Condensing Heat Transfer in Steam-Water Condensing-Injector

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Abstract
An experiment on the direct heat transfer process between supersonic steam and subcooled water jet was performed, using a steam-water condensing-injector. Photographic observation provided information on the state of flow, and establishment of a critical separate steam-water flow was confirmed. The temperature and pressure distributions along the flow were measured and the effective coefficients of condensing heat transfer were evaluated from the observed data, based on a model embodying an idealized interface between vapor and liquid. In the vicinity of the water nozzle exit, where the vapor-liquid interface was distinct, the heat transfer coefficients obtained were 14–28 (cal/°C.cm2.sec), and some correlation was observed among Nusselt, Reynolds and Jakob numbers, upon adopting the velocity and the physical properties of the steam phase. The relations Nu=6.0.Re 0.9(Pr=1.04–1.10), and Re=1.8×108.Ja 3.0, i.e., Nu=1.6×108.Ja 2.7 were derived as a rough estimation. No clear correlation could be discerned in the corresponding data obtained from observation points further downstream, where a distinct steam-water interface no longer existed. In conclusion, it is proposed that, in deriving the correlations between Nu and Re or Ja, the physical properties of the vapor and the vapor-liquid relative velocity should be adopted, on account of the strong dependence of condensing heat transfer on steam velocity and water subcooling.

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