Temperature-Energy conversion

kojikun · Post by **kojikun** » 2003-04-27 07:28pm

Suppose I need to convert degrees to joules for a given material. What do I need to know and what equation(s) would I use?

NapoleonGH · Post by **NapoleonGH** » 2003-04-27 07:35pm

Look up what the specific heat of the substance that has the given temperature is. Then multiply that number by the temperature, and you should get the number of energy units (depends on what system you are using obviously, you could get calories or joules, just make sure you have all your units matching up otherwise you'll have a problem like NASA did with that mars ship that crashed cuz they were using feet instead of meters)

kojikun · Post by **kojikun** » 2003-04-27 08:14pm

feet instead of metres huh? NASA fucked that one up. haha

thanks for the info

NapoleonGH · Post by **NapoleonGH** » 2003-04-27 08:18pm

no prob, out of curiousity, what substance are you trying to figure this out for?

kojikun · Post by **kojikun** » 2003-04-27 11:27pm

i WAS looking at tungsten or rhenium, but found that they have absurdly small specific heats. lithium, however, has a nice specific heat, about 3KJ/kg or sommat like that.

oh, also, the purpose was to determine an ablative material that could be used in a pulse detonation nuclear rocket. figured that you'd need a few million kilos of material per detonation of even the smallest possible nuclear bomb (0.01 kiloton davie crocket)

Slartibartfast · Post by **Slartibartfast** » 2003-04-28 01:59am

NapoleonGH wrote:Look up what the specific heat of the substance that has the given temperature is. Then multiply that number by the temperature, and you should get the number of energy units (depends on what system you are using obviously, you could get calories or joules, just make sure you have all your units matching up otherwise you'll have a problem like NASA did with that mars ship that crashed cuz they were using feet instead of meters)

I think it also depends on the change of state, like you can have water boiling, and the energy in it isn't the same (it's still 100 degrees, but the closer they are to gaseous state, the more energy it's supposed to have, or something)

NapoleonGH · Post by **NapoleonGH** » 2003-04-28 09:17pm

yes slarti, Specific Heat is different depending on state, and you also have to include heat of vaporization/fusion (vaporization = liquid to gas and vice versa, fusion = liquid to solid and vice versa)