Water at 20 °C is flowing with velocity of 0.5 m/s between two parallel flat plates placed 1 cm apart. Determine the distances from the entrance at which the velocity and thermal boundary layers meet.

Therefore, the distance from the entrance at which the velocity and thermal boundary layer meets is x = 0.516 m, = 1.889 m

Explanation:

The value for the property of water was obtained at 20° C from the table.

ρ = 998 Kg/

μ = 1.002 × Kg/m.s

Pr = 7.01

The waters kinematic viscosity is calculated at 20° C using the relation.

v = 1.004 × /s

The thickness of thermal boundary layer is calculated using the relations.

=

= 0.005 m

= = 0.005 m

Predict the flow is laminar,

The formula for the thickness of the velocity boundary layer is

The entrance by the distance was calculated in which the velocity boundary layer meets as shown.

The equation is rearranged.

Square Both the equations:

=

x = 0.516 m

The formula for the thermal boundary layers thickness is

=

The entrance by the distance was calculated in which the velocity boundary layer meets as shown.

Square Both the equations:

= 1.889 m

The Reynolds number value is calculated, x = 0.516 m.

Re = 2.57 × < 5 ×

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explanation: