9. Fin efficiency is defined as: tanh (mL) (hP/k Ac)1/2 (heat transfer with fin) / (heat transfer without fin) (actual heat transfer through fin) / (heat transfer assuming all fin is at T = Tb) (Tx=L-Tf)/(Tb-Tf) 10. For an infinite fin, the temperature distribution is given by: (T-Tf)/(Tb-Tf)=e-mx. The heat flow through the fin is therefore given by: k (Tb-Tf)/L zero, because the fin is infinite infinite because the fin is infinite (Tb-Tf) (h P/k Ac)1/2 (Tb – Tf) (h_P/ k Ac)1/2 tanh (mL) 11. The Biot number, Bi, is defined as: • Bi=hk/L • Bi=hL/k • Bi= k/LH • Bi=qL/k • Bi=p UL/k 12. For a plate of length L, thickness, t, and width, W, subjected to convection on the two faces of area L x W. What is the correct length scale for use in the Biot number? L . W . t/2 • L/2 13. If Bi << 1, then this implies: heat transfer is negligible the surface is insulated conduction is time dependent temperature variations within the solid are negligible temperature variations within the solid are significant
9. Fin efficiency is defined as: tanh (mL) (hP/k Ac)1/2 (heat transfer with fin) / (heat transfer without fin) (actual heat transfer through fin) / (heat transfer assuming all fin is at T = Tb) (Tx=L-Tf)/(Tb-Tf) 10. For an infinite fin, the temperature distribution is given by: (T-Tf)/(Tb-Tf)=e-mx. The heat flow through the fin is therefore given by: k (Tb-Tf)/L zero, because the fin is infinite infinite because the fin is infinite (Tb-Tf) (h P/k Ac)1/2 (Tb – Tf) (h_P/ k Ac)1/2 tanh (mL) 11. The Biot number, Bi, is defined as: • Bi=hk/L • Bi=hL/k • Bi= k/LH • Bi=qL/k • Bi=p UL/k 12. For a plate of length L, thickness, t, and width, W, subjected to convection on the two faces of area L x W. What is the correct length scale for use in the Biot number? L . W . t/2 • L/2 13. If Bi << 1, then this implies: heat transfer is negligible the surface is insulated conduction is time dependent temperature variations within the solid are negligible temperature variations within the solid are significant
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
Related questions
Question

Transcribed Image Text:Conduction
Heat Transfer
X
material (a)
material (b)
.
both (a) and (b) have the same thermal conductivity
the temperature distribution is independent of thermal conductivity
it's not that simple
9. Fin efficiency is defined as:
• tanh (mL)
(hP/k Ac)1/2
(heat transfer with fin) / (heat transfer without fin)
(actual heat transfer through fin) / (heat transfer assuming all fin is at T = Tb)
(Tx=L-Tf)/(Tb-Tf)
10. For an infinite fin, the temperature distribution is given by: (T-Tf)/(Tb-Tf)= e-mx. The
heat flow through the fin is therefore given by:
k (Tb-Tf)/L
●
zero, because the fin is infinite
●
infinite because the fin is infinite
● (Tb-Tf) (hP/k Ac)1/2
●
(Tb – Tf) (h P / k Ac)1/2 tanh (mL)
11. The Biot number, Bi, is defined as:
• Bi=hk/L
• Bi=hL/k
• Bi= k/LH
• Bi=qL/k
• Bi=p UL/k
12. For a plate of length L, thickness, t, and width, W, subjected to convection on the two faces
of area L x W. What is the correct length scale for use in the Biot number?
. L
● W
● t
• t/2
• L/2
13. If Bi << 1, then this implies:
• heat transfer is negligible
●
the surface is insulated
conduction is time dependent
temperature variations within the solid are negligible
.
temperature variations within the solid are significant
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