Research of condensation induced water hammer under filling a horizontal pipe with subcooled water

Experiments at the KGU test facility, devoted to condensation induced water hammers (CIWH) were analysed with the WAHA code. Test section of the KGU test facility is slightly inclined horizontal pipe of 3 m length and of 64 mm inner diameter. Subcooled water was supplied to the pipe inlet, pipe outlet was connected to separator vessel. Upper part of separator vessel was connected to steam source. Experiments were performed for different system pressure, different water subcooling and different mass flow rate of water supply. The performed experimental study of CIWH showed that in the investigated range of parameters, the development of CIWH occurs in different ways. At the stage of water propagation along the filled with steam horizontal pipe, water hammer was not observed. At the stage of free drainage of water from the outlet end of the pipe, water hammer was realized only when the water was sufficiently subcooled. At the stage of the water level rise in the horizontal pipe, water hammer occurred in all tests. At the last stage of filling the upper part in the separation vessel, there were small water hammers due to the collapses of the remaining steam bubbles. Numerical modelling of these experiments with the WAHA code revealed the shortcomings of the interphase heat transfer model developed for this code, which have a noticeable effect on the numerical solution.

Plume Stability During Direct Contact Condensation of Steam in a Crossflow of Subcooled Water, At High Mass Flux and with a Small Nozzle Diameter

The stability of a steam plume during direct-contact condensation is investigated into a crossflow of subcooled water with mass fluxes that are higher (>600 kg/m2s) and a nozzle diameter (2.4 mm) that is smaller than typically seen in the literature. The transition from a stable steam plume to an unstable plume associated with the formation and collapse of steam bubbles is characterized by high-speed imaging and high-frequency pressure measurements. Four regimes are observed: stable, condensation oscillation, transition, and unstable. A regime map and spectral signatures of the different flow regimes are provided. Results are compared with correlations from the literature, which are typically derived for lower mass fluxes, larger nozzles, and injection into stagnant pools of water.

The pulsating nature of bubble boiling of subcooled water flow during cooling of a metal heater

This paper presents the results of an experimental study of the subcooled water flow boiling on the surface of a metal rod 12 mm in diameter. As a result of the rapid heat release that occurs when an electric current is pulsed through a metal heater, the latter reaches certain temperature levels above the saturation temperature of water at the corresponding pressure (p = 0.17 MPa). In a system formed by a cold liquid and a heated solid body, the process of intense heat exchange begins, the cooling rate of the metal in which reaches its maximum when the nucleate boiling is realized. Interest in such scenarios is remaining high and is caused by the need for quantitative prediction of the characteristics of nucleate boiling and the existence boundaries of this boiling mode. As well-known, nucleate boiling is limited from above by the onset of film boiling and from below by the required surface temperature for which a significant number of nucleation centers are activated. The pressure waves arising during film boiling have a significant amplitude, as a result of which special conditions of interphase interactions may occur. The results of the study showed that self-oscillating pressure pulsations may occur which is associated with the nucleate boiling in an annular channel.