Flow structure of subcooled boiling water flow in a subchannel of 3x3 rod bundles

In this paper, the interfacial flow structure of subcooled water boiling flow in a subchannel of 3x3 rod bundles is presented. The 9 rods are positioned in a quadrangular assembly with a rod diameter of 8.2 mm and a pitch distance of 16.6 mm. Local void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter, and liquid velocity have been measured using a conductivity probe and a Pitot tube in 20 locations inside one of the subchannels. A total of 53 flow conditions have been considered in the experimental dataset at atmospheric pressure conditions with a mass flow rate, heat flux, inlet temperature, and subcooled temperature ranges of 250-522 kg/m² s, 25-185 kW/m², 96.6-104.9degC, and 2-11 K, respectively. The dataset has been used to analyze the effect of the heat flux and mass flow rate on the local flow parameters. In addition, the area-averaged data integrated over the whole subchannel have been used to validate some of the distribution parameter and drift velocity constitutive equations and interfacial area concentration correlations most used in the literature. (author)