conduction from under water

[cdxx139]

Looking to do a heat loss through the steel hull of a dry dock. Half is under seawater. The water temp is 50 degF and the OA is 25 degF and indoor conditions being 60degF. SO I did a typical UAdT equation for both above water and underwater sections. U of steel being 1.2 and dT for above water being 35=(60-25) and dT for below water being 10=(60-50).

I was told my heat required in the hull is over sized from what they have in an older dry dock of comparable size. I was told I should be taking more of a credit for the portion above water, because of the portion below water.

So I went back to basics and opened my thermo book to Fourier's Law, but the k value has to do with the steel hull, not the fluid difference?

I am still looking but could use some assurance if its good enough or assistance if I am calculating incorrectly.

knowledge is power

 

[willard3]

Probably should be posted in "Heat Transfer & Thermodynam9ics" section for better answers.

 

[317069]

Did you discuss with the person who told you your calculation is oversized to know why?
I didn't understand exactly what did you mean by (but the k value has to do with the steel hull, not the fluid difference?)

 

[Compositepro]

Most of the resistance to heat flow is due to the interfaces between the steel and the water or the air, and not to the conductivity of steel. This is represented by the convective heat transfer coefficients, not the coefficient of thermal conductivity.

Say, for example, there were no steel plate. Would the heat transfer between water and air become infinite? Of course not.

 

[cdxx139]

Took your advice and cross posted to thermo.

I was treating it as steady stae since the dry dock is not moving, but since the waves are, you are saying I should take into effect convection?

knowledge is power

 

[Compositepro]

Double posting is against site rules. You now have two separate conversations going. If you do ask a question in two different forums you should ask all answers to be posted in only one of them.

 

[IRstuff]

I suggest that the OP red flag this thread altogether and stick with the thread in the heat transfer forum. You could possibly copy your OP and paste that into the other thread.

TTFN
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Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com:

http://www.engineering.com/AskForum/aff/32.aspx

 

[cdxx139]

I thought you can double post provided it was communicated and everyone was aware, my bad. I wasn't trying to deceive.

I will continue this in the thermo forum, if anybody is interested.

http://www.eng-tips.com/viewthread.cfm?qid=388527

knowledge is power