I decided to start a new thread as a spinoff of some great discussions from a few other threads. This is an initial experiment that ill add to as I have more time to play around with it and get some equipment and materials better than what I happened to have on hand. The hypothesis is any atomizer build that actually works will reach a certain maximum temperature (at the phase change of the juice from liquid to vapor) and won't get any hotter, no matter how much energy we continue to add, until the wick dries out.
My initial results seem to prove the hypothesis. Here we go...
First two photos are the test setup with a thermocouple embedded in a standard silica wick and coil assembly. The thermocouple is just a piece of kanthal twisted to a piece of nichrome. No cold junction compensation and no calibration. At this point, I just want to see the time/temp curve -- the actual exact temperatures aren't important at this point. The scope is set to 1mV per vertical division and 5 seconds per horizontal division. The coil is powered by a power supply delivering about 16 watts, also not super important as long as its enough power to overdrive the wick as it dries. The rest of the crap on the bench is a bunch of filtering to prevent the power supply noise from coupling into the 1mV vertical amp (juice is conductive at these sensitive levels, as I found out the hard way, so I had to get rid of the noise from the supply or the thermocouple output turns into hash).
The third photo (bottom left) shows the trace of a dry wick. The thermocouple output plateaus at about 4 divisions above room temp and I turned the supply off at mid-sweep, about 25 seconds as that is as hot as 16 watts would get it. The last photo (bottom right) shows a wick saturated with PG. It plateaus at less than one vertical division up through just shy of 30 seconds, at which point it gets dry and the temp shoots upward.
The only difference in any functioning atomizer build is all in the rise time of the trace in the first few seconds (how fast it gets to the phase change temp). Future experiments will start to look at the differences there.
This was a lot of fun to do.
My initial results seem to prove the hypothesis. Here we go...
First two photos are the test setup with a thermocouple embedded in a standard silica wick and coil assembly. The thermocouple is just a piece of kanthal twisted to a piece of nichrome. No cold junction compensation and no calibration. At this point, I just want to see the time/temp curve -- the actual exact temperatures aren't important at this point. The scope is set to 1mV per vertical division and 5 seconds per horizontal division. The coil is powered by a power supply delivering about 16 watts, also not super important as long as its enough power to overdrive the wick as it dries. The rest of the crap on the bench is a bunch of filtering to prevent the power supply noise from coupling into the 1mV vertical amp (juice is conductive at these sensitive levels, as I found out the hard way, so I had to get rid of the noise from the supply or the thermocouple output turns into hash).
The third photo (bottom left) shows the trace of a dry wick. The thermocouple output plateaus at about 4 divisions above room temp and I turned the supply off at mid-sweep, about 25 seconds as that is as hot as 16 watts would get it. The last photo (bottom right) shows a wick saturated with PG. It plateaus at less than one vertical division up through just shy of 30 seconds, at which point it gets dry and the temp shoots upward.
The only difference in any functioning atomizer build is all in the rise time of the trace in the first few seconds (how fast it gets to the phase change temp). Future experiments will start to look at the differences there.
This was a lot of fun to do.
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