Measurements of two-dimensional bubble properties in a three-phase fluidized bed were made using an electroresistivity probe. The effects of fluid flow rate, particle size and the vertical height over the distributor on the bubble size, frequency and rising velocity were determined.
The bed contraction was observed in a bed of 1.5 mm glass beads at lower gas flow rate. The bubble frequency decreased and the frequency distribution became wider with the height above distributor.
In the present systems, the bubble breakup was due to the particle penetration from the bubble roof when large particles were mixed in a bed of small particles. (the half of minimum disturbance wave length was above 0.8 cm.)
From the analysis of data, the bubble size increased inversely with the particle size and the functional relationship was given under the present experimental conditions as follows;
ℓ=1.325 $U_b^{0.230}Ug^{0.353}dp^{-0.567}$
The empherical correlation for the bubble rising velocity was presented as a function of experimental variables ;
$Ubr = 43.045\ell^{0.417}U_b^{0.050}Ug^{0.137}dp^{0.187}$
Electroresistivity probe 를 이용하여 2차원 삼상유동층의 bubbles의 물리적 특성을 고찰하였다. bubble의 크기, 상승속도, volume fraction및 frequency에 미치는 fluid velocity, bed 높이의 영향을 검토하였다. gas-liquid system에서의 bubble의 특성도 아울러 검토하였다.
1.5 mm glass beads의 유동층에서 낮은 기상유속에서 bed contraction 이 관찰되었으며 bubble의 frequency는 bed 높이에 따라 감소하고 gas flow rate가 클수록 size distribution이 넓은 분포를 가졌다.
Bubble의 breakup mechanism은 본 실험범위 (Ug ; 0.8∼12.1 mm/$\sec, U_\ell 0∼7.72 cm/\sec$)에서는 Taylor instability 뿐만아니라 큰 particle을 작은 particle의 bed에 혼합하였을 때 particle penetration에 의한 bubble splitting도 일어날 수 있음을 밝혔다. bubble의 크기는 particle의 입자 크기에 영향을 받으며 각 실험변수간에
$\ell = 1.325 U_\ell^{0.230} Ug^{0.353} dp^{-0.567}$
과 같은 경험식이 적용된다. 한편, bubble의 상승속도에 대해 bubbles의 크기, particle의 크기, 유체의 유속등에 대해 다음과 같은 실험식을 얻었다.
$U_{br} = 43.045\well^{0.471} U_ℓ^{0.050} Ug^{0.137} dp^{0.187}$
