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 investigat ed experimentally for two situations of interfacial oscillations using air-water systems: air/water interfacial oscillation of an oscillatin g water column and air/water interfacial wave in a water tank. Experim ents 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 incr eases rapidly with the oscillation frequency compared to the heat tran sfer measured at a point totally submerged in the liquid but remote fr om the interface. The local heat transfer near an oscillating interfac e can be related to the periodic renewal of the boundary layer with th e fresh bulk liquid. The influence due to the interfacial movement gra dually diminishes towards a distance approximately twice the oscillati on amplitude measured from the equilibrium gas/liquid interfacial posi tion. It has also been found that the Nusselt number and the oscillato ry Reynolds number correlate the heat transfer data reasonably well. E xperimental results obtained using air/water interfacial waves have sh own that the local heat transfer rate is similar to those obtained usi ng the oscillating water column under the conditions of similar wave f requency and amplitude. (C) 1997 Elsevier Science Ltd.