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loclboy

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I have a product idea. It needs to generate enough heat to melt 1/2" of ice off of an area approximately 18sqft in ambient temperatures down to -10 F; be battery powered(12V rechargeable); flexible yet durable. I am electrical knowledge challenged, and have no idea where to start. I have seen various heating elements, ie. Kapton, carbon fiber, etc., but have no idea how to determine heat/resistance calcs on various heating elements, or which type of battery will have the capacity to generate enough heat to do the job! Can anybody point this sorry "marketing" type in the right direction?
 

BrownOut

Banned
You need to start with the thermal properties of ice. What you're talking about is a phase change, so there is alot of latent heat energy involved. The math is simple for your problem, so start looking up the equations, then after you've calculated the energy requried, then you can determine if there is enough energy in your battery to accomplish what you want.
 

loclboy

New Member
Yes, Nigel. Your comment poses an interesting question. How does an automobile rear defroster develop enough power to do the job?
 

BrownOut

Banned
If your defroster can melt 1/2" of ice in -10F, then that's one hell of a defroster!
 

mneary

New Member
At -10F, my defroster takes 10 minutes to dispose of a microscopic coat of ice, and there's no evidence of melting. I think it sublimates in that environment.

18 square feet, half an inch thick is 1296 cubic inches. (It's also more than 5184 square inches exposed.) I'm going to use metric because imperial measure is so confusing to me. 1296 cubic inches of ice is about 21kg. To raise this mass 75 degrees C (42 degrees F, -10F to 32F) would require 33 kiloJoules and it's not begun to melt. If your 12V battery can provide 10A, that's 120 joules per second. Your ice is raised to 32F in 3-1/2 hours.

It hasn't even begun to melt, though. You need another 16-1/2 hours to melt it.

If your 36 square feet (18 on top, 18 on bottom) is exposed to an outside environment of any kind, your heater will have no measurable impact.
 
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kchriste

New Member
Forum Supporter
Is this 1/2" of ice on a sloped surface? If so, you won't need as much energy to melt it enough to make it slide off and crash to the ground. If you need to melt the entire thing into water, then that is another matter. ie: How would you stop the runoff from refreezing somewhere else?
 

Mr RB

Well-Known Member
If you keep the area heated JUST above freezing then ice won't form on it to start with. That has to be more energy efficient than trying to remove ice later.
 

MikeMl

Well-Known Member
Most Helpful Member
I have a product idea. It needs to generate enough heat to melt 1/2" of ice off of an area approximately 18sqft in ambient temperatures down to -10 F; be battery powered(12V rechargeable); flexible yet durable. I am electrical knowledge challenged, and have no idea where to start. I have seen various heating elements, ie. Kapton, carbon fiber, etc., but have no idea how to determine heat/resistance calcs on various heating elements, or which type of battery will have the capacity to generate enough heat to do the job! Can anybody point this sorry "marketing" type in the right direction?

Either figure out Thermodynamics, or hire an engineer that already understands it. You ain't gonna like what he/she tells you, though. Please don't shoot the messenger.
 
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