3. (8.30) Air at p=1 atm enters a thin-walled long tube (D = 5mm, L=2m) at an inlet temperature of Tm1=100°C. A constant heat flux is applied to the air from the tube surface. The air mass flow rate is mdot=135x10-6 kg/s. a. if the tube surface temperature at the exit Ts,。 = 160°C, determine the heat rate entering the tube. Evaluate properties at T=400K. (Ans: q=7.16W) b. If the tube length of part (a) were reduced to L=0.2m, how would flow conditions at the tube exit be affected? Would the value of the heat transfer coefficient at the tube exit be greater than, equal to, or smaller than the heat transfer coefficient for part (a)? c. If the flow rate of part (a) were increased by a factor of 10, would there be a difference in flow conditions at the tube exit? Would the value of the heat transfer coefficient at the tube exit be greater than, equal to, or smaller than the heat transfer coefficient for part (a)?

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN:9781305387102
Author:Kreith, Frank; Manglik, Raj M.
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Chapter7: Forced Convection Inside Tubes And Ducts
Section: Chapter Questions
Problem 7.7P
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Please help. I am not sure how to approach this problem. This problem involves heat transfer and internal flow within a pipe. Thank you.

3. (8.30) Air at p=1 atm enters a thin-walled long tube (D = 5mm, L=2m) at an inlet
temperature of Tm1=100°C. A constant heat flux is applied to the air from the tube
surface. The air mass flow rate is mdot=135x10-6 kg/s.
a. if the tube surface temperature at the exit Ts,。 = 160°C, determine the heat rate
entering the tube. Evaluate properties at T=400K. (Ans: q=7.16W)
b. If the tube length of part (a) were reduced to L=0.2m, how would flow conditions
at the tube exit be affected? Would the value of the heat transfer coefficient at the
tube exit be greater than, equal to, or smaller than the heat transfer coefficient for
part (a)?
c. If the flow rate of part (a) were increased by a factor of 10, would there be a
difference in flow conditions at the tube exit? Would the value of the heat transfer
coefficient at the tube exit be greater than, equal to, or smaller than the heat
transfer coefficient for part (a)?
Transcribed Image Text:3. (8.30) Air at p=1 atm enters a thin-walled long tube (D = 5mm, L=2m) at an inlet temperature of Tm1=100°C. A constant heat flux is applied to the air from the tube surface. The air mass flow rate is mdot=135x10-6 kg/s. a. if the tube surface temperature at the exit Ts,。 = 160°C, determine the heat rate entering the tube. Evaluate properties at T=400K. (Ans: q=7.16W) b. If the tube length of part (a) were reduced to L=0.2m, how would flow conditions at the tube exit be affected? Would the value of the heat transfer coefficient at the tube exit be greater than, equal to, or smaller than the heat transfer coefficient for part (a)? c. If the flow rate of part (a) were increased by a factor of 10, would there be a difference in flow conditions at the tube exit? Would the value of the heat transfer coefficient at the tube exit be greater than, equal to, or smaller than the heat transfer coefficient for part (a)?
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