Numerical investigation of fluid flow and heat transfer of oscillating pipe flows

The RANS method with Saffman's turbulence model was employed to solve the time-dependent turbulent Navier-Stokes and energy equations for oscillating pipe flows. The method of partial sums of Fourier series was used to analyze the harmonic velocity and temperature results. The complete structures of the oscillating pipe flows and the averaged Nusselt numbers on the tube wall were provided by numerical simulations over wide ranges of the Reynolds number and the Keulegan-Carpenter number. Present numerical results were validated by comparing the laminar flow results to analytic solutions and turbulence flow results to published experimental data. The effects of the governing parameters on the velocity, temperature, and Nusselt number distributions are discussed. The enhancement of the heat transfer due to oscillating flows has also been presented. The optimal ratio of the tube diameter over the oscillation amplitude was obtained based on the existence of a nearly constant optimal Keulegan-Carpenter number. The potential application of the present results in sea water cooling is also discussed.