Condenser cooling

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Condenser cooling

Postby headshaker » Fri Jan 12, 2018 6:45 pm

I have watched several demos on reflux stills,and I often see them turn down the water to add reflux.My question is (how do you control your flow,and about how much flow do you need)?If seen temp gauges on the input and output also.My beer set up comes from my pool to a hot pressure washer coil to a 50 ft work coil .It can take down beer in about 10 mins.Would that be to much?This is an open system at full pressure around 35 psi.Is this to much pressure to crimp off some on my pump?
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Re: Condenser cooling

Postby still_stirrin » Fri Jan 12, 2018 8:00 pm

A swimming pool is a “over the top” water reservoir. It would be fantastic for running a still. Go ahead and run your pump up to 35 psi discharge and it will feed the condenser(s) just fine. But put a valve on each of the condensers’ coolant outlets so you can regulate them independently.

Your quetion regarding adjusting the reflux condenser’s coolant flow to manage the reflux suggests you’re looking at a CM column. In fact, the CM’s are the most tricky to operate. LM’s are easier and more stable. And VM’s just about regulate themselves...once set, you just collect the product until the tails at the end when the flow simply stops.

So, it’s hard to answer your question without a little bit more info on your setup. Whatcha’ got?
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Re: Condenser cooling

Postby Yummyrum » Sat Jan 13, 2018 3:15 am

headshaker , how much water flow you need will depend on the amount of power the boiler is supplying , the temperature of the cooling water and the efficiency of the condenser itself .

Like still_stirrin said , sounds like you are referring to a CM type reflux head . CM reflux condensers are touchy things to drive . I use one on my 4" plated column . The realistic flow through it is really stuff all . I use a 1/2" 5 turn needle valve to adjust it and at the typical operating point , I'm about 1/4 to 1/2 a turn from closed .
All I use is a Submersible pump in a 2000 liter tank .The pressure is not that great but I still have way more pressure and flow available than I ever need .

A few guys use thermos on the inlet and or outlet cooling lines . Those that use them say they are useful . I and the majority don't use them .
The thing is when you adjust the needle valve , there is a period of time often several minutes before you see a change in the product flow rate . .... due to the thermal mass of the condenser .Adjustments need to be done extremely small and a period of time needed to observe the change before tweaking again .....otherwise you are chasing your tail .

I ended up putting a Ball valve across my needle valve so I can quickly switch from full reflux to taking off product without having to spend ages fiddling around .
Here it is on my 4" 4 Plated still

Bypass.jpg


I use the same CM condenser on my 4" packed 1 meter column

Needle valve.jpg


Now one real difference between CM and VM ( or LM ) is that water pressure variations on a CM will cause heaps of grief whereas on a VM or LM it will not be such a drama .
My first ever still was a Little CM still and being on tank water with a pressure pump , the thing would surge and stall as toilets were flushed and washing machines ran ....it didn't take me long to rig up a tank a few meters above the ground and gravity feed the still .......again this gives you an indication of how little pressure or flow is required to run our stills .
And I don't use the nylon hose on the output any more ...it got a copper update :oops:

SS Reflux still on 5 liter boiler.jpg


I built a 2" VM/LM reflux still and I still use it but only in VM mode . VM is so easy to drive and has nothing really to do with cooling flow rates . So long as you have enough coolant flow to get full reflux you are golden . I think from memory mine was around 1 liter per minute ......not a huge amount .
Incidentally , If I started the pump to prime the condensers and hoses , if I switched off the pump it would work through siphon effect if the output hose was draining down into the lower house tank ....again that gives you an idea about how little water is needed :thumbup:

VM-LM running.jpg


I converted it to CM for a while but the Condenser I built was way too small and it couldn't handle the power from my boiler so Runs took a long time at reduced boiler power .
I also used a ball valve to control coolant flow but it was a super touchy thing and I should have used a needle valve .
Eventually I converted it back to VM :thumbup:

2 inch  RC shotty.jpg

VM-CM mod.jpg


Another thing to think about is that the Product condenser also uses water but it is usually only a fraction of what the Reflux condenser uses but it add up .

So basically if you can supply around 2-5 Liters per minute then you will have it covered for the typical stills that we use .
If you go CM then you must have a constant stable pressure .......Gravity feed works well
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Re: Condenser cooling

Postby headshaker » Sat Jan 13, 2018 7:47 pm

Man you guys have amazing rigs.
are your pumps pressure compensated ,so when you slow the flow is doesn't hurt the pump?
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Re: Condenser cooling

Postby cede » Sat Jan 13, 2018 7:56 pm

Magnetic pumps do the trick :)
In fact, magnetic pumps are easy to regulate. Just put a valve on the return line.
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Re: Condenser cooling

Postby acfixer69 » Sat Jan 13, 2018 8:00 pm

Quick answer is unless you are using a positive displacement pump most if not all circulating pumps are fine like when you put your hand over a vacuum cleaner hose it rev's but amp draw goes down that is cause it's doing nothing layed off

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Re: Condenser cooling

Postby still_stirrin » Sat Jan 13, 2018 8:06 pm

headshaker wrote:...are your pumps pressure compensated ,so when you slow the flow is doesn't hurt the pump?

Centrifugal pumps don’t really need compensation. They really just provide a pressure boost from inlet to outlet and the flowrate is affected by that lift.

But, if you reduce the flow too slow (through the impeller) with a valve on the suction side, you might see cavitation, which can damage the impeller. In this case, you can regulate the flow from outlet to inlet by plumbing in a bypass loop, which basically runs from the outlet back to the inlet and includes a control valve in the (bypass) circuit.

So, most pond pumps will run fine against a discharge head as long as the suction head is high enough...that is, as long as the pump stays submerged in the reservoir. But flowrate will diminish as the pump discharge “sees” a lift head, or back pressure developed by a piping circuit (flow resistance) or physical elevation lift (refer to Bournouli’s equation).

Now, if using a positive displacement pump, you will need to compensate the discharge pressure if you want to regulate the flowrate. If not, you risk blowing up the seals in your pump. Like the previous example, a bypass circuit will allow you to reduce the output flow without risk to blowing seals....the bypass circuit divides the flow out of the PD pump between your cooling circuit and the bypass loop.
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edit: posted same time as ACfixer.
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Re: Condenser cooling

Postby acfixer69 » Sat Jan 13, 2018 8:24 pm

still_stirrin wrote:
headshaker wrote:...are your pumps pressure compensated ,so when you slow the flow is doesn't hurt the pump?

Centrifugal pumps don’t really need compensation. They really just provide a pressure boost from inlet to outlet and the flowrate is affected by that lift.

But, if you reduce the flow too slow (through the impeller) with a valve on the suction side, you might see cavitation, which can damage the impeller. In this case, you can regulate the flow from outlet to inlet by plumbing in a bypass loop, which basically runs from the outlet back to the inlet and includes a control valve in the (bypass) circuit.

So, most pond pumps will run fine against a discharge head as long as the suction head is high enough...that is, as long as the pump stays submerged in the reservoir. But flowrate will diminish as the pump discharge “sees” a lift head, or back pressure developed by a piping circuit (flow resistance) or physical elevation lift (refer to Bournouli’s equation).

Now, if using a positive displacement pump, you will need to compensate the discharge pressure if you want to regulate the flowrate. If not, you risk blowing up the seals in your pump. Like the previous example, a bypass circuit will allow you to reduce the output flow without risk to blowing seals....the bypass circuit divides the flow out of the PD pump between your cooling circuit and the bypass loop.
ss

edit: posted same time as ACfixer.


is all we were talking about here.

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Re: Condenser cooling

Postby Yummyrum » Sun Jan 14, 2018 12:18 am

My product condenser makes a great bypass :D
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Re: Condenser cooling

Postby headshaker » Tue Jan 16, 2018 4:08 pm

Bypass valve sounds good for the input side d!Two valves in the same tee would be easy to operate .Thanks for all your help guys!Dang yesterday in was 64degrees f,today it 21f .Tomorrow it will start warming to 70 f by the weekend .oh well that's texas.
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Re: Condenser cooling

Postby still_stirrin » Tue Jan 16, 2018 7:12 pm

headshaker wrote:Bypass valve sounds good for the input side d!Two valves in the same tee would be easy to operate.

Well, it would really be better if the control valves were on the discharge side of the condensers. That way, you could be sure that the condensers would always be full of water because they would be at the pump's output pressure rating.

Again, a centrifugal pump has a "dead head" pressure which by definition is the lift (pressure) the pump will put out as the flow goes to zero...i.e. - no flow will circulate. This is the height you could raise the pump's discharge hose above the pump as the flow rate slows and eventually stops.

The other rating of a centrifugal pump is the "no load" or open circuit flow rate, when there is no plumbing on the pump's outlet. Basically, it the maximum flow the pump can put out. The pump "sees" no back pressure from any piping network. Your actual flow rate will be between this (often the GPM/LPH) rating and zero (or dead head).

Knowing this info about your pump, it is always best to keep the piping circuit full of water. So, putting the flow control valves on the discharge side of your condensers (well before the suction side of the pump), you'll be able to regulate the water flow through the individual circuits independently provided that the pump can push enough water through the combined circuits at the discharge pressures needed to establish the desired flow rates.

Stick the pump in a large enough reservoir such that the suction (pump inlet) head is always positive by at least a few inches. That will ensure that the pump won't go into cavitation as you circulate the water. If you need more head lift (to push water to your reflux condenser at the top of your column), you can always raise the whole water reservoir above the floor....except in the case where your reservoir is your swimming pool. Then, you need to have a pump sized with enough discharge flow rate and head lift to pump the water at sufficient flow.

Understand?
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