Q1: Air enters a 7m long section of a rectangular duct of cross section 15 cm x 20 cm at 50°C at an average velocity of 7 m/s. If the walls of the duct are maintained at 10 C, determine (a) the outlet temperature of the air, (b) the rate of heat transfer from the air. Air properties from tables: p-1.127 kg/m' k=0.02662 W/m. C D 1.702 x10 m/is C, -1007 J/kg. C Pr 0.7255 Answer: (a): Te 34.2 °C, (b): Q' = 3776 W Hint: 1- Use the Logarithmic mean temperature difference relations. If Reer 2300, in pipes and ducts, the flow is turbulent. 2- T-10°C Air duet 15 em x 20 em Air L-7 m 50°C 7 m/s

Q1: Air enters a 7m long section of a rectangular duct of cross section 15 cm x 20 cm at 50°C at an average velocity of 7 m/s. If the walls of the duct are maintained at 10 C, determine (a) the outlet temperature of the air, (b) the rate of heat transfer from the air. Air properties from tables: p-1.127 kg/m' k=0.02662 W/m. C D 1.702 x10 m/is C, -1007 J/kg. C Pr 0.7255 Answer: (a): Te 34.2 °C, (b): Q' = 3776 W Hint: 1- Use the Logarithmic mean temperature difference relations. If Reer 2300, in pipes and ducts, the flow is turbulent. 2- T-10°C Air duet 15 em x 20 em Air L-7 m 50°C 7 m/s

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

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Question

Q1: Air enters a 7m long section of a rectangular duct of cross section 15 cm x 20 cm at 50°C
at an average velocity of 7 m/s. If the walls of the duct are maintained at 10 C, determine (a)
the outlet temperature of the air, (b) the rate of heat transfer from the air.
Air properties from tables:
p=1.127 kg/m'
C,-1007 J/kg. C
k 0.02662 W/m.°C
Pr 0.7255
D=1.702x10 m'/s
Answer: (a): Te 34.2 °C,
(b): Q' 3776 W
Hint: 1- Use the Logarithmic mean temperature difference relations.
If Reer 2300, in pipes and ducts, the flow is turbulent.
T-10°C
Air duet
15 em x 20 em
Air
50°C
7 m/s
L-7m

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