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Cooling the Nutrient Solution


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  #1  
Old 06-26-2010, 03:59 AM
omerizm omerizm is offline
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Default Cooling the Nutrient Solution

I need to cool down my NS. It peakes at 30 degrees celcius in very hot days. I grow lettuce and recommended temp is 24 C.

I'm thinking about using the return water from the cooling pads, which runs at 20 degrees.

The idea is, put a pump in the cooler tank, pump it through some tubing insterted in the nutrient tank, return heated water back to cooler tank. Use a thermostat to maintain temp. What do you think?

And, can I use copper tubing? Will it do any harm to the plants? If yes, what else can I use?

Thanks in advance.

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Old 06-26-2010, 06:15 AM
GpsFrontier GpsFrontier is offline
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I am not sure what the cooling pads are, or how much liquid it circulates. But coils in the solution or visa versa may work. To be honest I am not sure if copper coils would react with the nutrients at all, although it might add excess copper to the nutrient solution. You can also use stainless steel tuning (very expensive), or any poly tubing (the smaller diameter the better). Although metal will give much better heat transfer. If using poly tubing you may need as much as 3 times as much as metal tubing for the same results.


P.S. If you had a link to the coiling pads that you were planing to use, and a simple diagram how you plan to use it, I could possibly help with refining it.
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Old 06-26-2010, 07:10 AM
omerizm omerizm is offline
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Its the water coming out of the evaporative cooler pad. The circulated water that wets the pads is always cool, about 20 C. Theres as much cool water as the nutrient solution so it will be enough.

Here's an example of an evaporative cooler pad: http://www.rotorsource.com/images/evapcooling/illus.jpg

I'm sure it will work with enough tubing but I have worries about copper. As you said plastic is very bad for conducting heat. And stainless steel is very hard to bend into a coil shape like this:

http://www.advancedtubular.com/wiki/...il_65pitch.jpg
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Old 06-26-2010, 07:40 AM
omerizm omerizm is offline
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Or maybe aluminum tubing?
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Old 06-26-2010, 08:26 AM
GpsFrontier GpsFrontier is offline
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I saw the link for the what you call the cooling pad. It looks like nothing more than a filter/pad for a swamp cooler. The pad/filter does not cool the the water, it actually heat's it up. If you run it through your coils before it gets to the top of the pad and drips down through the filter you may have a chance. But I'm not sure how much volume it can do. At 20C, 68F you will need a large set of coils as well as volume of liquid going through it to even help. Keep in mind, if it's in an enclosed system the coils will heat it up as well, further reducing it's effectiveness.

I'm not sure where you have your system but I would use a geothermal heat exchange system, if I can at all run the pipe/tubing outside. Either as a closed loop, or open loop system. Although I think a open loop would be the most cost effective even in the long run.

As for aluminum I am not sure if it reacts any different to the nutrients than copper. Stainless steel is the only metal that I would be sure of. I don't remember what department it was in but they do have them already formed in coils, they were just too expensive for me to consider.
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Old 06-26-2010, 09:30 AM
omerizm omerizm is offline
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Yes you are right, its the kind of pad that is used in swamp coolers. They are commonly used in greenhouse cooling.

http://www.igcusa.com/greenhouse_coo...nformation.htm

The water dripping down the cooling pads is cool, actually it is equal to the exit temp. of the air.

For example, right now the outside temperature is 33, the temp of the air leaving the pads is 22, water in the cooling tanks is 22 as well, and the temp in the middle of the greenhouse is 26. The nutrient solution is 27. (all in celcius)

This is a 15 meter square hobby greenhouse in my terrace, I am not on the ground. I am in Europe, so don't worry about the name of the department, we probably don't have it here anyway.

It is true that since the temperature diff. is small, I need a lot of tubing and flow rate.

I will look for steel tubing formed in coils.

Thank you for your help.
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Old 06-27-2010, 09:26 AM
joe.jr317 joe.jr317 is offline
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I use ice sometimes. I also have the reservoirs insulated some. Not much, though. I put a half gallon plastic jug of water in the freezer overnight and put it in the reservoir in the morning. Unfortunately, this is not an ideal way to do things. It is obviously not going to be constant and takes up freezer space. But, it may help while you are looking for a more permanent solution.
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Old 06-27-2010, 11:57 AM
omerizm omerizm is offline
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Thanks Joe, as you said it is not a permanent solution but it will help till I find one.
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Old 06-29-2010, 01:20 AM
watercatwn6535nd watercatwn6535nd is offline
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Default cooling and parts

I have used copper back in the day in my nute system and never had issues. it turns green and oxidizes but no issues i have ever saw.

i build nute coolers. i buy used wall shaker air conditioner on Craig's list for cheap that work. Then on ebay i buy stainless plate heat exchangers. you get order them in what ever pipe size you want. i cut the evaporator and condenser off the units and install the plate exchangers in there place and recharge with a cheap can of r134. it only takes a smidge of the bottle and a a/c shop should be able to charge it for you for cheap.

I then take a poly 55 gallon drum and install a small pond pump in it and fill it with water then flow that through one plate exchanger and the nutes through the other and you have what would be a very expensive chiller for $200 bucks. the drum has enough surface area if its in the shade outside it will work perfectly. i had two 20 btu wall shakers heating a hot tub for a few years with a pond pump circulating it and it maintained 120f in freezing weather and super hot in the summer we had to install a car radiator on it with a fan and therm o fan switch. so surface area is what the tank is all about.

if you only install a exchanger o the nute side for cooling you will be able to still use the fan and a/c system as a air to water and if your real care full pull the temp prope off teh front and un coil it to stick it in your nut tank or tape it to the input line of the nutes and wrap it with insulation and the unit will turn on and off at the temp you set it at just like it was doing a room and you can install it right in a window just like it should be.

Or a extreme igloo cooler from wall mart and make your blocks of ice to keep the cost down and run lots of copper line in it and just let your current system flow through it. i've been there before. ice is always your hydro buddy. 1 for your hydro system and 2 cubes for your margarita while you sit and watch over the grow in that awful heat. 5 ft of copper in ice water is amazing on a small pond pump. also find a car heater core thats is aluminum and plastic and install a couple or one large PC fan on it and leave it running. every btu counts or makes your ice last longer.
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Old 06-30-2010, 12:30 AM
widespreadpanic widespreadpanic is offline
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Default aquarium chiller

I have had many people recommend burying your reservoir and or creating some form of "geothermal cooling" by using buried coils with a pump.

I myself found a used aquarium chiller from someone breaking down an aquarium and bought it for 150 bucks. I can manually control my 55 gallon reservoir to seemingly any temperature from 55 degrees upward. I keep my tomato nutrient res. at 67 degrees.

It may be more expensive than other methods but the reliability and programmable nature of the chiller has been great for me. I am a new grower however, and others surely have better/cheaper alternatives.
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Old 06-30-2010, 02:04 AM
GpsFrontier GpsFrontier is offline
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If you can find a used (cheep) aquarium chiller that could defiantly be a possibility. The new aquarium chillers that I found on-line last summer started at around $300 (if I remember correctly), and were only designed for 15 gallons, they just went up in price from there. I have no experience using them so I wouldn't be able to tell how well they work outside in temperatures like the 120 degree days we have here. I image a rooftop or terrace could reach that temp as well.

P.S. I designed a cooling box a while back that will help keep the heat from the reservoir. It's basically just a large ice chest. I have yet to build it, but plan to hopefully this summer. I attached some pictures, but I have complete directions in a pdf file. I designed it for two 32 gallon trash cans for reservoirs, but it can be built to any shape or size. The inside needs to be kept cool, I can think of a few ways to do that, including an aquarium chiller. It may give you some ideas.
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Old 06-30-2010, 10:04 AM
omerizm omerizm is offline
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Thank you all for the ideas & suggestions.

I had mixed comments about using copper and today I decided and bought stainless steel tube. 7.5 mm diameter, 0.40 mm thickness, 6 meter long. I guess it shouldn't be hard to bend since it is very thin. It cost... let me convert... 6.7 USD. Is life getting any better than this?

As I mentioned earlier, I am planning to use the water from the evaporative cooling unit to cool down the nutrient solution, since it is a source readily available. If I did not have that, then I would consider using some sort of vapor compression refrigiration unit such as a 2nd hand aquarium cooler. Note that this would cost a lot more to buy and operate, since it would consume much more energy.

Now I need to bend the steel tube into a coil form. Also I need a small pond pump to circulate the cold water through the tube. I will use a thermostat that I already have to keep the solution at 22-24 degrees celcius. I will post the results.
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Old 07-01-2010, 06:41 AM
GpsFrontier GpsFrontier is offline
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If you found 18 feet of stainless steel tubing for $7 USD, I am impressed. Even if you still need to bend it, for that price I will buy the tool to bend it (I have a tool, but only for bends, not coils). What I found was around $40 USD and I doubt it was any more than about 8 feet stretched out. I can get 700 feet of 1/2 inch poly tubing for $40 ($39.95+tax).

Just a note on the water temp of the evaporation cooler. I had bought a large portable one to cool my room with, I sold it because it just drove up the humidity in the house, but that was not my point. When I first bought it and brought it home I also got 20 lbs of ice. The cooler held about 5 gallons of water, I dumped all 20 lbs of ice in the water reservoir, then filled the rest with cool tap water. It felt just like an air conditioner (as I imagined it would). That lasted for 20-30 minutes before the ice had all melted and the water was almost at room temp (about 75 degrees F). It cost about $3 USD for the 20 lbs of ice, I quickly found it would be cheaper to run the AC. But that was just my experience. If the water line going in is directly from the the household pipes the temp might be because of the geothermal effects of the underground lines (sounds like the right temp). But you know your system, and how it's set up.

P.S. Pictures would be nice also.
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Last edited by GpsFrontier; 07-01-2010 at 06:59 AM.
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Old 07-01-2010, 06:29 PM
omerizm omerizm is offline
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Bending the tube turned out to be difficult without proper tools, so I asked a friend to do it in his toolshop. I hope to have it by tomorrow. I will post pictures.

Let me explain how I have cool water with this evaporative cooler setup. (I find this difficult because English is a second language to me, please forgive me if it does not make sense to you.)

I think you know the concept of evapotative cooling, but I will start with that anyway. Evaporation process requires energy. So as the water evaporates, It takes energy from what is nearby. As a result what is nearby cools down.

So, you want to cool the air. In order to do that, you force air through a pad. You keep the pad wet, so as the air passes by, some water evaporates and draws heat from the air. To wet the pad, you pump water from a reservoir and let it drip on to the pad. The excess water drips down the pad. You collect that water and return it to the reservoir to use it again. So it is a closed system. I don't use the water from the household pipes.

Now this water that is circulated through the pad gets cold in time. It gets down to the exit temp. of the air. Because energy is drawn from the water itself as well as the air passing by. I'm gonna use that water to cool down the nutrient solution. And It will be always cool as long as the evap. cooler oparates, It won't get heated up.

The evap. cooler should always draw fresh air from the outside and that air should have a low relative humidity. If the relative humidity of the incoming air is high, very little or no water will evaporize and thus, no cooling. If you can not get cool air without putting ice in the water, than you are evaporizing no air. Maybe your incoming air is too humid already?

Here is a chart. For example, let incoming air be at 90F. If RH is 10 percent, the air leaving the pad is 67F. And the continuously circulating water will be at 67F as well. But if the RH is 70 percent, than air leaving the pad is 84F, only 6 degrees cooler:

http://www.alloutcool.com/image-file...art458x298.gif
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Old 07-02-2010, 05:02 AM
GpsFrontier GpsFrontier is offline
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Love to see the pictures when you get it done, I'm also interested in how well it works for you. Ya I am familiar with evaporative coolers, although I commonly call them swamp coolers. That's an interesting chart, and I have not done extensive testing on them, I'm just going by my real life experiences. This is the portable cooler that I mentioned I had (before I sold it) although I only paid $299 USD at the time.

Master cool

Although technically it's a closed loop system, they still lose water. It evaporates and becomes humidity in the room. As I mentioned it held 5 gallons, but the water level would get to low for the pump if you ran it full blast for 3-4 hours. I didn't want the pump to run dry while I was sleeping so I hooked up the water line to the float valve (it came with) to a faucet (for the toilet tank fill line) in the bathroom and ran it along the baseboards into the bedroom. Now I know it is not suppose to work well in closed spaces, but I was not about to open the windows and allow the 120+ degree heat (fresh air) into a room that was 80 degrees without the cooler even being on.

Of coarse it felt cool if you were right in front of it, but the humidity in the room kept rising (because the water evaporates) to over 60% (from less than 10%). That's why I sold it. At my place of work we had two roof mounted swamp coolers in the shop, and from my experience they still weren't any good unless you were standing directly under the air duct. If you were 10 feet away it did no good for me. I don't know what the water temp was in those systems, but being mounted on the roof and the water lined needing to run up there, it was not any 72 degrees. But all that being said, I can easily build a swamp cooler myself. I have no idea what the books say the temps should be, but I do have real world experience with how they function, work, and cooling ability's (in my area).

I also planed to build something similar, but an actual closed loop design that's more like an AC, than swamp cooler. Because the water does not flow down a filter that the air passes through providing humidity. Instead the water is pumped through a radiator (refurbished, and clean), and the air passes through the radiator. The water would be pumped from an ice chest full of ice water to cool the radiator.

No humidity and cool air. But I have never tested it, and don't know how long the ice water would stay ice cold. As you mentioned it takes energy to cool with a swamp cooler, as it would in this system. That energy is heat transfer (same principal as geothermal energy). But the key is "transfer" not "elimination", so the heat does not disappear, it's just transferred to the water. I know that's slightly different than how a swamp cooler cools, as anyone who has walked under a mister on a hot day knows. But that's because technically it's not a completely closed loop, and the air passes through the water on the filter.

If the air temp and water temp are the same or close then there is not much transfer, but in my area when the outside temp is 120+ degrees there is plenty of transfer. We even leave the hot water heater off all summer because the heat in the garage is hot enough to heat the water in the hot water heater, and that's insulated. We even need to let the shower run (cold water) for about 10 minutes before getting in it because the water is to hot. After about 10 minutes the water that was in the underground pipes (and cooled by geothermal energy) begins to flow out, then you don't get burned when getting in it.

P.S. Sorry English is my only language, but I believe I am able to understand you fine, for what it's worth.
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Old 07-02-2010, 04:17 PM
omerizm omerizm is offline
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Here is the coil. I put a pencil too so you can compare the size.



I will post pictures when I complete the setup.
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Old 07-02-2010, 07:03 PM
GpsFrontier GpsFrontier is offline
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He did a nice job getting the coils close and even.
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Old 07-07-2010, 01:14 AM
pec0054 pec0054 is offline
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Default How about coils and a small drink refrigerator

I've been thinking about running some water or other cooling solution in coils in my reservoir and pumping it through a small Dorm Room size refrigerator, like something I could pick up on ebay or craigs list. Not sure how I would control the temp to keep it from getting too cold though .

Last edited by pec0054; 07-07-2010 at 09:08 AM.
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Old 07-07-2010, 09:15 AM
pec0054 pec0054 is offline
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Quote:
Originally Posted by GpsFrontier View Post
The inside needs to be kept cool, I can think of a few ways to do that, including an aquarium chiller. It may give you some ideas.
I think a real cheap A/C window unit made into a "window" in the side of the box might work well for cooling the box and contents, plus it has a thermostat control, who knows, you might even find one with a remote ;>)

PC
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Old 07-07-2010, 11:57 AM
omerizm omerizm is offline
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Here are some photos of my setup:


Water tank of the evap. cooler.
There is a float valve attached, orange ball.
Two pumps inside.
Black pipe runs water to the evap cooler.
White pipe is the return from the evap. cooler.
Blue pipes are used to circulate cold water through the coil, which is inserted in the nutrient solution tank.



The fans, NFT channels and a small raft system for the seedlings.



The evap. cooler.
Black pipe runs water from the cooler tank.
White pipe below returns excess water to the cooler tank.




Nutrient solution cooling setup.
Blue pipes are used to circulate cold water through the coil, which is inserted in the nutrient solution tank.
A thermostate is used to stop the pump when NS colls down to 25 degrees celcius.

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