# Need help calculating the heat of a wire wrapped

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1. Feb 27, 2015

### devinA

Okay so before I get torn to shreds let me say I am coming to the gurus for knowledge because I am severely lacking in it.

So here is what I am trying to do. I am trying to figure out how to control the temperature of a wire when coiled or wrapped around a small glass tube. I am using 32 gauge kenthal wire I believe the resistance is 13.75 ohms per foot. Let's say I am using a foot of it to keep it easy. I guess my question is: is there a way to calculate the amount of Power (watts?) it is going to take to heat the wire to a specific temperature range? Say between 320-430 degrees F?

Things I know I don't know:
Will the diameter of the thing it is wrapped around change the outcome? or is it just based on the length and resistance of the wire? ( I read some formulas about the cross sectional area is that the space in which it is wrapped length wise along the thing I am wrapping?) just wasn't exactly sure on this

Would there be a way to limit the voltage or wattage to get the wires to reach a certain temperature and stay at that temp? (for the most part I know there will be heat loss and stuff like that)

I am trying to do this as "mechanical" as possible I guess I mean to say I want to use the most simple things I can to accomplish desired effect even at the cost of some efficiency or complete accuracy.

Any and all tips and criticism is welcome, I know I do not know what I need to and I am humbly asking for help.

2. Feb 27, 2015

### Quantum Defect

We used to use a set-up like this (with nichrome wire) to do pyrolysis reactions in a quartz tube under vacuum. You are likely going to lose a lot of heat unless you insulate the system. We would use glass wool to insulate our set-up. My guess is that insulation of the system is going to be the thing that limits the temperature that you will be able to achieve.

Recognize that a constant temperature means that the heat in (I^2R heating) equals the heat out. The heat out is going to depend upon the rates of heat out for the various loss mechanisms. Insulation minimizes some of these loss mechanisms.

3. Feb 27, 2015

### devinA

So instead of trying to calculate everything out would this be a better situation to approach by testing and measuring? I was planning to insulate with high temperature grade silicone

4. Feb 27, 2015

### Quantum Defect

I would try first with something you could remove, like a fiberglass sleeve, etc.