A pin fin of uniform cross-sectional area is fabricated of an aluminum alloy (k = 160W m-1 K-1 ). The fin diameter is D = 4 mm,
and the fin is exposed to convective conditions characterized by h = 220W m-2 K-1 . It is reported that the fin efficiency is ?f = 0.65. Account for convection heat transfer at the fin tip.
Questions: (a) What is the length of the fin, L?
(b) What is the fin effectiveness ?f?
Questions: (a) What is the length of the fin, L?
(b) What is the fin effectiveness ?f?
1 answer:
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Answer:
The answer is given in the explanation.
Explanation:
The circuit is as indicated in the attached figure.
From the analytical description the zener voltage is given as
Here
Vzo is the voltage at which the slope of 1/rz intersects the voltage axis it is equal to knee voltage.
The equivalent model is shown in the attached figure.
From the above equation, Vzo is calculated as
Here Vz is given as 7.5 V
Iz is given as 10 mA
rz is given as 30 Ω
Thus the Vzo is given as
The value of I_L is given as 5 mA
Now the expression of current is as
Now the resistance is calculated as
So the value of resistance is 186.66 Ω.
Considering the supply voltage is increased by 10%
V is 10-10%*10=10+1=11 so the
Considering the supply voltage is decreased by 10%
V is 10-10%*10=10-1=9 so the
Now if the supply voltage is 10% high and the value of Load is removed i.e I=Iz only which is 10mA
so
Now the largest load current thus that the supply voltage is 10% low and the current of zener is knee current thus
The load voltage is 7.485 V
