convection coefficient (h) of the wind 3

[johnT05]

Hi
I'm working on a heated railway to avoid accumulation of ice and snow.
My intention is to simulate the heat transfer with SolidWork simulation
To do it I need the heat transfer coefficient (h) of the wind from 0km to 100km.
My question is how to calculate the heat transfer coefficient (h) of the wind on a 50km long railway. Can I use simple correlations?
Thanks for your help.

 

[IRstuff]

There are lots of heat transfer texts that allow you to calculate the heat transfer coefficient, including free ones:

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

http://www/ahtt.html

Nonetheless, you will be trodding some old ground. SAE AIR 1168-4 Ice, Rain, Fog, and Frost Protection covers the subject of maintaining ice-free conditions on surfaces, albeit, primarily for aircraft surfaces. Table 3F-4, in particular, gives heating loads required to maintain ice-free windshields --> 2.44 W/in^2 for 100 kt cruise speed

TTFN

FAQ731-376

 

[berkshire]

IR stuff,
I have given you a star for answering my question before I even asked it.
I am working on an aircraft engine cowling and the associated airflow for heat rejection. I was googling heat transfer when this popped up.
Thank you.
B.E.

 

[IRstuff]

Glad to be of help ;-)

Just note that that AIR 1168 is actually a 14-volume SAE Aerospace Applied Thermodynamics Manual. Volume 3 Aerothermodynamic Systems Engineering and Design might also be relevant to your efforts.

TTFN

FAQ731-376

 

[corus]

The heat input of 2.44 W/in^2 seems a mixture of imperial and metric units so I'd check the value. This isn't a heat transfer coefficient of course. The value I've used for wind has been about 50 W/m^2 C but I forget the reference for that. This site

http://zomeworks.com/files/double-play/FrankdeWinter/FdW_ExternalHeatTransfer.pdf

gives a relationship of h=5.7+3.8V in SI units. Using 12 m/s (26 mph), as being a strong wind, gives you 50 W/m^2 C, and of course 5.7 W/m^s C for still wind (or natural convection). You give a wind of 100km, which of course isn't a velocity at all but a distance so doesn't have much meaning.

ex-corus (semi-detached)

 

[IRstuff]

The value quoted was, as explained above, the heat load generated by any de-icing heaters to maintain ice-free conditions. This is the end result of any convective and evaporative cooling by the airstream.

TTFN

FAQ731-376

 

[ione]

This is a problem of forced convention. There are several known correlations developed over years (in the attachment you can find some of these in paragraph 5 for flat surface).

Maybe also the calculator in the link below could be of some help

http://www.thermal-wizard.com/tmwiz/default.htm

 

[johnT05]

Thanks ione for this good link