PSV: Interconvert mass, volume, and moles (and their flows)

Mass and Flow Variables

In ChE processes there are a number of variables that typically play an important role. Let's review what some of them are.

DEFINITION:

Density is the mass of a material per unit volume (specific volume is inverse - i.e., volume per unit mass).

DEFINITION:

Specific Gravity is the ratio of one material's density to that of a reference material (typically water at 4C).

S.G. is dimensionless -> density A/density Ref.

Material moves in/out of process units -> flow rate!

DEFINITION:

The flow rate represents the amount of material that moves into (or out of) a process unit per unit time.

(TRICK)
EXERCISE:

What are the units (dimensions) of a flow rate? [cheat]

NOTE:

We can interconvert a mass or volume (and therefore a mass or volumetric flow rate) by using the density (or the specific volume) as a "conversion factor" (1 mL glass = 2.5 g glass)!

OUTCOME:

Interconvert mass, volume, and moles (and their flows)

TEST YOURSELF!

Convert the flow rate 10 g water per hour to L/h. How about mole/h?(if you can't we'll review that next lecture!)

Measuring flow rates

rotometer

NOTE:

Typically one measures volumetric flowrates even though we are more often interested in mass flowrates.