Particle size influence on effective permittivity of particle-gas mixture with particles agglomeration: Experimental study

Concentration measurement of a particle-gas mixture by using a capacitance sensor is based on the effective medium approximation (EMA) theory, regardless of particle size. In existence of particles agglomeration or aggradation, however, the effective permittivity of the mixture was found dependent on particle size. In this paper, a parallel plate, differential capacitance sensor was utilized to investigate the influence of particle size on the effective permittivity of the mixture in such a case. Static experiments using three materials including glass, limestone and quartz particles were carried out in an off-line manner. The volume fraction of particles being tested ranged from 20 to 600 ppm, while the particle size was between 3 and 100 μm. Experimental results showed that the effective permittivity of a particle-gas mixture with particles agglomeration is larger than that predicted by EMA and the smaller the particle size, the larger the effective permittivity. The experiments and results were detailed and discussed in the paper.