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Basics of Fluid Mechanics, 2014a

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13.8. SOLID–LIQUID FLOW 551<br />

where Ξ is Martinelli parameter.<br />

It is assumed that the pressure loss for both phases are equal.<br />

dP<br />

dx ∣ = dP<br />

SG<br />

dx ∣ (13.44)<br />

SL<br />

The pressure loss for the liquid phase is<br />

dP<br />

dx ∣ = 2 f L U 2 L ρ l<br />

(13.45)<br />

L<br />

D L<br />

For the gas phase, the pressure loss is<br />

dP<br />

dx ∣ = 2 f G U 2 G ρ l<br />

(13.46)<br />

G<br />

D G<br />

Simplified model is when there is no interaction between the two phases.<br />

To insert the Diagram.<br />

13.8 Solid–Liquid Flow<br />

Solid–liquid system is simpler to analyze than the liquid-liquid system. In solid–liquid,<br />

the effect <strong>of</strong> the surface tension are very minimal and can be ignored. Thus, in this<br />

discussion, it is assumed that the surface tension is insignificant compared to the gravity<br />

forces. The word “solid” is not really mean solid but a combination <strong>of</strong> many solid particles.<br />

Different combination <strong>of</strong> solid particle creates different “liquid.” Therefor,there<br />

will be a discussion about different particle size and different geometry (round, cubic,<br />

etc). The uniformity is categorizing the particle sizes, distribution, and geometry. For<br />

example, analysis <strong>of</strong> small coal particles in water is different from large coal particles in<br />

water.<br />

The density <strong>of</strong> the solid can be above or below the liquid. Consider the case<br />

where the solid is heavier than the liquid phase. It is also assumed that the “liquids”<br />

density does not change significantly and it is far from the choking point. In that case<br />

there are four possibilities for vertical flow:<br />

1. The flow with the gravity and lighter density solid particles.<br />

2. The flow with the gravity and heavier density solid particles.<br />

3. The flow against the gravity and lighter density solid particles.<br />

4. The flow against the gravity and heavier density solid particles.<br />

All these possibilities are different. However, there are two sets <strong>of</strong> similar characteristics,<br />

possibility, 1 and 4 and the second set is 2 and 3. The first set is similar<br />

because the solid particles are moving faster than the liquid velocity and vice versa for<br />

the second set (slower than the liquid). The discussion here is about the last case (4)<br />

because very little is known about the other cases.

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