Refer to Problem 4.91. Use MATLAB to obtain the transfer functions Θ 1 s / T 2 s and Θ 2 s / T 2 s for the values I 1 = 10 , I 2 = 20 , and k 1 = k 2 = k 3 = 60 . Compare your answers with those found in part (b) of Problem 4.91.
Refer to Problem 4.91. Use MATLAB to obtain the transfer functions Θ 1 s / T 2 s and Θ 2 s / T 2 s for the values I 1 = 10 , I 2 = 20 , and k 1 = k 2 = k 3 = 60 . Compare your answers with those found in part (b) of Problem 4.91.
Refer to Problem 4.91. Use MATLAB to obtain the transfer functions
Θ
1
s
/
T
2
s
and
Θ
2
s
/
T
2
s
for the values
I
1
=
10
,
I
2
=
20
, and
k
1
=
k
2
=
k
3
=
60
. Compare your answers with those found in part (b) of Problem 4.91.
A group of 23 power transistors, dissipating 2 W each, are to be cooled by attaching them to a black-anodized square aluminum plate and mounting the plate on the wall of a room at 30°C. The emissivity of the transistor and the plate surfaces is 0.9. Assuming the heat transfer from the back side of the plate to be negligible and the temperature of the surrounding surfaces to be the same as the air temperature of the room, determine the length of the square plate if the average surface temperature of the plate is not to exceed 50°C. Start the iteration process with an initial guess of the size of the plate as 43 cm.
The properties of air at 1 atm and the film temperature of (Ts + T)/2 = (50 + 30)/2 = 40°C are k = 0.02662 W/m·°C, ν = 1.702 × 10–5 m2 /s, Pr = 0.7255, and β = 0.003195 K–1.
Multiple Choice
0.473 m
0.284 m
0.513 m
0.671 m
A 40-cm-diameter, 127-cm-high cylindrical hot water tank is located in the bathroom of a house maintained at 20°C. The surface
temperature of the tank is measured to be 44°C and its emissivity is 0.4. Taking the surrounding surface temperature to be also 20°C,
determine the rate of heat loss from all surfaces of the tank by natural convection and radiation.
The properties of air at 32°C are k=0.02603 W/m-K, v=1.627 x 10-5 m²/s, Pr = 0.7276, and ẞ = 0.003279 K-1
The rate of heat loss from all surfaces of the tank by natural convection is
The rate of heat loss from all surfaces of the tank by radiation is
W.
W.
A 2.5-m-long thin vertical plate is subjected to uniform heat flux on one side, while the other side is exposed to cool air at 5°C. The
plate surface has an emissivity of 0.73, and its midpoint temperature is 55°C. Determine the heat flux subjected on the plate surface.
Uniform
heat flux
-Plate, € = 0.73
Cool air
5°C
7
TSUIT
Given: The properties of water at Tf,c= 30°C.
k=0.02588 W/m.K,
v=1.608 x 10-5 m²/s
Pr = 0.7282
The heat flux subjected on the plate surface is
W/m²
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