Liquid holdup measurement in horizontal oil–water two-phase flow by using concave capacitance sensor

•We study the concave capacitance sensor for horizontal oil–water two-phase flow.•We calculate the static response for different flow patterns and optimize the sensor.•We conduct experiment to study the characteristics of the concave capacitance sensor.•The sensor shows good performance for the dispersion of water in oil flow.•The sensor has high sensitivity when the oil holdup is larger than 60%. Due to the complex flow structures of horizontal oil–water flows, the liquid holdup measurement is still a challenging problem. In this paper, we using the finite element analysis build a two-dimensional model of the concave capacitance sensor and investigate the effect of sensor geometry on the distribution of the sensitivity field. Through calculating the sensor static response for different horizontal oil–water flow patterns, we figure out the optimum geometry of the concave capacitance sensor. In addition, we conduct experiment to obtain the measured response of the concave capacitance sensor and achieve the oil-holdup by using quick closing valve. The results indicate that the optimized concave capacitance sensor shows good performance for liquid holdup measurement of horizontal oil–water two-phase flow.