Nonlinear analysis of characteristic frequencies and chaotic behavior of flow patterns during flow boiling of hydrocarbons in a small channel

The dynamics of time series obtained from an optical sensor for analysis of flow patterns has been investigated during flow boiling of hydrocarbons in a horizontal tube with 1 mm inner diameter. The tests were performed with the refrigerants R-600a, R-290 and R-1270 at 17 degrees C saturation temperature, with mass flux ranging from 240 to 480 kg/(m(2)s), considering heat fluxes between 5 and 60 kW/m(2). Five flow patterns were identified, and their characteristic frequencies were investigated and related to dynamics of the liquid-vapor morphology over time. Results also show different long memory trends based on time series and nonlinear chaotic behavior has been observed. (C) 2019 Elsevier Ltd. All rights reserved.