Development of a subchannel void sensor and two-phase flow measurement in 10 × 10 rod bundle

An accurate and detailed experimental database is crucial for modeling the multidimensional two-phase flow and for validating the numerical calculation results. In particular, a two-phase flow in the rod bundle flow channel is so complicated that it is difficult to measure a multidimensional flow structure. Based on the available reference, a point-measurement sensor for acquiring void fractions and bubble velocity distributions do not infer interactions of the subchannel flow dynamics, such as a cross flow and flow distribution, etc. In order to acquire multidimensional two-phase flow in a 10 × 10 rod bundle with an o.d. of 10 mm and length of 3110 mm, a new sensor consisting of 11 × 11 wire and 10 × 10 rod electrodes was developed. The electrical potential in the proximity region between the two wires creates a void fraction in the central subchannel, like a so-called wire-mesh sensor. A unique feature of the devised sensor is that the void fraction near the rod surface can be estimated from the electrical potential in the proximity region between one wire and one rod, meaning the additional 400 points of void fraction and phasic velocity in the 10 × 10 rod bundle can be acquired. The devised sensor demonstrates multidimensional flow structures, i.e. void fraction, phasic velocity, sauter mean diameter and interfacial area concentration distributions. Acquired data exhibit complexity of two-phase flow dynamics in a rod bundle flow channel, such as coalescence and the breakup of bubbles in transient phasic velocity distributions.

► We have developed a new sensor to acquire two-phase flow in a 10 × 10 rod bundle flow channel.
► The devised sensor measures 121 points of the void fraction in the central subchannel region.
► A unique feature of the sensor is 400 points of void fraction near the rod surface can be measured.
► The sensor is applied to the air–water two-phase flow measurement in the 10 × 10 rod bundle.
► The sensor demonstrates a developing process of a multidimensional two-phase flow dynamics.