Heat Exchanger Insulation

[doma1516]

Hey,

I am designing a box with a set of four series connected heat exchangers. I am trying to determine the thickness of the insulation required for this box. I know the maximum temperature of fluid entering the heat exchangers and also the temperature of cold fluid. I know the coefficient of Heat Transfer for the insulation. I just cant figure out how to determine the thickness of insulation. How do i calculate the rate of heat generation inside the heat exchanger box. Can anyone help./
Thanks in advance

 

[vpl]

It really depends on what's on the outside of the box and why you're wanting to insulate it.

To paraphrase MintJulep's response in thread391-219156 : The equations governing heat transfer can be found in any heat transfer text.

If you don't have one on your bookshelf a perfectly fine one may be downloaded (legally and free) here:

http://web.mit.edu/lienhard/

http://www/ahtt.html

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[KiwiMace]

If we were to statistically analyse the responses at Eng-tips, the biggest winner would have have to be the request for more information.

Your question does not provide enough information to begin to provide an intelligent answer.

You are being asked to read a textbook, not so much to go do it yourself, but to understand the type of problem sufficiently well enough to be able to ask a question that can be answered.

 

[doma1516]

Hey
Thanks for the reply guys.

Its actually a heat exchanger which is covered with insulation and kept in a stainless steel enclosure. The maximum temperature of the hot fluid entering the heat exchanger is 500 degrees c. The box is kept open to the atmosphere so the maximum outside temperature cannot be more than 50 degrees c. I applied the heat conduction across a plane wall equation taking 500 and 50 as the temps but this is obviously not the right way to work it out. I was wondering if there was anyway for me to determine the Heat lost by heat exchanger to the inside of the box and the temperature it would create within the box.

 

[pmover]

doma1516 . . .

i second KiwiMace comments . . . insufficient info has been provided by you . . . in addition to VPL comments, have you have any formal education in heat transfer?

what makes you think planar is "not the right way to work it out"?

how about the physical shape of the exchanger - square, cylindrical, etc. planar heat transfer is different from cylindrical or spherical . . .

we can only assist you and not do your work as we assume you have read and understood the policies of this site and the engineering profession as a whole.

so a little more info about your knowledge/background of heat transfer and the "problem" you have, would be helpful to get you a solution.

good luck!
-pmover

 

[vpl]

doma1516

A few more questions:

Is the 50°C ambient temperature outside the box or inside the box?

Is the box going to be exposed to external sources of heat (i.e., will it be placed in sunlight)?

Is the box insulated or is it the heat exchangers being insulated?

If it's the heat exchangers, will the insulation be uniform on all parts (and on everything between them)?

Is each heat exchanger going to have 500°C fluid entering it?

Is the piping for the hot fluid entering each heat exchanger also going to be insulated?

Finally, if you don't like the answer (which I would take as the amount of insulation being more than you expected), then it may mean you need to get a different type of insulation.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[doma1516]

hey,
Thanks for the reply.
I know i have been given less information but i have to take personal steps and create something out of it.

I think i didn't put all my information to you guys. Let me try it once again.

I have a heat exchanger arrangement (rectangular). The hot fluid entering the heat exchanger is at 500 C.
The heat exchanger is directly covered with a insulation similar to glass wool with a Coefficient of heat transfer equivalent to 0.08 W/m-K. Also to support this assembly there is a stainless steel enclosure.
This set up is mainly used in Axillary power units, and will be kept in atmosphere and the maximum temp at the outside of the stainless steel box should not exceed 50 C.

What my main aim is to determine the thickness of the insulation. I used the steady state heat conduction equation to determine the thickness, would that be the right way to do this or is there something i am missing out.

 

[vpl]

I would use the standard steady state conduction equation. Don't forget to take into account any air gap between the insulation and the steel enclosure or the steel enclosure itself.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.