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Homework 5

CM3110 Transport Processes I

CM3110
  1. (drag on a sphere)  Air at 102 kPa absolute pressure and 30oC flows past a sphere having a diameter of 42 mm at a velocity of 23 m/s.  What is the force on the sphere?  If air at the same pressure and velocity flows past a cylinder of the same diameter, what is the force/length on the cylinder?  If the sphere is held in the flow by a rod of diameter 3.0 mm and length 300.mm, what is the drag due to the rod?  What percent of the total force on the sphere plus rod is due to the rod?  SOLUTION
  2. (drag coefficients)  What is the difference between form drag and friction (skin) drag?  SOLUTION
  3. (drag coefficients)  What is the Reynolds number for a golf ball driven off the tee?  (search the web for estimates of the velocity).  What is the Re for a baseball pitch?  In terms of the shape of the log Cd versus Re curve, explain why golf balls are dimpled.  Should baseballs be dimpled too?  SOLUTION
  4. (packed beds) Geankoplis 3rd edition 3.1-9 p205 Water at 24oC is flowing by gravity through a filter bed of small particles having an equivalent diameter of 0.0060 m.  The void fraction of the bed is measured to be 0.42.  The packed bed has a depth of 1.50 m.  The liquid level of water above the bed is held constant at 0.40 m.  What is the water velocity based on the empty cross section of the bed?  SOLUTION
  5. (fluidized beds) (based on Geankoplis 3rd edition 3.1-12 p205)  Particles having an equivalent diameter of 0.10 mm and a density of 1200 kg/m3 are to be fluidized using air at 25oC and 202.65 kPa absolute pressure (density=2.374 kg/m3; viscosity=1.845 x 10-5 Pa s)).  The void fraction at minimum fluidizing conditions is 0.43.  The bed diameter is 0.60 m and the bed contains 350 kg of solids.  Calculate a)  the minimum height of the fluidized bed; b) the velocity at the point of incipient fluidization..  SOLUTION
  6. (compressible flow) Geankoplis 3rd edition 2.11-2 p112  Methane gas is being pumped through a 305m length of 52.5 mm inner diameter steel pipe at the rate of 41.0 kg/m2 s.  The inlet pressure is 345 kPa absolute.  Assume isothermal flow at 288.8K.  Calculate the pressure at the end of the pipe (the viscosity is 1.04 X 10-5 Pa s)  SOLUTION
  7. (compressors) Geankoplis 3rd edition 3.3-3 p207 A compressor operating adiabatically is to compress 2.83 m3/min of air at 29.4oC and 102.7 kN/m2 to 311.6 kN/m2.  Calculate the power required if the efficiency of the compressor is 75%.  Also, calculate the outlet temperature.  SOLUTION