uc vs aeroponics

[Bobby Smith]

John-

What formula do you use for calculating how much a pressure tank can hold vs PSI in the tank? You mentioned a couple times a 4.4 gal tank can hold 0.04856 or whatever at XXXpsi. How can we calculate this ourselves?

Enjoy :)

http://www.engineeringtoolbox.com/expansion-tanks-d_885.html

 

[john guest]

LOL, thats too scary by half, Boyles Law is enough for most tank calculations :)

 

[Bobby Smith]

John, ordered the pressure relief valve so as I see it I'm just about done buying stuff.........should all be here by late this week or early next week, so don't make yourself scarce in that time frame :)

 

[frophead]

Thanks Bobby,

Now I admit I only made it through the 9th grade, and I don't much have a brain good at equations. I'm confused as to what formula I should be looking at on that page. Closed Compression Expansion Tank? Is that correct? That seems to make the most sense based on the short description. If it is, I can do the math part of it, but I am confused where I am getting some of the values...

So breaking it down:

Vet = k Vw [ ( v1 / v0 ) - 1 ] / [ ( pa / p0 ) - ( pa / p1 ) ]

where

Vw = water volume in the system (gallon, liter) <--1. is this the maximum capacity of the tank?

v0 = specific volume of water at initial (cold) temperature (ft3/lb, m3/kg) <--- 2. where do I get this value from?

v1 = specific volume of water at operating (hot) temperature (ft3/lb, m3/kg) <--- 3. Where do I get this value from?

pa = atmospheric pressure - 14.7 (psia) <--- 4. Is this just a standard value that doesn't change, kinda like pi?

p0 = system initial pressure - cold pressure (psia) <--- 5. Is this just the minimum pressure in the tank, aka the factory pre-charge?

p1 = system operating pressure - hot pressure (psia) <--- 6. Is this the maximum tank pressure? Or perhaps the desired tank pressure aka how much we are putting in?

It would be a huge help if you can clarify this for me. I would really appreciate it. I feel so lost. :(

 

[Bobby Smith]

4) Yes, for our calculations that number is fine (varies by altitude, but not enough to worry about).

As for the other five questions, I'd wait for JG to chime in because I'd just be shooting from the hip and guessing.........

 

[Jalisco Kid]

You should move the last 2 pages to another thread.JK

 

[john guest]

Its getting too technical guys :)

The thing to remember is the tank has a fixed volume (x gals) and water is incompressible. Using boyles law, you can calculate the change in volume of air at different pressures. All you need to know is the tank volume, the air volume at the cut-in pressure and air volume at the cut-out pressure. Any space not occupied by air will be occupied by the water.

 

[frophead]

Found a really good explanation of using boyles law to calculate this here.

Phew! That makes a lot more sense to me now. :)

John can you please check my math for me, as I believe this is correct:

This is assuming I am hand pumping a 20G tank to 110psi with a factory pre-charge of 10:

So essentially (10 + 14.7) x 20 / (110 + 14.7) = 4.45998445998446 usable gallons of nutrient solution in the tank @ 110 psi?

Thanks a lot I think I have a handle on this I just want to make sure.

 

[john guest]

almost! you`ve got the air volume. Subtract it from the tank volume (20gal) and you`re there :) If you work through Example 1 in your link, you`ll soon get the hang of it.

Its a good idea to make a spreadsheet to do all the calculations, much easier ;)

 

[frophead]

Ohhhh so in other words the real answer would be 20 - 4.45998445998446 = 15.54001554001554

So 15.54001554001554 = Gals of nutrient solution in the tank @ 110 PSI? Or did I misunderstand something...

Spreadsheet is a great idea. I'll whip one up after work tonight. :)

Thanks a ton man

 

[Bobby Smith]

Update - have the misters, fittings, prefilters (but I ordered a couple more of a smaller micron size) and relief valve.

Also put in an email to the company I got the timer from asking if they could send me the 110V instead - instead of trying to futz around with a car battery in there, figure I'll just get one of these and hook it up inline with the timer and solenoids - can run 500 watts for 5.5 minutes, so that would cover a few hundred/thousand cycles - that's enough insurance for me, and allows me to keep a car battery out of my grow.

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3612224&CatId=234

Still debating how many misters/solenoids to use.........currently planning on 30/4, but might step that up to 60/8 tonight..........depends on how much I have to drink.

 

[john guest]

Hi Bob
The UPS should give you 2-3 days grace, i couldn`t find the spec on the solenoids so i had to guestimate those but it does include the pump.
A similar 12v setup with a hydrostatic test pump will run for about 28 days on a fully charged 60A/H deep cycle battery or alternatively completely offgrid with the addition of a 20w solar panel to trickle charge the battery.

 

[Bobby Smith]

Update

Hi Bob
The UPS should give you 2-3 days grace, i couldn`t find the spec on the solenoids so i had to guestimate those but it does include the pump.
A similar 12v setup with a hydrostatic test pump will run for about 28 days on a fully charged 60A/H deep cycle battery or alternatively completely offgrid with the addition of a 20w solar panel to trickle charge the battery.

Thanks John; the UPS just seems like a simpler solution for a moron like me - one power source, and if the power is off for 2 or 3 days I've got more to worry about than dead plants.

So here's where I stand so far - solenoids will be here either today or tomorrow, as will the accumulator tank.

The fittings place fucked up and shorted me six fittings, so those will be here early next week.

So all I'm waiting on at this point is the pump, which will be here either Wednesday or Thursday, but I'm gonna try to start constructing the housing and setting up the shit I already do have this weekend and into early next week.

Oh, and I'm getting that 110V timer, so that should be here on Monday or Tuesday.

Gonna need some wiring help over the next few days - to give you an idea, basically gonna do my best to copy "Mr. Mister" from that gardenscure.com thread - it's post #355 (memorized :evilgrin0040:) if anyone wants to see it.

 

[MediMary]

hey john, this should be your avatar. :)

 

[john guest]

JG fittings are worth their weight in gold, they save a lot of time.
I`m not 100% sure but it`d be worth checking whether the carbon filter is likely to strip micro`s/metals out of the nute solution as they go through it.

 

[TightBush]

just wanted to run a couple things by you guys...i found this pump that is 200psi. Im waiting on manufacturer to find out the flow rates at different psi.



Also I am totally stumped over the aquatec ddp 5800. I have found listings for this pump in so many different rates it totally confusing





Here is my favorite one though, i just need more info on the flow rateshttp://www.labontemotorsports.com/store/ccp0-prodshow/DDP-5800.html

 

[Bobby Smith]

Not really sure what good a pump that large would do you - in doing some more research (after I bought it, obviously), it quickly became apparent that the accumulator is the biggest "restrictor" out there for pressures.

Doesn't do any good to have a pump that can go up to 200PSI if your accumulator can only handle 100PSI, you know?

The one that they're comparing it to (the Shurflo 8030-etc.) in the first link is the one I have (will have shortly) - goes up to 150PSI, cuts in at 115PSI, and was $127 delivered.

I think that's gonna be a better move for you, in all honesty.

EDIT: here's the data for the Aquatec 5800 - it's a weak little pump:

 

[john guest]

TB,
If you have a 16-bar accumulator 200psi might be useful otherwise not so much. 25-bar accumulators are available in smaller sizes but you run into problems finding pressure reducing valves that can handle 25bar at reasonable money.
The aquatec cdp-8800 are good little pumps, you`ll need an external pressure switch as they dont have one onboard.
The manual test pump is the most economical choice in the long run, unless you have a huge setup. The initial cost of the pump is offset as you don`t need any of the electric pump failsafes or control gear.

 

[Bobby Smith]

JG fittings are worth their weight in gold, they save a lot of time.
I`m not 100% sure but it`d be worth checking whether the carbon filter is likely to strip micro`s/metals out of the nute solution as they go through it.

Aww fuck..............it appears as though you are correct, and those filters will remove shit I don't want removed.

Meh, maybe I'll find something else to do with them...........so I would want a simple sediment filter, correct? Like this? :

system

 

[john guest]

$42? ouchy.
The cheapest option for dtw is to run everything through a 1micron bag filter before the pump puts it into the accumulator. Its about as easy as it gets :)
No housing, no plumbing, dirt cheap and machine washable.

http://www.mcmaster.com/#6835k34/=ap99bv

51595K51 is the same size as i use, 7" diameter neck x 16.5" long ($5).