady state condition from tau = 6.4 to tau = 265.