Simulative and Experimental Studies: Void Fraction Detection in a Bubble Column of a Conducting Pipe

In this paper, we present simulative and experimental studies into ultrasonic sensors to provide void fraction measurements in a chemical bubble column using the ultrasonic tomographic (UT) technique. First, the UT laboratory setup is discussed. A finite element (FE) analysis was performed according to the physical dimensions of the UT system. Degradation of ultrasonic energy was estimated mathematically through coefficients of incident waves. By using the FE frequency-domain approach, the effects of emission frequency on the UT platform were further investigated. The sensing electronic design and the procedures of data processing with a back projection image algorithm were discussed. Experiments in measuring void fractions inside a bubble column of the stainless-steel pipe were conducted where the test conditions were controlled either by capillary, syringe, or air pump. Statistical engineering methods, including the normality test and box-plots, were applied to validate the experimental data. It was found that the experimental data were normally distributed and the measurements of void fraction were proportional to the pump rate. In conclusion, ultrasonic sensors with high emission frequency that resulted with redistribution energy (kHz range) can be used in a tomographic system for void fraction inspection of a bubble column in the stainless-steel pipe.