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Old 06-25-2014, 10:15 PM
GpsFrontier GpsFrontier is offline
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Join Date: Mar 2009
Location: Lake Havasu AZ.
Posts: 1,855

Hello MontyJ,
Ya, I would agree the first thing to focus on is insulating the buckets and tubing for sure. But the second part is to cool down the inside of them, otherwise the insulation will only hold in the heat.

I know you "know what will work" despite the numbers, but do you really believe your approach, using only 100W can withdraw 8KW of heat?
I guess your not really familiar with swamp coolers. Find someone that is running one, and ask them if you can feel how cool the water in it is. I have already built two swamp coolers from scratch for my greenhouse, and the way they work is simple. The last one I ran last summer had a 40 gallon reservoir. That reservoir was nothing but a 45 gallon storage tote I got at wal-mart for about $15. It sat in full sun all day with no insulation or lid, and when the swamp cooler was running, the water temp was in the low 60's Fahrenheit, even when the daytime highs were in the 115 to 120 range.

Granted I was using a larger fan, a 20 inch fan. But that was because I was trying to cool the air inside the greenhouse (not the water), so I wanted a lot of air volume. In the case of the reverse swamp cooler, the focus is on a large "water volume" of cool water, not cooling the air. So you don't need as much airflow. Most Swamp coolers only have a small reservoir, but you can make it as large as you want (when you build it yourself). That cold water is what you'll use to cool the nutrient solution with. But even if you wanted to use the same 20 inch high velocity fan I used (like the one in the attached picture), it only uses 30 more watts (162) than the 10 inch inline duct fan.

While I like your enthusiasm, I'm from Missouri (not really!) and it takes a 2x4 whack upside the head sometimes for me to "get past the numbers", LoL.
I'm sorry, I didn't mean to whack you upside the head with a 2x4, I just wanted to let you know that BTU ratings are not all the same, and comparing apples with oranges doesn't work. Swamp cooler BTU ratings are air temp ratings, that's why they don't apply. If you want to figure BTU's you need to calculate heat exchange for water volume. It takes a lot more BTU's to cool water than it does for air. Also you can increase the BTU's of the reverse swamp cooler without using any more electricity, simply by increasing the water volume. If you want to calculate BTU's for the reverse swamp cooler, try this.

Using the last swamp cooler I built as the test subject.
First, calculate how many BTU's it takes to cool down 40 gallons of water from 110 degrees Fahrenheit to 64 degrees Fahrenheit. That's a good starting point, and how many BTU's I got for my 200 watts. Now double the water volume to 80 gallons. Now you have just doubled the BTU's using the same 200 watts.

Now take it another step. The pump I used is capable of 500 gallons per hour. To be safe because you'll most likely want to turn over the complete water volume about every 30 min, and taking into account for head height, say your turning over 200 gallons every 30 min. Using a 200 gallon reservoir, you have now increased the BTU's to five times more, using the same 200 watts. You can also easily change the amount of cooling pad surface area without using any electricity (watts), and you can also easily increase water flow with very little wattage. This is why I say don't get stuck on BTU's.
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