Acoustic enhancement of direct-contact condensation using capillary waves


Direct-contact condensation of a vapor bubble train rising in a subcooled liquid bath is accelerated using sonic [O(1 kHz)] acoustic actuation of the liquid-vapor interface. The actuation couples with the characteristic wavelength of the capillary (Faraday) surface instability to form waves which disrupt the interfacial thermal boundary layer, thereby enhancing heat transfer from the bubble to the surrounding subcooled liquid and accelerating vapor condensation, significantly reducing vapor volume. It is shown that the acoustically-induced surface waves lead to bi-directional penetration of fingers of subcooled liquid and vapor across the interface and the small-scale interfacial mixing caused by this motion disrupts the nominally conduction-limited heat transfer and leads to a pronounced, rapid reduction in vapor volume. It is also shown that the acoustic actuation is effective at reduced ambient pressures (e.g., in power cycle condensers) and during co-located boiling and condensation in pool boiling over submerged heater surfaces. Such acoustically-enhanced condensation may enable reduction in the volume of the subcooled liquid bath and therefore in the overall scale of direct-contact condensers in various configurations.

In International Journal of Heat and Mass Transfer