Energy required for temperature raise - temperature-dependent specific heat capacity


by davidray
Tags: heat capacity, moles, thermal physics
davidray
davidray is offline
#1
Oct17-11, 06:09 AM
P: 7
Any help on this quistion would be greatly appreciated. I have no idea ho to answere it, and can't find anything in my nothes or books anywhere.

The temperature-dependent molar specific heat capacity at constant pressure of many substances is given by: c =a+2bT−cT^−2

For magnesium, the numerical values of the constants are: a=25.7, b=3.13x10^-3, c=3.27x10^5

where c has units J/Kxmol

Calculate the energy required to raise the temperature of 15g of Megnesium from 30 C to 300 C.

I have tried using the formula to qenerate a specific heat capacity for each temperature, but just seem to get crazy numbers that don't make any sense!

Thanks for the help!
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edgepflow
edgepflow is offline
#2
Oct17-11, 02:47 PM
P: 688
You can find the average value of the specific heat over the temperature range from:

C_avg = [itex]\frac{1}{Tf-To}[/itex][itex]\int[/itex][itex]\frac{To}{Tf}[/itex]C(T) dt

Then compute the energy from:

E = m C_avg (Tf - Ti)
apatel
apatel is offline
#3
Oct17-11, 11:56 PM
P: 2
any help for the following qestion will be appriciated

15mm thick concrete slab have an electric underfloor heater running in off peak time and release storage heat during day time then how much time its to reduce temp. from 23.5 at6:00am to 21 degree and with the variable outside temp. during day.outside temp is 8 degree and reuire temp. 19 at 6:00am and heat transfer output is 41.62w/m2

and how much time its to increse the temp during running off peak time

apatel
apatel is offline
#4
Oct17-11, 11:58 PM
P: 2

Energy required for temperature raise - temperature-dependent specific heat capacity


Quote Quote by apatel View Post
any help for the following qestion will be appriciated

15mm thick concrete slab have an electric underfloor heater running in off peak time and release storage heat during day time then how much time its to reduce temp. from 23.5 at6:00am to 21 degree and with the variable outside temp. during day.outside temp is 8 degree and reuire temp. 19 at 6:00am and heat transfer output is 41.62w/m2

and how much time its to increse the temp during running off peak time
reply with the equation


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