This paper presents results from a programme of steady-state natural circulation tests carried out on a two-tube experimental boiler. The circuit was constructed using normal commercial tubes and the tests covered the following range of variables: During the tests, measurements were taken of pressure, pressure difference, circulation rate, and density or void fraction at the top of the riser tube. The void fraction data are presented for use. A theoretical analysis was carried out using an annular type flow model in the riser tube with a simple two-phase friction pressure drop expression which required only void fraction data. A comparison was made between the theoretical results and the experimental data and the comparison was extended to include ( a) homogeneous flow, ( b) Martinelli–Nelson correlation, and ( c) Thom correlation. The results indicate that the analysis used, which requires only void fraction data, gave the best correlation over the range of natural circulation conditions covered.
Flow regimes in a simplified Taylor–Couette-type flow model