Effects of geometry on heat exchanger 2

[josephn16]

I have a good friend (who is not very computer literate) who is a Mechanical Engineer in a Forging Plant. He needs to cool steel in a tank of either a polymer solution or just water, and he asked me last night about the effects of the shape of the piece he is attempting to cool. The cooling rate is the key factor in some impact tests they have recently failed, and they are thinking of upgrading the heat exchange system to allow for a higher cooling rate.

I am sure that there is a point when it is practical to consider geometry (after all, 100 lbs of steel wire would cool faster than a 100lb sphere,) but I do not remember what equations are used to consider goemetry. I seem to remember something about using the shortest distance from the surface to the center of the mass???

I hope my question is clear, any help would be great.

 

[abeltio]

There is extensive bibliography on the subject of heat transfer from simple shapes.
Heat Transfer by Jakobs (2 volumes) and Heat Transfer by Addams are two classic references...
HTH
Saludos.
a.

 

[poetix99]

You should, in my opinion, try to find some references that are specific to the steel industry, or at least the metals industries.

The properties of the steel will depend not only upon the cooling rate, but also the initial "ingot" temperature from which they have been cooled (quenched). Sure, a wire will cool faster than a typical ingot shape, but it will have cooled at a somewhat uncontrolled rate beforehand.

If there is a "reheating" furnace available, that will help, of course. The point still stands, however: steel is in (relatively) bulky initial shapes for control of the starting temperature of a quench, not for maximization of cooling rates.

Consider liquid sprays instead of passive baths; this might help to increase the cooling rate.