Atmospheric air at 25 °c and 8 m/s flows over both surfaces of an isothermal (179c) flat plate that is 2.75m long. determine the heat transfer rate per unit from the plate for 3 width different values of the critical reynolds number: 100,000; 500,000; and 1,000,000

Re=100,000⇒Q=275.25

Re=500,000⇒Q=1,757.77

Re=1,000,000⇒Q=3060.36

Explanation:

Given:

For air      =25°C  ,V=8 m/s

  For surface =179°C

     L=2.75 m    ,b=3 m

We know that for flat plate

⇒Laminar flow

⇒Turbulent flow

Take Re=100,000:

 So this is case of laminar flow

From standard air property table at 25°C

  Pr= is 0.71  ,K=26.24

So    

Nu=187.32   ()

187.32=

     ⇒h=1.78

heat transfer rate =h

                           =275.25

Take Re=500,000:

So this is case of turbulent flow

Nu=1196.18  ⇒h=11.14

heat transfer rate =h

                             =11.14(179-25)

                           = 1,757.77

Take Re=1,000,000:

So this is case of turbulent flow

Nu=2082.6  ⇒h=19.87

heat transfer rate =h

                             =19.87(179-25)

                           = 3060.36

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