Virtual mass coefficient fluidized beds

Various model parameters involved in the derivation of the stability criterion need to be specified in order to use the stability criterion for quantitative predictions. Model parameters essential for this purpose include the slip velocity, the virtual mass coefficient, and the dispersion coefficient. The procedure for estimation of these parameters is given for gas-solid (and solid-liquid) fluidized beds and bubble columns. 

In the case of solid-liquid fluidized beds, the effect of virtual mass is to make the bed more unstable as shown in Fig. 21. This can be explained as follows The effect of virtual mass is to increase the apparent density of the particle. As discussed in this section earlier, an increase in the particle density makes the system more unstable. This observation is consistent with Fig. 21. As the particle density increases, say, ps - 9000 kg/m and Pl = 1000 kg/m, the effect of virtual mass is negligible and the curves are seen to merge irrespective of the formulation of virtual mass coefficient. 

In the case of gas-solid fluidized beds, the effect of virtual mass coefficient is negligible as shown in Fig. 22. However, as the gas density increases the effect of virtual mass becomes similar to that observed in solid-liquid systems as shown in Fig. 23. 

Fig. 21. Effect of formulation of virtual mass coefficient on lower particle critical diameter solid-liquid fluidized beds a = 3.0, /tl = 1 mPas, pi = 1000 kg/m ].

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