- #1
eng3
- 7
- 0
I am trying to estimate the amount of electrical power needed to heat up a material from 20C to 1000C in 20 seconds. Assuming it is 18sqin and 3mm thick, I used the specific heat which was given as 0.78 J/gC and weight 11.39g (from the destiny of 3.26).
0.78 J/gC x 11.39g x (1000C - 20C) / 20sec = 435 J/s = 435 W.
Now I know I've left out some heat losses.
I estimate Radiation at 1000C with an emissivity of 0.85 would be around 1470W
Convective loss around 377W with a 25mph wind
If heatup is linear, I would expect maybe half of that would be the losses during warmup are around 950W
so perhaps a total of 1400W needed for the heatup
Reading data from the manufacturer, they tell me that 700W/sqin (12600W total) are required to heat it from 20C to 1000C in 20sec. I asked them why so much and they say it has a "Temperature Coefficient of Resistance" of 0.0015. I showed them my calculation, they tell me that will give an average power needed, but 12600W is required at the start.
That makes no sense to me as I would expect the power to be constant and I am unfamiliar with this TCR coefficient. How is TCR related to Specific Heat?
What am I missing?
0.78 J/gC x 11.39g x (1000C - 20C) / 20sec = 435 J/s = 435 W.
Now I know I've left out some heat losses.
I estimate Radiation at 1000C with an emissivity of 0.85 would be around 1470W
Convective loss around 377W with a 25mph wind
If heatup is linear, I would expect maybe half of that would be the losses during warmup are around 950W
so perhaps a total of 1400W needed for the heatup
Reading data from the manufacturer, they tell me that 700W/sqin (12600W total) are required to heat it from 20C to 1000C in 20sec. I asked them why so much and they say it has a "Temperature Coefficient of Resistance" of 0.0015. I showed them my calculation, they tell me that will give an average power needed, but 12600W is required at the start.
That makes no sense to me as I would expect the power to be constant and I am unfamiliar with this TCR coefficient. How is TCR related to Specific Heat?
What am I missing?