Aquafog fogger.
 

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?

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

There are several factors that could lead to a true 30 gpd from a 100 gpd system:

1) your input pressure at the system is nowhere near the 60 psi level you think it is

2) The water temperature is quite cold

3) You have a restriction somewhere.

I would speculate all of the above, as at 60 psi and 45°F water, you should still get 40!

Ray I know us chemical engineers are not too smart but I can read a pressure gauge. My city nominally supplies water at 80 psig, but I'm pretty far out on the system and my gauge varies from 50 psig during high usage times to 70 psig at night.

I have measured the output repeatedly with a can and a stopwatch since getting the unit over two years ago and it's 30 gal/day everytime...winter,summer,day, and night. I recently changed the RO element and guess what...30 gal/day brand new. There are no restrictions. It sits right next to the 250 gal. atmospheric pressure storage tank. It's supplied with a one inch water line and all internal and discharge tubing is that supplied with unit. The waste water tube dumps into a one inch pipe that carries it outside.

Anyway, I'm not complaining about the RO unit. I'm commenting on the fogger design that David is contemplating. He is looking only at the
ultimate evaporation (and humidity and cooling) attainable based on the humidity chart and not considering that mass transfer is a rate process dependent on the drop size and surrounding temperature conditions. He has limited height (and thus time) to get the necessary heat transfer into the drop and evaporate it completely before it reaches his foliage. The system is in reality its own worst enemy because both the increased humidity and reduced temperatures achieved by running it increase the difficulty and time required to evaporate more fog. Calculations can only provide a starting point for a system design. Unfortunately, testing it is the only way to completely evaluate it. I'm telling you that two systems much more likely to succeed that the one David is talking about (based on the inlet water pressure drops and water drop flight times available) fail to operate adequately and the GH designer has involved the fogger manufacturer to attempt to resolve the issues without success. As a result they essentially refused to install a fogger unit in my GH (unless I took full responsibility) and suggested the wet wall instead. That's cause for concern on David's part.

My only issue with the RO is that if he actually uses the water he is talking about it's going to cost an arm and a leg. I'm no where near California (Thank God), but I read about water usage restrictions there. I have no idea whether these effect him or not. I assume he knows the answer to that. I also do not not know the cost of his water, but it could not possibly be less than mine...at least I hope not. That would be a kick in the head.

I'm just letting you know that you have not properly considered all the variables in a fog system. Certainly whatever you do is up to you, but I assume you would not have posted the issue here unless you wanted some feedback. I'm apologize for ever mentioning Ray's RO system. What I get is what I get, but I assume that designing various chemical process systems over the last 40 years qualifies me to measure water flow while taking into account the controlling factors in that measurement. 30 gal/day is enough for my emergency use. I'm not complaining, just stating the facts.

Other than that ...How 'bout them War darn Eagles!!!

1) Most folks don't have gauges, so I wasn't expecting that.
2) Most folks have more along the lines of 35-45 psi water.
3) I assume you replaced the pre-membrane filters too, so now I am baffled.

I have the same manufacturer's 100gpd system going into an atmospheric tank in the GH, and I get about 50-60 gpd routinely. I also have a 60 gpd unit with bladder tank in the house, feeding the fridge for ice and water, but it also has a permeate pump, so i don't know it's output.

PS: I grew up in DC, so you know my football issues.

The foggers that I am considering operate at pressures of 500-1000 psi and produce droplets in the 10-40 micron range. The Los Angeles County Arboretum has a high pressure fogger like this in their begonia (and Nepenthes) glasshouse. It produces an extremely fine fog that hangs in the air for minutes. Still, I concur with you observation that if it is operated for the lengths of time required for cooling, several hours continuous, that the plants will get wet but there will also be at least 18 hours in every 24 hour cycle that does not require use of the foggers for cooling where the plants can dry.
I understand that the feedwater input requirement is much more than the product rate. I have not confused those. When I say a 200 gpd system that is the RO water production rate. With a standard 1:4 product:brine ratio such a system would require 1000 gpd of feedwater. That is why I hope to be able to reduce the product:brine ratio to close to 1:1.

Everyone else rates systems on production rate not input rate, as the flux across the membrane is characteristic of the system while input rate depends on only the selection of brine restrictor.

That would be a low 3:7 product to brine ratio. Unusually low for a standard home system. It would be very interesting for you to measure your actual product:brine ratio.

"The Los Angeles County Arboretum has a high pressure fogger like this in their begonia (and Nepenthes) glasshouse. It produces an extremely fine fog that hangs in the air for minutes. Still, I concur with you observation that if it is operated for the lengths of time required for cooling, several hours continuous, that the plants will get wet but there will also be at least 18 hours in every 24 hour cycle that does not require use of the foggers for cooling where the plants can dry."

Go for it. I don't have sufficient information about your plan to comment any further. I visualize the LA County Arboretum that you mention above to be a very tall, high volume structure like others I have seen. I don't know that as I've never been there, but if you are comparing a 30 or 40 foot tall structure to a 10 ft wide GH with a peak of maybe 12 ft I think you are comparing apples with peanuts...but I have no idea what the LA structure or its system is like so I should shut the heck up.

I also don't understand your statement that the system will be only be required 6 hours every 24 for cooling. The only thing I know for sure about your climate is that its much different than mine. I frequently have to cool 24 hr. a day for days on end. It seems to me that you are saying that you plan to use temperature control on the fogger (not humidity control). So a lot of the wet foliage result will be dependent on how fast the foliage drys after the system shuts down. What I can say with some reasonable confidence is that if the foliage stays wet for periods of 6-8 hours, especially if it's frequently, you will have fungus issues. The problem with fungues is that the more you get, the more you get because they are sitting there spewing spores whenever the conditions are right (usually wet and cool).

Once again, I don't know enough about your system and environment to really be commenting. I'm just offering you some cautions that apply generally to greenhouses for your consideration.

Thanks for the cautions about fungus.

Yes, my plan for environmental control of the orchid house is peculiar to the Mediterranean climate of Southern California and especially the Los Angeles area where I live. I am less than 30 miles from the ocean to the west and 20 miles from desert to the east, I am separated from the desert by mountains. In late summer and early fall when it is hot this is only in the afternoon with cooling from an onshore flow from the ocean in the late evening. In early fall there is sometimes a desert wind that maintains the heat all evening but then it is also extremely dry, 10-20% RH, so that I can get significant evaporative cooling while still keeping the greenhouse humdity around only 50% RH.

For my cooling scheme I plan to control the exhaust fan proportional to a temperature setpoint. The humidifiers will operate according to a humidity setpoint which I would increase on hot afternoons and then set lower in the evenings.

Edit:
For example, just now at home, November 4th at 3:00 PM, the temperature is 95 deg F with 12% RH.

"For my cooling scheme I plan to control the exhaust fan proportional to a temperature setpoint. The humidifiers will operate according to a humidity setpoint which I would increase on hot afternoons and then set lower in the evenings."

I see. I'm going to interpret your words above in strict control system language as opposed to everyday dictionary language. I believe that's what you mean.

Proportional control of the fan(s) (for the uninitiated) is just on/off control with a gap between on and off setpoints to avoid control system instability. It's pretty much the same as your home furnace control and much less complex than deviative and integral schemes, but cheaper and much more common in non-industrial use. In effect it will just turn the fan(s) on and off when certain setpoints are reached. Derivative control takes into account the rate of change of the error signal and integral control takes into account the area under the time/error curve. All three together are super good but expensive to implement.

It appears to me that, unless you left something out, operating the fans on temperature control and the foggers on humidity control, will at times allow fogging without the fans running. Depending on the location of the humidity sensor, this could quickly shut off the foggers or maybe not. Nonetheless, operating the foggers with no fans decreases drop flight time and evaporation rates increasing the likelihood of rain in the GH. But as I said before I never see humidity like 12%. Looks like you could operate the foggers on humidity control, but also turn them off when the fans stop without much effort at all.

Looks like you are dropping a lot of money into this effort and I wish you the best. Believe me I worried about my own design choices when I dumped over huge bucks into my GH. Fortunately most of it worked well. I hope you get the same result.

Yes, I have a Phason MT4C proportional fan speed controller that will vary the fan speed from an idle setting at the temperature setpoint to full speed at 6 degF above the setpoint. The controller can be configured so that at 2 degF below the temperature setpoint it will turn off the exhaust fan or it can be configured to always run the exhaust fan at the idle speed setting when below the temperature setpoint deadband. I will probably use the Phason controller in the configuration that always maintains idle speed below the setpoint and add an on-off controller that will remove power from the Phason (and thus completely stop the exhaust fan) when I approach my heating setpoint.
http://www.phason.ca/mtc4c.htm

No, I will be using an Aquafog humidifying fan as my first level humidifier.
http://www.jaybird-mfg.com/Directfeed_desc.asp
If I add a fog nozzle system it would be configured as a supplement to the Aquafogger so I would always have the Aquafogger fan running when humidification was active.