Unit Operation Final Exam (6/23/2021) – Exam I
Please scan or take a photo of your hand-written answer sheet and upload the electronic file on time.
Q1. In chemical plants, towers are usually lifted a few meters away from the ground. Why? (10%)
Q2. Determine the relationship between the average velocity and maximum velocity within a smooth circular
pipe flowing with a turbulent flow, which follows Prandtl's power law with n=10. (15%)
Q3. A problem showed up in a chemical process, and one of your colleagues guesses that this problem may come
from a broken orifice meter. This orifice meter (d = 38 mm) is installed in a pipe (d = 50 mm) to handle a flow
of glycerol, which has a density of 1250 kg/m3 and a viscosity of 50 mN-s/m2. The orifice meter is now showing
a pressure reading of 580 Pa. To check this guess, you inserted a pitot tube at the center of the pipe, and you found
that the pressure reading of the pitot tube is 920 Pa. Is the opinion from your colleague correct? Prove whether
the orifice meter is broken (25%).
Q4. 1250 cm3/s of water is to be pumped through a cast iron pipe, 1-inch diameter and 30 m long, to a tank 12 m
higher than its reservoir. Calculate the power required to drive the pump, if the pump efficiency is 60%. If this is
a centrifugal pump with a β of 45 degree, a fan’s radius of 0.3 m, and a fan width of 0.2 m, what is the rotation
speed of the pump (in RPM)? Viscosity of water = 1.30 mN-s/m2. Density of water = 1000 kg/m3 (25%).
Q5. Water (viscosity=1.3 mN-s/m2; density=1000 kg/m3) flows in a galvanized iron pipe (d=6 inches) with a
length of 10 m. The required flow rate is 1.5 kg/s. To measure the flow rate, an orifice meter (orifice diameter=4.2
inches) is installed at a part of the pipe to ensure that a constant reading of 1.5 kg/s can be maintained. Calculate
the power required to overcome the friction loss from the orifice and pipe (25%).