@jmowbray I am trying to picture your chiller. You said it comes in at the bottom and points up to the top. Does the pipe go all the way to the top so that the fog comes out at the top and spills over and then down through the ice? Or does the tube face up but stop near the bottom, pushing the fog through the ice (from the bottom going up to the top), and if that is the case, where is the outlet? Maybe add a picture if you can?
The thing is.. you want an expansion area for the fog that just came out of the fogger to expand. By having that area, it gives the fog more density before it comes in contact with the ice. If you push it through the ice right away, before it has had time to expand with air, you'll lose some of that to.. I forget the right word.. basically some of the fog turns back in to the fog fluid, and thus you are losing fog volume and potentially density as well without the area to expand.
It doesnt mean you are doing it wrong. Just having followed the designs since the late 90s until now, it seems the most effective route, is for fog to have the ability to expand a bit before it comes in contact with the ice so that its denser.
The other thing that is good which I didnt do with my chillers but may do one day.. is consider that the more room the fog has that its not contacting ice inside, the more likely it will lose some of its density.. er.. or something like that. In other words, you want the fog to expand, hit ice and billow out of the outlet.. not float around above the ice. for a bit before it finds it's way out. I built the design where it comes in at the bottom, has expansion area.. ice sits on a rack above the expansion area.. the fog, being hot.. rises up through the ice, and then the outlet is facing up towards the top, and L loops back out the other side, so the fog that rose up through the ice now goes out the L tube that has an opening near the top. The problem with this design I think is that there is an expansive area above the ice (to the top of the lid) that may cause me to lose some fog potential as well. However, this seems to be the same or similar design that some of the commercial fog chillers for like $120 or so follow, so maybe I am misunderstanding the chilled fog flow.. does it all migrate to the opening at the top efficiently, or does some of it linger around for a bit, warming up and just interfering with the flow of the fog? That I am not entirely sure of.
I think honestly the best fog chiller I had was a long corrugated tube of 3" size (broke the 4" rule though) and drilled little holes along the way. I packed it with ice and dry ice, and the fog came out perfect. No cooler, etc.. just fog blowing in to this long 12 foot length full of ice/dry ice. There are problem with it too though. The ice melted pretty fast and had water in the tube for some time, which I am sure affected the fog output after a while. Not only was it not as cold, it was taking up room.. and I also wonder if the corrugated material affect fog flow. Plus, if any wind kicked up, it was impossible to reposition because it was so long and had output all over the place. Anyway.. initially it worked great, and I only needed it for a couple hours anyway.. most kids come between 6 and 8pm on school nights anyway.
Amazing the time, money and work we put in to a couple hours of kids coming around.