Numerical simulation of transitional flow and heat transfer in a smooth pipe

A two-dimensional boundary-layer program STAN5 is modified to incorporate a low-Reynolds number version of the K-ε, two-equation turbulence model to simulate automatically the laminar, transitional and turbulent flow zones and also the onset of transition and to account for the influence of inlet turbulence intensity upon the flow and heat transfer in a smooth pipe. The prediction for Reynolds number ranging from about 1000 to 10000 is made under inlet turbulence intensity ranging from 0.1 to 8.0%. Results show that when Re < 2068 and Re > 4809, inlet turbulence intensities have no influence upon flow and heat transfer but when 2068 ≤ Re ≤ 4809, the influence is rather strong, and when the inlet turbulence intensity is 1.0%, the predicted relation between average Nusselt number and Reynolds number is in good agreement with the experimental correlation. In the fully developed region, flow and heat transfer are not affected by inlet turbulence intensities, and the agreement between the results and data for the friction coefficient is good.