Heat transfer in laminar pulsatile flow in a pipe

摘要

Using velocity profiles given by Uchida for a fully-developed, laminar, pulsatile flow in a pipe, the heat transfer in a laminar pipe flow is studied numerically by using the finite difference method. The temperature profile is assumed to besimilar in form to Uchida's velocity profile at the entrance of a heated section of the pipe. The energy equation is then solved to obtain spatial and axial temperature distributions downstream and heat transfer is calculated for a case of constant walltemperature.The spatial temperature profile in pulsatile flow is found to be quite different from that in a steady flow. A thick oscillating buffer region exists which plays an important role in transporting thermal energy from the center core region to theconduction sub-layer which exists next to the pipe wall. The oscillatory temperature profiles along the axial direction are similar except that their amplitudes decrease towards downstream, and finally ceases to exist. The thermal boundary layers exist at all time and become thinner as the oscillatory frequency of the flow increases, which lead to better heat transfer. This enhancement is larger in the entrance region of the heated section of the pipe and rapidly diminishes as flow moves down-stream.