Me 341 A
Discussion Problem
Set-8
Problem 1
A flat plate of width 1 m is maintained at a uniform surface temperature of Ts =
150°C by using independently controlled, heat-generating rectangular modules of
thickness a = 10 mm and length b = 50 mm. Each module is insulated from its
neighbours, as well as on its back side. Atmospheric air at 250C flows over the
plate at a velocity of 30 rn/s. The thermo physical properties of the module are k
= 5.2 W/m ·K, Cp = 320 J/kg ·K, and ρ = 2300 kg/m 3
(a) Find the required power generation, q (W/m2 in a module positioned at a
distance 700 mm from the leading edge.
(b) Find the maximum temperature Tmax in the heat generating module.
Problem 2
Consider a rectangular fin that is used to cool a motorcycle engine. The fin is 0.15 m long
and at a temperature of 250°C, while the motorcycle is moving at 80 km/h in air at 27°C.
The air is in parallel flow over both surfaces of the fin, and turbulent flow conditions may be
assumed to exist throughout.
a)What is the rate of heat removal per unit width of the fin?
Problem 3
One hundred electrical components, each dissipating 25 W, are attached to one
surface of a square (0.2 m X 0.2 m ) copper plate, and all the dissipated energy is
transferred to water in parallel flow over the opposite surface.
A protuberance at the leading edge of the plate acts to trip the boundary layer,
and the plate itself may be assumed to be isothermal. The water velocity and temperature are u∞= 2m/s and T∞= l7°C, and the water's thermo physical properties may be
approximated as v = 0.96 X 10-6 m2/s, k = 0.620 W/m ·K, and Pr = 5.2.
Problem 3
(a) What is the temperature of the copper plate?
(b) If each component has a plate contact surface area of I cm2 and the corresponding
contact resistance is 2 X 10-4 m2 • K/W, what is the component temperature? Neglect
the temperature variation across the thickness of the copper plate.
Problem 3
Thank you