Expansion of Steel in the Sun 9

[steelbeam]

If a steel beam is setting in the sun when the ambient temperature may be 90 deg. F, could the steel have an actual internal temperature that is a much higher temperature, say 120 deg.?
I believe I read this somewhere but for the life a me I can't remember where.

 

[BAretired]

The following may be of some help:
thread172-169259

BA

 

[Lomarandil]

It really depends on other climate factors, but yes, it's possible.

For the bridges I work on (usually painted a light color and over large bodies of water), the steel temperature usually lags behind ambient temperature by several hours -- this often means that the steel never gets as warm as the peak ambient temperature, since by then the air has cooled back down.

I'd imagine that unpainted steel or steel not over bodies of water would be less forgiving.

 

[Triangled]

what an interesting question, to which, I am sure, there must be a scientific answer, but not from me....
anecdotal: I was told by contractors that in Palm Springs CA desert in the Summer, steel was too hot to handle past midmorning.... suggesting a significantly higher than ambient temperature

 

[JStephen]

Yes, things in the sun will oftentimes be hotter than the surrounding air. Typical for asphalt streets, car seats, etc. There's a scientific "solution", but not just some single number- that's a combined radiation/convection heat transfer problem and the simplest solution is to just go measure the temperature of whatever it is.

 

[thaidavid40]

Just try putting you hand on top of a car parked in the summer sun for a few hours! That will convince you of the difference in the steel temperature versus the air temperature. You can literally fry an egg on some darker colored cars. Unpainted steel, or steel painted a heat-absorptive color, will get significantly hotter by far than the surrounding air.

Thaidavid

 

[kingnero]

Railroad track is another example. Colder atnight and hotter during sunny days, both by over 20°C than ambient temp.

 

[3DDave]

Steel can seem hotter because of thermal conductivity. Which is why the old-fashioned steel seat-belt buckles would practically fry you, but the fabric belts would not. Given that the average heat from sunshine is 1kW/sq meter, then to stabilize the steel has to be hot enough to reject a similar amount of heat. 120F seems about right.

 

[dhengr]

And, that’s why they decided to keep seat-belt buckles under one square meter in size.

 

[IRstuff]

The inverse is true as well; it's possible to get below freezing on surfaces at night, even with ambient temperature above freezing. It's the radiative process that produces the difference in both cases. Assuming a 50% reflectivity/emissivity and 7.5W/m^2-K, the delta temperature above ambient would be about 45C, from a very simplistic flat surface. YMMV

TTFN
I can do absolutely anything. I'm an expert!
faq731-376 forum1529

 

[fel3]

In the early 1980s I designed a 3 million gallon welded steel water storage tank in Westlake Village, CA, which is between Thousand Oaks and the San Fernando Valley. I was then assigned to do the field inspections. One of my tools was a magnetic thermometer for measuring the temperature of the steel during painting. A few days before the painters arrived, I started measuring steel temperatures around the tank at different times of the day to develop a rough idea of what we would be dealing with (I also marked the ringwall with a crayon so I could see how much the tank expanded from morning to mid-day, but that was for my own amusement).

As I recall, on one 105°F day, the steel temperature in the Sun at about 3 p.m. was around 180°F. On the north side of the tank, the shaded steel was around 100°F.

Fred

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[gravityandinertia]

This may be relevant:

Arizona Egg Fry Video

 

[gravityandinertia]

People, and even Engineer's forget there are 3 methods of heat transfer, conduction, convection and radiation. For convection, what most people think of when thinking of things heating up outside, you won't have steel getting hotter than the ambient, unless the ambient starts cooling down, and the steel cools slower than the air. However, heat transfer in the form of solar radiation to the steel can make steel temperatures rise significantly beyond the ambient air temperature. So anywhere the sun is intense, you will have this scenario, for this reason, you will find this scenario commonly in the western/southwestern portion of the United States.