ABSTRAKT

The effect of pulsating frequency on heat transfer from a rectangular flat plate in laminar pulsating flows inside a vertical circular channel was studied numerically to explore the controlling mechanism for heat transfer enhancement. Quantitatively accurate, second-order schemes for time, space, momentum, and energy were employed, and fine meshes were used. The unsteady, incompressible Navier−Stokes equations along with the energy equation were solved by the ANSYS^® 13.0 segregated solver. The numerical results agreed well with the data from the experiment. It is found that the spatial averaged surface temperature of the rectangular flat plate fluctuates with time, and the temperature field around the rectangular flat plate oscillates in special modes at the same frequency as the flow pulsations. The heat resistance was observed to be larger during flow reversal than that during forward flowing, and it fluctuates in phase with the pressure waves. In addition, a detailed analysis found that the RMS (root-mean-square) value of the axial velocity controls the heat transfer enhancement in pulsating flows at different pulsating frequencies when the pressure amplitude and the Reynolds number remain unchanged.