Aquafog fogger.

[DavidCampen]

I plan to install an Aquafog 700 in my new 10ftX20ft greenhouse in Southern California. I hope that it will be adequate for my humidification and summer cooling needs. The Aquafog will be connected to a humidity controller and fed RO water. In conjunction with the Aquafog I will have a 2000 CFM exhaust fan connected to a high temperature controller.

Is anyone else using Aquafog foggers?

[raybark]

I have one and I love it.

I use RO water in it, with the overflow (there is some coalescing of drops inside the housing that need to drain) running back into the RO tank.

You can certainly count on the unit to maintain your humidity, but it won't have as much cooling effect as you're probably hoping for due to the fact that you'll be working with a relatively small volume of air at elevated RH.

[DavidCampen]

I posted a long reply here yesterday but it disappeared into the void waiting for moderator approval. This is a test to see if I am able to post today. If so then I will take the half an hour necessary to recreate my post from yesterday.

[DavidCampen]

Originally Posted by raybark

I have one and I love it.
...
You can certainly count on the unit to maintain your humidity, but it won't have as much cooling effect as you're probably hoping for due to the fact that you'll be working with a relatively small volume of air at elevated RH.

That is where the 2000 cfm exhaust fan comes into play.
According to this psychrometric chart:

http://www.sp.uconn.edu/~mdarre/NE-1...ric_inset.html

2000 CFM of air at 90 degF and 40%RH will require about 30 pounds/hour of water to increase the humidity to 80% while decreasing the temperature to about 76 degF.

This cooling calculation does not of course take account of solar heating but I am hopeful that with the 2000 cfm fan and 25 pounds per hour of evaporated water I should be able to hold the interior temperature to at least no higher than the exterior temperature.

[raybark]

I have studies psychrometry extensively, and understand it quite well, so your calculation is probably correct (I am not going to bother to check), but you are apparently not considering two factors:

1) If the fogger is inside of the greenhouse (as they are commonly installed) the input air will be a mixture of the air coming in from your vents AND the air from within the structure (with an ever-increasing humidity level).

2) Your assessment is also based upon 100% evaporation, and my experience is that at the higher liquid flow rates, the average droplet size from the fogger increases to the point that a fair amount of it does not evaporate.

[DavidCampen]

Originally Posted by raybark

I have studies psychrometry extensively, and understand it quite well, so your calculation is probably correct (I am not going to bother to check), but you are apparently not considering two factors:

Hello Ray, thank you for answering, it is so nice to have someone here to chat with.

I have a degree in electrical engineering and before that substantial training and experience in chemistry and chemical engineering. I don't recall that I had ever looked at a psychrometry chart before the other day, I had done my previous evaporative cooling calculations using first principles but I didn't have that notebook at hand and so looked on the internet and found the psychrometry chart. Using that chart is so easy that I will probably use it from now on.

Originally Posted by raybark

1) If the fogger is inside of the greenhouse (as they are commonly installed) the input air will be a mixture of the air coming in from your vents AND the air from within the structure (with an ever-increasing humidity level).

Yes, I had ignored that in my first level approximation that I had posted above but the configuration of my greenhouse is such that intake air enters at one end just before the Aquafogger and then exits via the exhaust fan at the other end; in between there should be enough mixing that the exhaust air would be near the assumed 80% humidity.

And of course another big effect that I had ignored is solar input.

Originally Posted by raybark

2) Your assessment is also based upon 100% evaporation, and my experience is that at the higher liquid flow rates, the average droplet size from the fogger increases to the point that a fair amount of it does not evaporate.

Ah yes, that is why I was curious as to what model you are using. The Aquafog 700 and its predecessor the 400 are by far the least powerful of the models. I am debating if I should instead purchase the Aquafog Turbo XE 330 model that uses a much more powerful motor and produces a finer droplet size. The XE 330 is about twice the price of the 700 but the considerations for me are that the Aquafog 700 is much quieter while the XE 330 produces a finer particle.

[raybark]

After 3 years of ChE school - where I was first exposed to the charts - I decided I didn't want to be a "plumber", so switched to Ceramic Engineering & Materials Science, where I was exposed to it again, this time as part of controlled drying of clay bodies. I later learned Ceramic Engineering is simply high-temperature chemical engineering anyway, and after 4 years of product/process development work for Corning, I worked in the chemical industry for 28.

I have the 700, but I don't think going to a larger motor for more atomizing power is the entire solution. I believe the larger units are intended for longer throw, so the selection should be based upon the size of the GH.

When the water is atomized, I think they all pretty much average about 40 µ droplet particle size. At low flow rates, they are ejected from the fan and disperse, mostly evaporating. As you increase the water flow rate, the density of the fog increases, so there is a greater probability that the droplets will coalesce and drip, rather than fog.

The Jaybird info even eludes to that, as for one of the XE models (I don't recall which one), they have a low-flow controller for "dry fog" applications, and larger ones for misting.

I suppose the real solution would be larger diameter to reduce the fog density, but that would be an entirely different device.

If you do get an Aquafogger, remove the safety grill from the front (they tell you to do so only if it's elevated and out-of-reach), as it accumulates a lot of the fog and drips heavily if you don't.