Ch 4. Energy Analysis     Multimedia Engineering Thermodynamics
Steady-flow
Process		 Steady-flow
Devices (1)		 Steady-flow
Devices (2)		 Steady-flow
Devices (3)		 Unsteady-flow
Process		      
Thermodynamics
 Steady-flow Devices (1) Case Intro Theory Case Solution  
 Chapter
 1. Basics
 2. Pure Substances
 3. First Law
 4. Energy Analysis
 5. Second Law
 6. Entropy
 7. Exergy Analysis
 8. Gas Power Cyc
 9. Brayton Cycle
 10. Rankine Cycle
 
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Author(s):
Meirong Huang
Kurt Gramoll
 
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THERMODYNAMICS - CASE STUDY
    Introduction


The Wind Tunnel



Consider the Diffuser as a
Control Volume

 

Belinda is a member of the race car club at her university. The club has a trip to the wind tunnel laboratory to view the testing of a new race car. A diffuser is used to slow the air flow and exhaust it. The engineer working there told them that for safety considerations, the velocity at the exit of the diffuser should be less than 3 m/s. But the temperature has not been checked. If the temperature is higher than 35oC, it will be harmful to the environment. Is the air from the wind tunnel safe to exhaust after flowing through the diffuser?

What is known:

  • Air temperature at diffuser inlet T1 = 10 oC
  • Pressure of air at diffuser inlet P1 = 80 kPa
  • The mass flow rate = 200 kg/s
  • The inlet area of the diffuser A1= 1.5 m2
     
    Questions


 
  • Determine the velocity of the air at the inlet of the diffuser
  • Determine the temperature of the air leaving the diffuser
     
    Approach
    Consider the diffuser as a control volume. It is a one-inlet-one-exit system. During the test process, the flow can be treated as steady.