Heat Coil Calculation

Status
Not open for further replies.
N

nuckythompson

Member
Location
Nova Scotia
Occupation
Electrical
Hi there, I am wondering about building a small coil space heater. I want the coil to give off about 100W of heat. Does anyone know what equations I could use to figure this out? I am guessing it would include weight/length/gauge, specific heat of the coil material, delta T, and time. The coil would be open air, not trying to heat any liquids.

Appreciate any help :)
 
nuckythompson said:
Hi there, I am wondering about building a small coil space heater. I want the coil to give off about 100W of heat. Does anyone know what equations I could use to figure this out? I am guessing it would include weight/length/gauge, specific heat of the coil material, delta T, and time. The coil would be open air, not trying to heat any liquids.

Appreciate any help :)
Click to expand...
Wait.. would I just use P=IV and P=I^2*R? If i wanted to make a 100W heater with a 9V battery, the coil would need resistance of 0.81Ω? But then how do i change heat up time?
 
Okay I think I have it, let me know if I am wrong.

I would use the following to solve for wattage required to get the temperature and temperature change time I want.

kW = (WT x Cp x Δ T)/3412 x h
Where:
kW = your kilowatt requirement
WT= the weight of the material to be heated, in lbs.
Cp = the specific heat of the material to be heated, in BTU/lb°F
Δ T = Temperature Rise, in °F
3412 = Conversion Factor, BTU/kWh
h = how long it should take to reach the temperature set point, in hours

Then I would use ohms law and the resistivity of the coil material to find the resistance required to get that wattage.

I know I could just buy a 100W resistor, but I am more curious on how it is designed and how I could maybe make one with a small battery.
 
nuckythompson said:
Okay I think I have it, let me know if I am wrong.

I would use the following to solve for wattage required to get the temperature and temperature change time I want.

kW = (WT x Cp x Δ T)/3412 x h
Where:
kW = your kilowatt requirement
WT= the weight of the material to be heated, in lbs.
Cp = the specific heat of the material to be heated, in BTU/lb°F
Δ T = Temperature Rise, in °F
3412 = Conversion Factor, BTU/kWh
h = how long it should take to reach the temperature set point, in hours

Then I would use ohms law and the resistivity of the coil material to find the resistance required to get that wattage.

I know I could just buy a 100W resistor, but I am more curious on how it is designed and how I could maybe make one with a small battery.
Click to expand...
I though this project was about heating air? Presumably, a steady stream of air flowing through the heater?

Don't neglect the internal resistance of a battery, or its energy content.
 
Status
Not open for further replies.
Top