Direct Contact Condensation of Steam in Subcooled Water

Abstract

Direct contact condensation (DCC) of steam in subcooled water is a phenomenon which is experienced in many applications such as thermal, chemical and nuclear engineering, particularly in energy generation devices since it enables immense energy transfer via the two-phase interface. However, under certain situations, steam water direct contact can lead to rapid condensation and result in fast (of the order of acoustic time scale) pressure transients which could have serious implications on structural integrity and safety, especially in nuclear power plants. Therefore, understanding of the underlying physics and characteristics of DCC phenomenon has a paramount importance. DCC is a complex thermo-hydraulic event in which the phase change process is governed by the interplay between several thermo-mechanical factors (e.g. local heat transfer coefficient, interfacial area density, turbulence intensity in the liquid phase) across the phasic interface. In this chapter, different situations of the DCC events, their characteristics and underlying mechanisms are discussed in detail. A detailed review of the earlier works which includes both system-level and interface scale modelling of the phenomena is also addressed in this chapter. An emphasis is given on the DCC events which are always associated with the large amplitude pressure spikes such as chugging and condensation-induced water hammer.