ENGR 260 Sections 5'1

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ENGR 260Sections 5.1
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Announcements

• Exam 2 on Wednesday
• Sections 3.1 4.5
• HW Due on Wednesday
• Tutor on Monday 1-5 PM

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Conservation of Mass

• If I mix 2 lb of sugar in 20 lb of water the
  result will be 22 lbs of a sugar / water mixture.
  
• Like energy mass is conserved.
• What about pressure, volume, temperature?

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Conservation of Mass

• Closed system ?m0
• Control Volumes Mass can flow across boundaries

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Mass Flow Rates
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Flow in Pipes
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Volumetric Flow Rates
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Volumetric Flow
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Conservation of Massin Control Volumes
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Steady Flow Processes

• Mass in per unit time Mass out per unit time

• When can this assumption be made?

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Incompressible Flow

• When can this assumption be made?

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Example 1

• You have a 500L tank that is 200L full. The flow
  rate into the tank is 10 L/s and the flow rate
  out of the tank is 5 L/s.
• How long before the tank overflows?

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Example 2

• It takes 20 seconds to fill a 5 liter bucket with
  a hose that is 2 cm in diameter with a nozzle
  that is 0.8 cm.
• Determine
• Mass Flow Rate (kg/s)
• Volumetric Flow Rate (m3/s)
• Velocity of water in the hose (m/s)
• Velocity of water in the nozzle (m/s)

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Example 3

• Air at 200 kPA and 25C flowing through a pipe
  at 7 m/s is heated and expanded. The exit
  conditions are 150 KPA and 50C. The radius of
  the pipe is 0.25m.
• Determine
• Mass flow rate at the inlet (kg/s)
• Volumetric flow rate at the inlet (m3/s)
• Volumetric flow rate at the outlet (m3/s)
• Velocity of the air at the exit (m/s)