Liquid film dynamics of two-phase annular flow in square and tight lattice subchannels

The flow behavior of a liquid film on the wall in square-lattice and tight-lattice double subchannels was studied by using a pair of flexible liquid film sensors based on the electrical conductance method. The liquid film sensor has a network of electrodes on the surface and the electrical conductance between transmitter and receiver electrodes is detected by using a high-speed wire-mesh measurement system. The sensors were fixed on rod simulators with 20 mm diameter and the liquid film thickness distribution was estimated from the measured conductance data array. With this method, it is possible to observe the flow structure of the liquid film with a high sampling speed up to 10 kHz and a spatial resolution of 2 mm. In the present study, the spatial-temporal distributions of liquid film thickness in the annular flow in a square-lattice and a tight-lattice pair of adjacent subchannels were measured by using two liquid film sensors installed on the surface of opposing rods. The traveling of disturbance waves was observed in the time-series of two-dimensional film thickness distributions. The interaction of the liquid films on the opposing rods was investigated by correlating the signals of both sensors. As a result, the effect of the channel geometry on the averaged film thickness profiles and the correlation characteristics was analyzed for the first time.