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Coils: Do thicker wires ACTUALLY give you a warmer vape?

Published by TheKiwi in the blog TheKiwi's blog. Views: 7691

This blog was conceived more as a rant than an actual informative post. But I guess nobody likes a whiney crybaby, so I'll go ahead and try my best to explain some stuff that's been bugging me.

SO. what IS this blog post about? I've been around the forums and noticed a very common misinformation floating around: If you want a warmer vape, use lower gauge wires. Before anyone starts throwing a fit and start quoting RipTrippers, calm down and let me explain this in a purely scientific way.

To do so, let me first start off by getting certain scientific concepts and definition out of the way:

Concepts and Definition:

1) Ohms law: if you don't understand this, please go ahead and look up on google to understand the classic V = RI equation, and how that relates to power/watts: P = IV = (I^2)R = (V^2)/R.

2) Relationship between Power (watts) and heat energy (Joules): Here in the vaping world, there is often liberal use of both power and energy to describe the heat that we get from the coil. There really isn't a big deal in doing so for our applications, but for those curious,

Joules = Watts * Time (in seconds)

ex. if you pumped 30 watts of power to a coil for 2 seconds, the total heat energy to the coil is 60 Joules.

3) Specific Heat Capacity: To make this as simple as possible, the specific heat capacity refers to how much heat energy is required to raise the temperature of a unit volume of material by 1 degrees.

As such logically, the units associated with specific heat capacity is: Joules (heat energy) per mass (g) per temperature degree.

Ex: if an object with a mass of 1g has a specific heat capacity of 215 joules/g/K, then supplying the object with 430 Joules will raise its temperate by 2 K.

NOW, because specific heat capacity refers to the heat capacity for a UNIT VOLUME, this means that regardless of what object you're talking about, as long as they are made of the same material, they ALL have the same specific heat capacity. i.e. a oceanliner made of kanthal has the same specific heat capacity as your wires. yes.

4) Heat capacity: Unlike the specific heat capacity, the Heat capacity accounts for an entire object, rather than for a unit volume of an object. Here's an example:

Lets assume that 1 inch of XX gauge kanthal has a mass of 1g. Lets assume that the specific heat capacity is 213 J/g/K

So, if you wrap a coil using 3 inches of the same kanthal, then the heat capacity of the ENTIRE coil is
3 * 213 = 639 J/K, meaning you will need 639 Joules in order to raise the temperature of the wire by 1 K.

5) Relating gauge of wires to mass and resistance: Now. The way the kanthal wire gauge size relates to resistance is as follows: Every 3 gauge size you drop, the resistance and mass is approximately halved.

For example: comparing 33 ga and 30ga wires:

Resistance of 33ga = 16.6 ohms/ft
Resistance of 30ga = 8.36 ohms/ft

Length per pound
33ga = 8217 ft
30ga = 4142 ft


SO. Now that we have all these out of the way, What does it mean?

For the sake of a meaningful inquiry, we will vary one parameter, and keep all others constant. In the case of our application, it simply means that we will keep wattage and resistance constant, and vary only the gauge of wires.

Using the 33ga and 30ga examples above, consider the following:

Because the resistance of 30ga is HALF that of a 33ga for the same length, we will need 2x the length of 30ga wires in order to achieve the resistance of a specific 33ga build.

Because the mass per length of the 30ga is TWICE that of the 33ga for the same length, then in total, for 2 builds of the SAME resistance, the mass of a 30ga build will be 2 x 2 = 4 TIMES that of the 33ga build.

Now, here's the kicker: as mentioned previously, ALL kanthal wires will have the same SPECIFIC HEAT CAPACITY.

BUT! because heat capacity is linearly correlated to total mass, it then follows that the HEAT CAPACITY of the 30ga build is also 4 TIMES that of the 33ga build.

Which then means that if we pump 30 watts (lets assume a firing time of 1 sec. this means that 30 watts will give us 30 joules of heat energy) into both builds,

the 33 gauge build will gain 4 TIME as much temperature units as the thicker 30gauge wires.

SO. point being: using thicker gauge wires WILL NOT give you a warmer vape. On the contrary, it will give you a much cooler vape.

Now, there IS a caveat to this:

there is ONE scenario when using lower gauge wires will give you a warmer vape, and then is ONLY when you drop the resistance AND keep the voltage constant (eg when using a mech): i.e. you use less wraps, and go for a lower resistance.

This happens because by decreasing the number of wraps, you lower the heat capacity of the whole coil. (keeping the same number of wraps will simply reduce the increase in heat capacity compared to a higher gauge wire). At the same time, the lower resistance will pull a higher current, resulting in higher wattage and thus heat energy, giving you a warmer vape.

In conclusion, using thicker gauge wires DO NOT naturally lead to a warmer vape. On the contrary, there are far more cases when using a thicker gauge wires will lead to a cooler vape. THE ONLY way that thicker gauge wires can give you a warmer vape, is if you overcome the increase in heat capacity of the coil by exponentially increasing the wattage supplied to the build (e.g. lowering the resistance of the build to draw more current).

So there we go. I hope that we can have less people throwing out "oh just use a thicker wire" as a solution every time someone asks for a warmer vape. It just isn't universally true.
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