Direct Contact Condensation (DCC) is a special mode of condensation where condensation
occurs on the interface between steam and water. The condensation of steam injected into water is one
of the least studied forms of condensation. Nevertheless, there is a range of devices which rely heavily
on effective use of DCC, such as steam driven jet pumps, steam ejectors and safety valves in nuclear
reactors. Therefore, correct prediction and modelling of DCC behaviour are crucial to obtain an
optimised design of such devices. In this chapter the process of the DCC of steam injected into water is
described in details, where different regions of the process will be presented. The process is compared
with other modes of condensation and is described as one of the multi-phase flows. In addition, an
analytical model for DCC is presented. Furthermore, the chapter focuses on the behaviour of injected
steam, commonly termed as a regime. Different regimes of DCC are presented in details and parameters
that determine the DCC regime are discussed. A three dimensional condensation regime diagram is
presented, where the DCC regime is shown as a function of steam inflow rate, temperature of the water
subcooling and steam injector diameter size. After that, the penetration distance of steam into water or a
steam plume length is discussed and a two dimensional steam plume length diagram is presented. The
diagram shows the length of the steam plume in relation to the steam Reynolds number and the
condensation potential.
Keywords: Direct contact condensation, condensation regime, regime map, steam plume length.