Figure 3. The variations of pressure drop and standard deviation with liquid mass flow rate (G = 0.126 kg·m-2·s-1) (a)us = 1 mm·s-1, (b)us = 2 mm·s-1, (c)us = 3 mm·s-1, (d)us = 5 mm·s-1
In order to establish the transition boundary between trickle flow and pulse flow in the three-phase moving bed, several combinations of gas and liquid mass flow rate in a broad range were adopted at different solid flow rates. Based on the standard deviation and the visual observation methods, the transition boundary between the trickle flow and the pulse flow in the three-phase moving bed was distinguished and shown in Figure 4. As can be seen from Figure 4 that the transition boundary between the trickle flow and pulse flow tends to decrease as the liquid mass flow rate increases at any given solid flow rate. This result is coherent with the observations in the trickle bed reported by several authors18,21,40,41. It is worth noting in Figure 4 that the transition depends strongly on the solid flow rate. At the constant gas mass flow rate, the increase of the solid flow rate makes the transition boundary shift rightwards to a higher liquid mass flow rate.