Thermal diffusion response to gas–liquid slug flow and its application in measurement

Abstract

A novel on-line, contactless and nearly non-intrusive measurement method based on thermal diffusion is proposed for gas–liquid slug flow in this paper. Temperature fluctuations of a pipe wall heated at a constant heat flux are induced by Taylor bubbles and liquid slugs due to their different heat exchange capacities. The slug flow characteristics, including velocity, length, and frequency, in the vertical pipe, can be obtained through temperature fluctuation detection. Correlations between wall temperature fluctuations and slug flow characteristics are developed. Through experimental tests on air–water slug flow in a 25 mm diameter pipe at the atmospheric pressure of 1 bar and room temperature of approximately 20 °C, the average relative errors in average velocity for the Taylor bubbles and liquid slugs are 1.84% and 2.28% with maximum values of 4.67% and 5.79%, respectively. The average relative errors in average length are 4.65% and 3.68% with maximum values of 12.75% and 10.48%, respectively, under the conditions of 0.16–0.65 m/s of gas superficial velocity, 0.22–0.49 m/s of liquid velocity, and 0.34–2.96 of gas–liquid ratio.