Aquafog fogger.

[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.

[DavidCampen]

Great, thanks for the advice. I will probably start with an Aquafog 700. It will be more than 9 ft. above the floor so I will remove the fan guard as you mentioned.

I do want a pretty much dry fog so I expect that I will be using the Aquafog 700 at much less than its max capacity of 3 gph. This may not meet my needs for humidification and cooling when working in tandem with my 2000 cfm exhaust fan. If I find that I want more perhaps I will add a high pressure fog system; I see that there are some on the market designed to deliver about 10 gph.

[raybark]

Have you considered a large "swamp cooler" or wet wall? Either of those would do a fine job of cooling and humidifying.

[DavidCampen]

Originally Posted by raybark

Have you considered a large "swamp cooler" or wet wall? Either of those would do a fine job of cooling and humidifying.

Thanks for the suggestion but ...

This greenhouse is built on an 11ft.X20ft, 2nd floor balcony/deck that is attached to my condominium. Both the city and the condominium association are very particular and have given me considerable grief. I spent in excess of $5,000 on architectural drawings and other fees just to get city approval. Some of the windows are more than 20 ft. above ground and inconvenient to access by ladder so I had the ridge board of the roof extended out a foot to provide an attachment point for rope so that I could access the windows via climbing rope but the condo association did not like that and I had to cut off the ridge board extension. The condo association also did not like my shade cloths etc.

So I am limited to equipment that is very discreet in external appearance; this precludes a wet wall and I do not want to waste interior space on a large swamp cooler. If the Aquafog fan is not enough then it would seem that a high pressure fog system is my only alternative.

The problem with high pressure fogger systems is that most of them are sized to delivery 60 gallons or more per hour which is far to large for me. I have found an Arizona company, Aero Mist, that makes a small pump system designed for 10 gph that would work for me or I could buy my own bare pump and plumb my own system.

[Kentucky]

David, nice thinking, but I'd think a little more. Actually I am one of Ray's "plumbers". I guess that makes him a bricklayer .

My GH clearly operates in a higher humidity ambient environment than yours, but it's also much larger and has a correspondingly higher peak than yours at 30 x 36 with a 16 ft peak. The GH company that designed and built mine considered (at my request) a fogger cooling system versus other choices. They had two other much larger GH's built with foggers. Both were about 3 times larger than mine and although I don't know the exact peak heights, I'm guessing about 25 ft. Neither of those is able to totally evaporate the fog (with higher pressure and thus smaller drops than you will get).

It's possible that in your low humidity it might work, but I'd be suspicious at your peak height which requires much more rapid mass transfer to the vapor phase than any of the ones above. Especially since that evaporation will be occurring at the higher humidity inside the structure. The need for cooling and for humidity are independent of each other. So if you turn off the fogger at some preset humidity, that might be exactly when you need the cooling and cannot get it because of wetting the plants.

I opted for a wet wall system because of the fogger issues that resulted in wet foliage in more favorable conditions (bigger houses) than mine and much more favorable than yours. You can't just look at the chart to determine the outcome. The evaporation must occur in a limited flight time of the droplets and that's much more difficult to calculate (actually it's darn near impossible considering the range of variables that would need to be included).

The results from constantly wet foliage are devastating. Supplying sufficient RO water to meet your anticipated needs is also questionable and definitely expensive. I would be sure that that you are looking the output capacity of the RO systems you are considering, not the water input capacity. Confusing those two could be a mistake of a factor of three or four.

Water is cheap where I live. I can't imagine what your cost would be in southern California. I use rainwater with one of Ray's RO units as a backup which I fortunately don't need very often because I see dollar signs running out in the field every time I turn on the valve. I have his 100 gal/day (input) unit from which I get a measured 30 gal/day output of pure water. It has saved me from time to time (like the last two months), but I sure hate to use it. My water bill is about $40-50 a month higher with it running. I'm guessing it's actually running about 120 gal/input. It supplies a non-pressurized storage tank and operates on normal water system input pressure (about 60 psig) although that varies on distribution system usage rates.

In my experience, I do not think the fogger system will work as you wish and the water supply is going to be extremely expensive. Rigging up a way to use a wet wall would be a better alternative in my opinion.

Just a "plumbers" opinion.