Heat transfer thro Cardboard box 2

[BlueBull]

I wish to calc the heat transfer thro a cardboard box
consisting of a layer of outer liner 160 gram the fluting 160 gram then inner liner 160 gram. The distance from inner to outer liner is 6 mm. Are the standard heat transfer calculations adequate or are there unforeseen complications to consider

 

[gerhardl]

I have tried to imagine for what purpose.... but of course you could do this and come up with a teoretical figure.

For a practical purpose I believe that other variables than the cardboard box itself will influence on the result (whatever you want to obtain) : what you put in the box, corners and sealings, contents temperature, mass and form, other insulation in the box (airspace, paper, added insulation), surroundings (inhouse, outdoors, variable, constant, outer temperature history - time) etc.

At such it could be difficult to 'prove' that your figure is right.

What about the old engineering advice: Try it and see if it works? - Either with measuring miming your conditions, or as a practical application test?

 

[MintJulep]

Possibly the manufacturer already has a number.

Are you looking for a value for the material itself, or for a specific configuration made from the material?

 

[vpl]

Bluebull,

I think you ARE the manufacturer, right? I did some searching on some sites I had bookmarked and found the following two links, which both give a k value of 0.21 W/mK:

http://www.monachos.gr/en/resources/Thermo/conductivity.asp

http://www.physics.usyd.edu.au/teach_res/db/d0005e.htm

You could factor this into a standard conduction heat transfer equation. However, neither link gives a source for the information, nor any information about the makeup of the cardboard.

If you want a more precise measuremen, there is this link to a school lab project:

http://www.uow.edu.au/eng/phys/200labs/phys235/badcon.pdf

You might be able to run this experiment with your product and get a better answer.

Patricia Lougheed

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

 

[telecomguy]

You might look to the housing industry. A corrugated box resembles a studded wall pretty well. I'm sure they have the calcs all lined out for you somewhere.

<tg>

 

[btrueblood]

Holman's Heat Transfer (6th ed.) gives a value of 0.069 W/mK for "cardboard, corrugated" (no mention of paper weight or corrugation size). I don't have a value for paper alone, but wood runs the gamut from 0.055 W/m-K for balsa to 0.17 for oak and maple. I'd guess that 0.2 would be more valid for heavy paper stock, not a corrugated box wall.

 

[civilperson]

Easily measured.

 

[Tmoose]

And the convection resulting from airspaces much over 6 mm starts to become more and more important

 

[IRstuff]

The Mathcad E-book for "Building Thermal Analysis" lists corrugated cardboard at 0.06401 W/m-K, comparable to rock wool. This value is supposedly in the CRC handbook.

TTFN

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