Selecting Kanthal Wire Diameter for 120W 12V Heaters at 25cm Length

Please help me solve this problem.
I want to build several 12V heaters with different wattages and lengths.
The problem is that I don't know what diameter of the resistance wire to choose. If I choose a wire that is too thin and short, it will glow quickly and burn out. Can I use a thicker one, but how thick? Does too much thickness have any negative effects?

How to determine the power that a wire can give off to the environment, without skoda for itself? What formulas to use?
Maybe the easiest way is to experimentally test the different variants?

Let's assume that I need to build a 120W heater with a voltage of 12V. Ideally, the wire should be 25 cm long.

Is this proposition good ?:
25 cm of Kanthal wire with a diameter of 0.6 mm and a resistance of 4.8 Ohm / m. Then the resistance of the wire would be 1.2 Ohm. I = 12V / 1.2R = 10A, P = 12V * 10A = 120W

Hello.
Look:
http://www.artom.com.pl/Promienniki/0013.htm " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > http://www.artom.com.pl/Promienniki/0013.htm
Greetings.

Your calculations are correct. Just to find a power supply that will pull from 12V - 10A. (maybe a car battery?)

The calculations seem to be correct, but now it seems to me that they are not correct. After calculations in the calculator provided by Ryszard49, it turns out that the surface load is an important factor. For my case and a 0.6mm wire, it would be of the order of 26W / cm2. It is stated under the calculator that for 1300 degrees the load should be 0.8 - 1.0 W / cm2, and already at 900 degrees C it should be 3-3.5 W / cm2. But how do I know to what temperature my wire will heat up? Rather, I have to see it experimentally and assess it by eye, because calculating it will probably be complicated. Moreover, it is not known what the permissible load would be if, for example, the wire obtained only 500 degrees Celsius
In the Kanthenal catalog, depending on the method of application, it can be seen that the load varies from 1 W / cm2 to even 60 W / cm2.

In my case, based on the calculator, it appears that I should use a wire with a diameter of 1.3 mm and a length of 1.14 m, resistance 1.05 Ohm / m. Then the surface load would be 2.5 W / cm2. It is, however, a bit large in diameter and length, and I don't like that.

For now, I use a computer power supply, so there is no problem with the amps.

I know the topic is old but a lot of people find their way here via google (like me).
In my case, I needed to select a temperature of 600 * C for cutting styrodur (XPS).

A very good calculator in the attachment:



You can smoothly calculate what we need on the sliders.
When you need a given temperature, you can set it and choose the rest of the parameters.
Once you have the power supply, you can set the voltage permanently and choose the rest.
I recommend!

Unfortunately, flash is required to run