Power is totally relevant to vapor production. It is in fact as relevant if not more relevant than surface area in out case.
Watts is power. Power is Energy per second. A Watt is a Joule/Second (Joule is a measure of energy).
Heat is energy(thermal energy). It can be measured in joules.
Heat Transfer rate is the rate at which thermal energy is flowing. This is power. You're going to get a little bit confused here.
Heat transfer is commonly measured in terms of Heat Flux. Heat flux is Watts/m^2. That's watts per meter squared. Thats power per area. It describes the rate of heat transfer with respect to the contact area of two objects.
Simply put, If you take a hot object and place it in contact with a cold object, the heat transfer is greater the larger the contact area. Heat Flux accounts for that. I'll get back to this.
Temperature is a measurement of the average kinetic energy of the particles in a substance (I had to look this one up because the definition is tricky).
Thermal Energy is the kinetic energy from the motion of particles in a substance.
So the movement of the particles(atoms and molecules, etc) in heat. It determines how much energy it has.
Temperature is an average measure of that. Its kind of like voltage. A 10440 and a 18650 are both 4.2V but we know the 18650 has a lot more energy stored.
Similarly a piece of steel and a piece of wood can have the same temperature, but the steel is going to hold more thermal energy.
Boiling point is the temperature at which the vapor pressure of a liquid exceeds the surrounding pressure exerted on it. Simply the molecules are able to jump out and escape into a gas.
Boiling point goes down with decrease in pressure (This is important to us)
Heat of Vaporization is the amount of energy required to transform a given amount of a substance from a liquid to a gas. For PG it is 67 kJ/mol. or 880 Joules per gram or 880 Joules per ml. (Some rounding involved do the math your self if you want great accuracy. Heat of vaporization can also vary due to temperature and pressure.)
Nichrome wire converts electricity to heat with very high efficiency.
The coil is often submerged in the liquid
That heat is then transferred from the coil to the liquid. Much like boiling water, when the liquid reaches a certain temperature and continues to be heated, it vaporizes. That vaporization process takes with it energy (heat).
Heating 0.1ml of PG to its boiling point will take approximately 37 Joules of heat. If you want that to happen the first second you push the button, that 37 watts. But other things are happening that don't make this exactly true.
Let's say you use 0.1ml of liquid in 10 seconds. That would take 8.8 watts of power for simply vaporizing the liquid. This doesn't include heating the liquid to its boiling point. But other things are happening that don't make this exactly true.
When you suck on an e-cig you create a localized vacuum. This reduces the boiling point and causes more of it to vaporize. This reduces the time/heat required to raise its temperature, and reduces the heat of vaporization.
If you noticed, you atty/e-cig/finger/etc get hot. Thats because heat is escaping to the outside. The larger your coil the more likely this is to happen. The liquid as it is heated transfers heat to the outside of the atty. So we have some escaping power there.
The liquid is also warmer on subsequent hits. If you noticed, vapor production is higher since the liquid is already warm and requires less heat to reach its boiling point.
Thats probably a lot more info than you needed. I need to get back to why power matters more than temperature.
Saying temperature is more important than power is akin to saying a 4.2V battery is the same as any other 4.2V battery. We all know a 14250 battery isn't going to hold a candle to an 18650. Or comparing a fire hydrant to a super soaker as long as the pressure is the same.
Lets say we took two identical pots of water. Stick one in the oven and set it to 212 Fahrenheit set the other on the stove and turn it on med-high. Wait 30 minutes and see which one has boiled off more water.
Every molecule of vapor produced will take with it a certain amount of heat. That heat needs to be constantly replaced.
Now with that being said, I will try to answer the question of what the boiling point of
juice is.
The boiling point of every liquid is going to be different based on its composition. Propylene Glycol is 188.2 °C (370.8 °F) and Glycerin is 290 °C (554°F). That's assuming pure composition. Most mixture include some water which will reduce the boiling points. Flavors and additives will also effect the boiling point just like adding
salt to water makes it boil at a higher temperature.
Boiling points vary with air pressure as well. This is why you see little vapor until you start sucking on it.
Now the max temperature of a dry, bare coil is going to be different than that coil when it is wet and producing vapor.
