a method for detecting bubbles in two-phase gas-liquid flow

Bubble detecting bubble has been a basic issue in two-phase flow systems. in this paper, a new method for measuring the frequency of bubble formation is presented. for this purpose, an electronic device is designed and constructed to work based on a change in intensity of the laser beam. continues light beam is embedded just above the needle, which is received by a phototransistor. when bubbles go through the light beam, they make a deviation on it and change its intensity. so, the electrical resistance between two bases of phototransistor changes, and this variation is sensed by an electronic board. based on the number of interruption and duration time, the frequency of bubble formation is be calculated. liquid and gas phases in the present work are water and air, respectively. tests are performed in constant liquid height (60 mm above the needle), constant needle diameter (1.6 mm), and gas flow rates between 50 to 1200 ml/hr. also, three other methods are utilized to measure the bubble frequency: image processing (ip), numerical modeling, and theoretical model. results show that with an increase in the flow rate of the gas phase, the frequency of formation increases approximately in a linear manner. validation of methods with ip method shows that the new device has very good accuracy for measuring bubble formation frequency. so because of the simplicity of using and low cost, it can be a superseded method of image processing.