Lesson 7 - Principles of Fluid Mechanics 3 SAQ
This lesson allows you to test yourself on the material covered in the lesson on Principles of Fluid Mechanics 3, and to determine the level to which you have met the learning outcomes.
Self-Assessment Questions
1. * Determine the relative roughness of a pipe with an internal diameter of 15 mm and an absolute roughness of 0.05 mm.
2. */** A yeast pitching main has an internal diameter of 80 mm. If a maximum average line velocity of 0.5 m/s is specified, what would the friction factor be and consequently, the pressure drop per metre due to friction alone?
The yeast slurry can be considered a Newtonian fluid with a constant dynamic viscosity of 0.05 kg/ms and a density of 1,300 kg/m3.
3. ** Consider further, the yeast pitching main in question two above. Prior to yeast pitching, interface water flows down the yeast main at the same maximum average velocity. What would be the pressure drop per metre?
The absolute roughness is 0.002 mm. (µ = 1x10-3 kg/ms and ρ = 1,000 kg/m3).
4. ** During a design meeting for refitted CO2 bung lines (the CO2 vent lines from a fermenter), you are offered two sizes (a 50 mm or a 65 mm internal diameter). The maximum gas flowrate is expected to be 180 kg/h, and the maximum line length will be 65 m. The frictional pressure drop over the line must be kept below 5 kPa to limit excessive fermenter headspace pressure. Which line diameter would you choose and why?
Assume a surface roughness of 0.05 mm; ρ = 1.9 kg/m3; and µ = 15 x 10-6 kg/ms.
5. **/*** A bright beer tank has a beer depth of 2.5 m and a headspace pressure of 1 bar g. A 15 mm diameter sample valve is located 0.5 m above the base. It is left partially open (with a loss coefficient of 200). By considering the valve loss coefficient only, what would be the initial flowrate of beer through the valve? (Beer ρ = 1,005 kg/m3).