Chemical Engineering Science, Vol.52, No.19, 3265-3275, 1997
Effects of an Oscillating Interface on Heat-Transfer
The effects of gas/liquid interfacial movement on heat transfer from a discrete heat source on a vertical wall to the liquid were investigated experimentally for two situations of interfacial oscillations using air-water systems : air/water interfacial oscillation of an oscillating water column and air/water interfacial wave in a water tank. Experiments on the oscillating water column have shown that the heat transfer near the air/water interface is strongly affected by the oscillating interface. The local heat transfer coefficient near the interface increases rapidly with the oscillation frequency compared to the heat transfer measured at a point totally submerged in the liquid but remote from the interface. The local heat transfer near an oscillating interface can be related to the periodic renewal of the boundary layer with the fresh bulk liquid. The influence due to the interfacial movement gradually diminishes towards a distance approximately twice the oscillation amplitude measured from the equilibrium gas/liquid interfacial position. It has also been found that the Nusselt number and the oscillatory Reynolds number correlate the heat transfer data reasonably well. Experimental results obtained using air/water interfacial waves have shown that the local heat transfer rate is similar to those obtained using the oscillating water column under the conditions of similar wave frequency and amplitude.