Register to reply

Heat Transfer question.

by orangeklingon
Tags: heat, transfer
Share this thread:
Nov23-09, 10:43 AM
P: 1
1. The problem statement, all variables and given/known data
A 4-in.-OD pipe is used to transport liquid metals and will have an outside surface temperature of 1400 F under operating conditions. Insulation 6-in. thick and having a thermal conductivity expressed as k = 0.08(1-0.0003T) where k is in [Btu/hr*ft*F] and T is in [F], is applied to the outside surface of the pipe.
(a)What thickness of insulation would be required for the outside insulation temperature to be no higher than 300 F.
(b) What heat-flow rate will occur under these conditions?

2. Relevant equations
q/A = k dT/dx
A = 2*(pi)*r*L, Assume L is 1 ft.

3. The attempt at a solution
q/A dr = k dT
Integrate on both sides
q/2*(pi)( ln(r-pipe)-ln(r-insulation)) = 0.08(T-0.00015T^2)(evaluate from 1400 to 300)

Is this a Trick question? Do I assume that the insulation thickness is 6-in? Or is there a trick that I am missing?

I would like to have help on this by Wednesday November 25th by 4PM PST. Thanks
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
Phys.Org News Partner Science news on
'Smart material' chin strap harvests energy from chewing
King Richard III died painfully on battlefield
Capturing ancient Maya sites from both a rat's and a 'bat's eye view'
Nov24-09, 10:27 PM
P: 30
I may be able to help a bit..I had a question simmilar to this, but I've handed it in. I made and used a spreadsheet to solve it, not calculus.

With all of your given information, you can solve for the temperature of the fluid inside the pipe. (Is the thermal conductivity of the pipe neglected?)

Knowing the fluid temperature and the surface temperature, with the k value for each composite could you not solve for the thickness required to limit the temp. to 300?

Register to reply

Related Discussions
Question about heat transfer Classical Physics 10
Help please now heat transfer question Introductory Physics Homework 0
Question about heat transfer... Introductory Physics Homework 7
Heat transfer question. Classical Physics 3
Heat transfer Question Advanced Physics Homework 1