Here’s my new fog chiller.
Pretty radical huh?
You know what they say, ‘it’s what’s inside that counts.’
My old fog chiller works ok. It got a lot better when I started using a 10-foot ABS tube as a secondary chiller and fog dispersing manifold. (Got that idea here. Thanks everyone.)Pretty radical huh?
You know what they say, ‘it’s what’s inside that counts.’
I have seen several fog chiller designs on this forum and it got me thinking (and my family nervous). My goals were to maximize the cold surface contact area while minimizing the system pressure drop due to resistance to air flow.
The concept I came up with is a three-level cooling chamber. The fog would enter Level 3 and spread out over the top ice layer. The fog would flow through gaps in the ice to Level 2. Flowing through gaps in middle ice layer the fog would finally end up at Level 1, over another layer of ice as it flowed towards the output and the 10-foot manifold pipe of filled with bottles of frozen water.
Note: The holes I drilled in the ABS tube get progressively larger as the distance increases from the fog chiller. I get a fairly even flow along the whole length. Hurray for fluid dynamics.
_
The middle level needs a support to lift the cooling layer just above the fog chiller’s output pipe. Using the old standby, pvc pipe, I made a frame with legs and one end open to accommodate the output pipe.
1. Place the middle-level support in the bottom of the tub.
Note: The tub is a Roughneck by Rubbermaid.
2. Pack ice in the bottom as tightly as you can but leave space between the top of the ice and the bottom of the middle shelf.
_
I fabricated the support shelf using ¼” hardware cloth sandwiched between two layers of really thin plywood. I treated the plywood with copper naphthenate to protect it from moisture damage. Stainless steel bolts and cap (acorn) nuts hold the assembly together.
Safety Note: Do not treat the wood until all of the cutting, sanding and drilling is finished. Use protective gloves when handling copper naphthenate. It is safe when dry, but dust from machining treated wood is more toxic than plain plywood dust (which is already toxic enough). A respirator is not a bad idea.
Note There is always one orientation of the shelf the fits easier in the tub. I marked the shelf so I place it the same side up and same direction every time.
3. Put the middle level shelf in the tub.
Note: This is where you will be glad you didn’t try to make it air tight. But it should be close. We want the fog to go through the ice layer, not around it.
4. Put ice on the shelf so it is fully covered and shallow enough to leave a gap between the top of the ice and the bottom of the top shelf.
Note: The ice should also be loose enough to let the fog pass through the ice layer.
_
The top shelf will sit on a ridge the runs most of the way around the tub about 1/3 of the way down from the top (highlighted in this photo).
The construction method is essentially the same as the middle level shelf. The complication is the gap needed for the chiller’s input pipe.
I installed window seal foam on the lid to limit fog escaping from the chiller.
Note: I have noticed people complaining if any fog escapes anywhere but the output nozzle. Personally, I want some un-chilled fog to escape. I like mist in the air. You will see in the final photo that really cold fog laying on the ground can look odd. I’ve seen ground fog; there is never a sharp line between clear air and fog. You see that against the camouflage fog dam in the last photo.
5. Place the top level shelf in the tub.
6. Arrange a layer of ice to cover the entire shelf.
Note: The ice level will be lower down the middle of the shelf so the fog can spread out better.
I originally made an input diffusion manifold the went the length of the shelf. It had holes on either side to blow fog to the sides. However, I decided to try something different first.
Normally I would use several bags of ice. My old fog chiller used 40 pounds of ice. This works, but it takes several days before the ice melts enough to remove it from my old chiller. I decided to take a chance and use cold packs. I knew I could fall back on my old chiller if this didn’t work.
* * * But it worked great. * * *
If you don’t have enough cold packs you could add ice to make up the difference. I was concerned about not using ice because of some comments I’d read about needing the melting water to add weight to the fog. That was not a problem. And it was hardly dry in the chiller. Moisture in the air was already condensing on the cold backs as I loaded them into the fog chiller.
7. Put in whatever you’re using to chill the fog so that it covers the top shelf.
Tip: Leave gaps in the cold pack stacks so fog can pass through to the next lower level.
8. Put on the lid.
9. Connect the fog machine to the chiller input.
10. Connect the 10-foot ABS manifold to the chiller output.
11. Fill the manifold with bottles of frozen water and cap the end.
Note: I use a soft endcap and band-clamp for ease of installation and removal.
12. I cover the fog machine with a tent made of camouflage tarp that hangs about half way down the pvc frame.
Note: This both protects the fog machine and hides it.
13. Turn it on. (I had to add this to get thirteen steps.)
_
The graveyard is surrounded by a fog dam. I got cheap camouflage tarps from harbor freight and cut them in half lengthwise. I strung paracord between the fence and porch to support the tarps across the yard. Tarps also line the bottom of the fence. Next to the walkway I use clear plastic panels held in place with 12-inch galvanized spikes. Better placement of props would totally hide the spikes. I highlighted the clear plastic panels in this photo, but in the last photo you will see they are practically invisible. This keeps my chilled fog where I want it, mostly. High winds will cause problems, but gentle breezes leave things pretty much alone.
To the left is the walkway lined with luminaria. You can see the walkway is clear while a good layer of fog is pooling behind the clear plastic dam. Toward the back of the graveyard you see the oddly sharp line between the fog and the clear air. It was a really calm night with no wind. I think changing up some of my lighting might help.
Well, that’s my first contribution to this forum. I hope you liked it.
Thevuse of a fog dam is an inspired idea - prevents fog from obscuring the walkway, which can otherwise lead to falls.
