# Using Velocity in your Chiller Build!



## Skiddy (Oct 8, 2012)

So I just finished building my new chiller for this Halloween. As I was designing it, I was reminded of the plumbing for my homebuilt computer cooler. I figured I would do a few tests to see if I could use some math to refine my design. Here is what I ended up with:

I have 24 ft of 2.25" tubing running in a helix from the fogger to the outlet. The outlet is a smooth transition from 2.25" to 3". Below is a list of the items I used (all from the local Lowes).

1 2.25" 90 degree PVC elbow
24 ft of sump pump discharge hose 2.25 diameter
1 2.25 to 3" PVC adapter
1 27 qt storage bin

Now for the calculations:

The test fogger I used produces 2000 ft3/min of fog as per the sticker. Enter this into an air pressure drop calculation (turbulent flow) and the total pressure drop along the length of 2.25" tubing is 29.5699 psi. After traveling through the 24' of tubing the the fog hits the 3" adapter and the pressure drops an additional 15.9575 psi. This equates to slightly over a 45.5 psi pressure drop that results in a velocity of approximately 28 ft/sec at normal atmosphere.

Great, so I know how to use a calculator - what does this mean?
In addition to using a temperature difference to keep the fog low to the ground (hot air rises, cold air falls - colder air is more dense, etc.) the effects of velocity on the fog can cause it to spread out too fast and dissipate or to appear very thin. This same principle works on your garden hose as well - put your finger over the end and the water sprays farther.

Once again, so what?
Causing your fog to slow down (lose velocity) as it approaches and passes through the output of your chiller will provide a much denser, longer lasting fog. I have included a video of the chiller I built without any ice in it. This is just the tubing and adapters. I used a cheap Walmart 400 watt fogger and Froggy's Freezin Fog Juice.


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## Skiddy (Oct 8, 2012)

Err - the final velocity unit should be ft/min not ft/sec. That would be some fast fog!


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## Machiavellian (Sep 2, 2013)

Very interesting concept I always knew there was more science involved than just cooling the fog. I would like to see some pics. or a vid with ice, and see what type of difference it makes after the modifications you made.


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