Air at 1 atm and 20 c is flowing over the top surface of a .2x.5 m thin metal foil. the air stream velocity is 100 m/s and the metal foil is heated electrically with a uniform heat fluz of 6100 W/m2. If the friction force on the metal foil surface is 0.3 N, determine the surface temperature of the metal foil. Evaluate the fluid properties at 100°C.

The surface temperature of the metal foil is 453.645 K

Explanation:

The properties of the air at 100°C and 1 atm are the follows:

ρ = density = 0.9458 kg/m³

Cp = specific heat = 1009 J/kg K

Pr = 0.7111

The surface area of the plate is equal to:

Where

W = width of the plate = 0.2 m

L = length of the plate = 0.5 m

The average friction coefficient is equal to:

Where

F = drag force = 0.3 N

V = velocity of air flow = 100 m/s

The average heat transfer coefficient is equal to:

The surface temperature is:

Where

q = heat flux = 6100 W/m²

Tα = temperature of the air = 20°C = 293 K

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