A Comparative Analysis of Conductance Probes and High-Speed Camera Measurements for Interfacial Behavior in Annular Air–Water Flow

Abstract

Different techniques are used to analyze annular flow, but the more interesting ones are those techniques that do not perturb the flow and provide enough resolution to clearly distinguish the interfacial phenomena that take place at the interface, especially the disturbance waves (DW) and the ripple waves (DW). The understanding of these events is important because it influences the heat and mass transfer taking place through the thin film formed near the walls in this flow regime. The laser-induced fluorescence (LIF) and the three-electrode conductance probe are two commonly used techniques to study experimentally annular flow phenomena. In this paper, a set of experiments at different temperatures of 20 °C, 30 °C and 40 °C and different liquid Reynolds numbers have been performed in the annular flow regime, the characteristic of the DW and RW as average height and frequency of these waves has been measured by both techniques LIF and conductance probes. In addition, we also measured the mean film thickness. It was found that the mean film thickness and the DW height are practically the same when measured by both techniques; however, the height of the RW is smaller when measured by the conductance probe and this difference diminishes when the temperature increases.

Comparison of Refractive Index Matching Techniques and PLIF40 Measurements in Annular Flow

“…This equation system describes the relation between the thickness measured by the camera, or apparent film thickness, and the true film thickness. A deeper explanation of the procedure can be found in previous studies [13,20].…”

“…This process employs Sobel filtering with 3 × 3 convolutional kernels. For a deeper understanding of this process, refer to [20]. 6.…”

“…By incorporating a filter at the digital high-speed camera to eliminate laser wavelengths, it becomes feasible to eliminate light rays originating from the laser source and entering the camera sensor. This process yields clear images of the liquid film [20]. Consequently, high-speed cameras can be utilized to capture images of the liquid layer, which is rendered distinguishable by the phenomenon of fluorescence explained above.…”

“…Optical methods are modern techniques that are widely used to obtain results over time in a spatially distributed manner [20][21][22]. These non-invasive methods typically use high-speed cameras with high spatial resolution and can capture many frames per second.…”

“…Rivera et al [20] highlighted the challenges of refraction when measuring annular flow within a pipe. Their study mentions using the liquid box technique to mitigate these challenges.…”