Forced air at 250C and 10 m/s is used to cool electronic elements mounted on a circuit board. Consider a chip of length 4 mm and width 4 mm located 120 mm from the leading edge. Because the board surface is irregular, the flow is disturbed and the appropriate convection correlation is of the form N u x = 0.04 Re x 0.85 Pr 0.33 . Estimate the surface temperature of the chip, T s , if its heat dissipation rate is 30 mW.
Forced air at 250C and 10 m/s is used to cool electronic elements mounted on a circuit board. Consider a chip of length 4 mm and width 4 mm located 120 mm from the leading edge. Because the board surface is irregular, the flow is disturbed and the appropriate convection correlation is of the form N u x = 0.04 Re x 0.85 Pr 0.33 . Estimate the surface temperature of the chip, T s , if its heat dissipation rate is 30 mW.
Solution Summary: The author explains that the value of the Surface temperature T_q is 44.023°.
Forced air at 250C and 10 m/s is used to cool electronic elements mounted on a circuit board. Consider a chip of length 4 mm and width 4 mm located 120 mm from the leading edge. Because the board surface is irregular, the flow is disturbed and the appropriate convection correlation is of the form
N
u
x
=
0.04
Re
x
0.85
Pr
0.33
.
Estimate the surface temperature of the chip,
T
s
,
if its heat dissipation rate is 30 mW.
Air at atmospheric pressure and a temperature of 25 degrees C is in parallel flow at a velocity of 5 m/s over a 1-m-long flat plate that is heated from below with a uniform heat flux of 1250 W/m2 . Assume the flow is fully turbulent over the length of the plate. Take ν = 18.76 × 10−6 m2/s, k = 0.0284 W/m·K and Pr =0.703. (a) Calculate the plate surface temperature, Ts(L), and the local convection coefficient, hx(L), at the trailing edge, x = L. (b) Calculate the average temperature of the plate surface.
Air at -10° C flows over a smooth sharp-edged, almost flat aerodynamics surface that is held at 10°C, at a speed of 120 km/hr . What is the greatest length the plate can be if the flow is to remain laminar over the entire length of the plate? What would be the average film coefficient be of that plate and what is the heat flux? What are the heights of the fluid and thermal boundary layers at the end of that length? Use Re = 350,000 for the critical Reynolds number.
Air at standard pressure flows across a flat plate at 3m/s. The temperature surface is 50oC and the surrounding temperature is 20o Consider a point 1m away from the leading edge of the plate. See Table A-15 in Appendix 1 for properties of air.
Determine the Reynold’s number and Prandtl number for this flow at the location described above.
Determine the local flow boundary layer thickness.
Determine the local thermal boundary layer thickness for this flow.
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