Does Wire Gauge Affect Surface Heating Efficiency in Resistance Heating?

[madskier8806]

hi all

I am trying to use a circuit of NiCr wire to heat a surface. I have setup my circuit using parallel 'branches' of NiCr connected to a bus so that voltage is equal across each branch. I am an undergrad EE so I get electrical aspect, but have little knowledge of the thermo.

My problem is spreading out the heat.

My first question is will a larger gauge wire provide better heating over a larger surface?
NiCr wire spec can be found here: http://www.heatersplus.com/nichrome.htm"

I have experiemented with 2 gauges: 22 and 18 gauge and I found that the 18 gauge wire provided more heat over a surface than the 22 gauge wire at equal current levels. Does this make sense?

Second question:

I need to cover a large area, have a large number of branches, and have a high enough branch resistance so that the total resistance of my parallel circuit will not be too low. The circuit is setup so that the branches go straight across the surface from bus to bus, like the lines on a sheet of notebook paper.

The area is 8 feet wide. With the 22g wire I used 8 foot long branches from bus to bus, with the 18g wire I need to use 16 foot branches (doubling back, both buses on one side of circuit). The total power in the 22g branch is ~24W (1.724A) and the total power in the 18g branch is ~30W(2.154). Will the fact that the 18g branch is twice the length of the 22g branch reduce its surface heating effieciency?

My thinking is that it should not, because every delta x length along the wire should be disapating ~30W

Thanks for the help!

 

[mgb_phys]

The limiting step is likely to be coupling the heat from the wire into the surface, thermal conduct across joins is always difficult.
A thin wire might be better able to follow the surface profile.

 

[astrokreng]

I can provide some insights and suggestions based on your questions and experiments with the NiCr wire circuit.

Firstly, the gauge of the wire does play a role in the heating efficiency. Generally, a thicker wire will have a lower resistance and therefore can carry more current, resulting in higher heat output. However, in your case, the 18 gauge wire seems to be providing more heat than the 22 gauge wire at equal current levels. This could be due to the fact that the 18 gauge wire has a slightly higher resistance per unit length compared to the 22 gauge wire, resulting in more heat dissipation along its length.

Secondly, the length of the wire does not necessarily affect its surface heating efficiency. As you mentioned, every delta x length along the wire should be dissipating the same amount of power. However, it is important to consider the total resistance of the circuit when using longer wire lengths. If the total resistance of the circuit becomes too low, it could result in a higher current and potentially damage the circuit. So, it is important to carefully design and calculate the appropriate length and gauge of wire for your specific circuit to ensure safe and efficient heating.

In terms of spreading out the heat over a larger surface, you could consider using multiple parallel circuits with shorter wire lengths to cover the 8 feet wide surface. This would allow for more even heat distribution and reduce the risk of overloading the circuit. Additionally, you could also consider using a different heating element or adjusting the voltage and current levels to achieve your desired heating distribution.

Overall, it is important to consider the electrical and thermal properties of the materials and circuit design when using resistance heating for surface heating applications. I hope this helps and good luck with your project!