# Temperature of a body exposed to sunlight

1. Nov 28, 2011

### jc.int

hello,
If I have a black painted aluminium exposed to sunlight (being it and the atmosfere at 27ºC), and I have the total solar radiation it is exposed to (lets say 1 ° KW-hr/m²), how can I know the evolution of its temperature?
(if there is any free simulator on the internet I would be glad if someone could give it, but I haven't found any).

Thank you,
Jaimie

2. Nov 28, 2011

### technician

If you only consider heat loss by radiation then I would say that the blackened Aluminium would reach an equilibrium temperature when it is radiating 1kW/m^2
Then use Stefan's law
E = σT^4 to find T (in Kelvin)

3. Nov 28, 2011

### dacruick

Hi Jaimie,

I don't understand this unit here below. What you will need to do is find the cross sectional area of your aluminum bucket and use that to find the energy per unit time being absorbed by the bucket.

The other answer given to you will be very approximate because the entire bucket will be radiating heat, while only the side facing the sun will be acquiring heat.

You have a few assumptions to make.

4. Dec 1, 2011

### jc.int

I mean that the solar energy received in one m2 in 1hour is 1 ° KW (metric units for solar energy radiatio, see http://www.raws.dri.edu/cgi-bin/rawMAIN.pl?nmXHAC , equivalent to the Langley, ºly). What I'd like to know what is the relation between the painting absorbion, aluminum heat capacity, etc

Thank you,
Jaimie

5. Dec 1, 2011

### dacruick

I was confused previously because your first unit was not a rate.

I think it would help for you to write down a list of variables that you have to consider. That way you can decide which ones are "negligible" and which ones you'd like to make assumptions for. I assure you that there are more variables than absorption and heat capacity.