PWM DC Pumps and Water Chillers for plate column cooling

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PWM DC Pumps and Water Chillers for plate column cooling

Postby moonshinindawg » Thu Nov 05, 2015 10:20 am

Hi gents

I guess I will start this off by explaining my other hobby, coral :)
I propagate soft corals and trade them all over aus it's heaps of fun and great for the stress levels.
I recently put a new all in one system together based on a constantly changing random flow system
Essentially the tank is fed from 2 pumps that are constantly varying in speed and the algorithm I use keeps each pump independently random which the coral seem to like.

Im using these http://www.fish-street.com/jebao_dct_water_return_pump obdviousley a little weaker then what some of you are running on your stills, but these new DC pumps are crazy

How does 15000lt/H + 5.2mt head @ 150w sound? up to scratch?

These pumps are amazing because the speed can be controlled just like a PWM fan with 1 little wire to an arduino/other MCU

So I guess I should also say I work in a lab and we do a lot of solvent extractions, all our distillation apparatus and rotovaps are cooled using chiller units, they dont have the same kind of energy put into them as a big ol copper still but the low volume chiller systems seem to run hard with a lot of head room. 1 unit we use is about half the size of a bar fridge and runs about 10 small glass columns at the same time (keep in mind the total volume of solvent being distilled even between 10 setups is <1lt) but I dare say it could handle much more.

Now these lab chiller units are basically the same as aquarium chillers which you can pickup off gumtree for $100 lotta the time the thermostat is fucked but that's perfect for us anyway.
here is a picy of an aquarium chiller
Image


So what I have been thinking about is this

Image


Similar to the current standard everyone uses on their plated columns but instead of a valve to control the flow rate through the RC I have replaced this with a variable pump (due to simplicity to control)

So I will use the arduino PID library and some other things to measure the RES temp and RC out Temp and keep the flow rate and water at appropriate levels, could also add controls to adjust reflux etc.
For the moment I didn't really see any use in changing the flow rate on the PC, so it's probably easier to drive separately with another pump

Ill try explain more in a bit just getting this out of my head and down somewhere, also nice to get an opinion or too :)
moonshinindawg
 
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Re: PWM DC Pumps and Water Chillers for plate column cooling

Postby warramungas » Thu Nov 05, 2015 4:57 pm

That's a pretty big load of heat you're going to be throwing through a small aquarium/lab chiller. Would it be up to a task like that once the water in the reservoir starts to heat up considering its usually only messing with a few degrees difference in/out?
The rotovaps usually only run around 50ish degrees depending on the solvent which is not a huge ask for a chiller unit. It would only transfer a tiny amount of heat into the coolant through the glassware especially if its doing less than 1 liter a throw of something like alcohol which has a pretty low specific heat capacity and a low contact time.
I'm just thinking what can happen to a fridge if you put a big ol pot of boiling water in it.
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Re: PWM DC Pumps and Water Chillers for plate column cooling

Postby timboss » Fri Nov 06, 2015 9:14 am

Hey mate, I tried cooling 200l with an aquarium chiller I had laying around, didn't work very well and quickly lost control of the temps.

Controlling the RC with PWM pump is an awesome idea though, to the point I'm going to have to buy one of those pumps!
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Re: PWM DC Pumps and Water Chillers for plate column cooling

Postby moonshinindawg » Fri Nov 06, 2015 9:38 am

How many horse power was the chiller
They make these puppies pritty big

I can link to the jebo 3 pin cable if anyone needs to make up a controller lead, very easy to set the speed on an Arduino if you can wrap your head around everything

With an 8bit controll signal there are 255 steps and you can get more with a 12bit controller therr can be 4096


I'll do the math and find how big a chiller would be needed.
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Re: PWM DC Pumps and Water Chillers for plate column cooling

Postby res » Fri Nov 06, 2015 6:00 pm

Interesting idea mate, very novel. The use of a pump to control rc temp seems very elegant compared to the more common solenoid on off approach.
Unfortunately for me I don't know a thing about arduino :doh:
Could you use a PID maybe? Don't know anything about them either but they seem more approachable 8-}
Good luck with it, cheers for idea. :handgestures-thumbupleft:
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Re: PWM DC Pumps and Water Chillers for plate column cooling

Postby moonshinindawg » Sun Nov 08, 2015 12:25 pm

Well the pump comes with a controller to change the speed, but its limited might be enough range to work.
The interesting part is changing over time for small adjustment these pumps would play nice with that ;)

I believe they work with 5v pwm logic but might need to level shift to 10v - (I think this is only for some non jebao brand pumps)
moonshinindawg
 
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