Numerical simulation of turbulent flow and heat transfer in multi-channel, narrow-gap fuel element

A computational study of convective heat transfer for turbulent flows in multi-channel, narrow-gap fuel element has been carried out, using a general marching procedure. The fluid distribution adjustment among seven annular-sector channels is based on the assumption of the same pressure drop in these passages. It was found that the inlet velocities of the bilateral channels are lower than those of the middles, and the axial local heat transfer coefficients for the seven channels do not approach the fully developed constant value. At each cross section, the periphery temperature distribution is not uniform, while the local temperature distribution along axial coordinate is of sinuous type with the peak at x = 0.7-0.8 m. At the same Reynolds number, the averaged Nusselt numbers of water in Channel 1 and Channel 7 are higher than those in the middles. The maximum surface temperature increases almost linearly with the inlet water temperature, whereas it decreases almost asymptotically with the inlet average velocity.