The effects of solid concentration and liquid viscosity on bubble properties such as bubble size and bubble rising velocity were measured with a dual-electroresistivity probe in a slurry bubble column of 0.15 mdiameter. The behavior of volume-surface mean bubble diameter, dvs, was analyzed. By addition of solid particles at small gas velocity, the bubble size distribution shifted to a large-size region and the bubble velocity distribution shifted to a large-velocity region. At the same time, the flow pattern changed from homogeneous flow to heterogeneous flow. The effect of solid particles on bubble size, however, became small as the particle diameter decreased or the liquid viscosity increased. The following equation was derived to estimate dvs. dvs = 0.59( VDlsg)2lg where VDis the drift flux of gas, sg is the cross-sectionally averaged gas holdup and g is the gravitational acceleration.

Experimental work was conducted to investigate the effect of particle size and particle density upon the wall-to-bed heat transfer characteristics in liquid-solid fluidized beds with a 95.6 mrn column diameter over a wide range of operating conditions. The radial temperature profile was found to be parabolic, indicating the presence of a considerable bed resistance. The effective radial thermal conductivity and the apparent wall film coefficient were obtained on the basis of a series thermal resistance model.The modified Peclet number of the radial thermal conductivity decreases upon the onset of fluidization, has a minimum at a bed porosity of 0.6 to 0.7 and increases with further increase of bed porosity. The modified Peclet number decreases considerably with decreasing particle size or increasing particle density. The apparent wall heat transfer Coefficient can be represented well by a Colburn j-factor correlation over a wide range of data as follows:A close analogy is found to exist between the modified j-factor for wall heat transfer coefficient and that for wall mass transfer coefficient, in liquid-solid fluidized beds.

Wall to bed heat transfer has been studied in three‐phase fluidized beds with a cocurrent up‐flow of water and air. Six sizes of glass beads, two sizes of activated carbon beads and one size of alumina beads, varying in average diameter from 0.61 to 6.9 mm and in density from 1330 to 3550 kg/m3, were fluidized in a 95.6 mm diameter brass column heated by a steam jacket. Complementary heat transfer experiments have been performed also for a gas–liquid cocurrent column and liquid–solid fluidized beds. The wall‐to‐bed coefficient for heat transfer in the gas–liquid–solid fluidized bed is evaluated on the basis of the axial dispersion model concept. The ratio of the wall‐to‐bed heat transfer coefficient in the gas–liquid–solid fluidized bed to that in the liquid–solid fluidized bed operated at the same liquid flow rate is correlated in terms of the ratio of the velocity of gas to that of liquid and the properties of solid particles. A correlation equation for estimating the wall‐to‐bed heat transfer coefficient in the liquid–solid fluidized bed is also developed.

The wall-to-liquid mass transfer coefficient, kw, was measured for both surfaces of a coaxially immersed tube and a column wall in packed and fluidized bed systems with gas-liquid concurrent up flow. Supplementary measurements of kw were carried out in openpipe liquid flow, gas-liquid two-phase up flow and packed and fluidized beds with single liquid flow. The value of kwin the three-phase fluidized bed increased with increasing gas flow rate, deviating from the value in the liquid-solid fluidized bed and approaching the value in the gas-liquid two-phase up flow, while it passed through a maximumvalue with respect to the liquid flow rate. The value of kw in the packed-bed operation increased with increasing liquid flow rate and with increasing gas flow rate. The values of kw for the inner tube and the columnwall were shownto agree with each other. The values of kw in all the gas-liquid, liquid-solid and gas-liquid-solid systems examined were correlated well by a unified equation in terms of the energy dissipation rate per unit mass of liquid.An analogy existed between wall heat transfer and wall mass transfer in all the multiphase flow systems examined.

Bubble properties such as gas holdup, bubble frequency, bubble length and bubble rising velocity in a slurry bubble column were measured by using a dual electroresistivity probe method. The radial distribution of local gas holdup, sg9 was parabolic in the range, where mean solid holdup, ss, was less than 0.2. In the range of es>0.2, however, sg in the region of dimensionless radius, r//?w, from 0.4 to 0.8 decreased considerably owing to the concentration of bubbles in the central region of the column. The value of cross-sectionally averaged gas holdup, sg, agreed fairly well with that predicted by Koide's equation for heterogeneous flow in a slurry bubble column.The cumulative bubble length distribution, F» followed a log-normal distribution.On the other hand, the cumulative bubble rising velocity distribution, Fv, followed a normal distribution. The superficial gas velocity, Ug9 had little effect on Ft and Fv in the slurry bubble column with high solid content. WhenUg was larger than about 4cm/s, the median of Fl and that of Fv in the slurry bubble column were larger than the corresponding values in the bubble column. On the other hand, the variance of Ft in the slurry bubble columnwas almost the same as that in the bubble column and the variance of Fv in the slurry bubble column was smaller than that in the bubble column.