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Air at 20oC flows over a flat plate of dimensions 50 cm x 25 cm. If the average heat transfer coefficient is 250 W/m2K, determine the steady rate of heat transfer from one side of the plate to air when the plate is maintained at 40oC.

Respuesta :

Assumptions:

  • Steady state.
  • Heat transfer by convection.
  • The temperature on the surface of the plate is constant and uniform.

Explanation:

According to the attached image, the local heat flux over a flat plate can be expressed as follows,

[tex]Q = (T_{s} - T_{\infty}) \ A_s \int\limit_{A_{s}} {h} \, dA_{s}[/tex]

Where:

[tex]Q : Local \ Heat \ Flux [W]\\T_{s} : Temperature \ on \ the \ surface \ of \ the \ plate \ [K]\\T_{\infty} : Temperature \ of \ the \ room \ [K]\\h : Convective coefficient [\frac{W}{m^2 K} ]\\A_{s} : Area \ of \ the \ plate [m^{2}][/tex]

Consider an average convection coefficient,

[tex]Q = \overline{h} \ A_{s} \ (T_s -T_{\infty})[/tex]

Answer:

Then, replacing all the values in the previous expression,

[tex]Q = (250 \frac{W}{m^2 K} )(0.5m)(0.25m)(313.5K - 293.15K)\\Q= 625W[/tex]

Ver imagen jauriberamirez