This is a pretty easy calculation, however I've been out of school too long and my last two jobs had very little thermo, or even math required.
If I know my mass, Cp, Mp and Ambient I can calculate the number joules required to make the mass of metal reach the Mp. How do I figure time?
Joules are convertable to watthour, I know the wattage of the heater, so then do I just divide the two?
IE: 20Kg, 0.167 J/gm*C, 138C, ambient 20C
Res: 394120J
Converting gives: 109.5 watthour
The heat required to get over the heat of fusion (Hf) is given by:
mass*Hf = 982000J
and conversion gives: 272.78 watthour
So the total required heat to melt 20kg of metal is 382.28 W*hrs
Do I just divide by the wattage? (I know that this is assuming 100% effective transfer of heat, but some assumption is always necessary.)
So a 1000watt heater will take 0.3823hrs? My empirical evidence doesn't support this result.
Even at 20% transfer I get 1.91hrs, still nowhere near the empirical result.
Or is my 1000watt melting pot just really that bad at transfering the heat to the metal?
thanks
Nick
I love materials science!
If I know my mass, Cp, Mp and Ambient I can calculate the number joules required to make the mass of metal reach the Mp. How do I figure time?
Joules are convertable to watthour, I know the wattage of the heater, so then do I just divide the two?
IE: 20Kg, 0.167 J/gm*C, 138C, ambient 20C
Res: 394120J
Converting gives: 109.5 watthour
The heat required to get over the heat of fusion (Hf) is given by:
mass*Hf = 982000J
and conversion gives: 272.78 watthour
So the total required heat to melt 20kg of metal is 382.28 W*hrs
Do I just divide by the wattage? (I know that this is assuming 100% effective transfer of heat, but some assumption is always necessary.)
So a 1000watt heater will take 0.3823hrs? My empirical evidence doesn't support this result.
Even at 20% transfer I get 1.91hrs, still nowhere near the empirical result.
Or is my 1000watt melting pot just really that bad at transfering the heat to the metal?
thanks
Nick
I love materials science!