plumbing condensers in series vs parallel

[Benredbeard]

I think I have a data point stuck in my head that needs to be deleted but please confirm: it is coolant management in which it's beneficial to split the coolant flow (PC and RC) and control individually right?

In a CCVM just go reservoir > PC > RC > reservoir right? With a cold finger style RC is it important which side to have as the inlet (finger flows down then coil back up for example)?

[ShineonCrazyDiamond]

Correct. In my experience, anyway.

CCVM, all you need to do is get it cold enough to knock down all the vapor. That is the only requirement. With my CM, it comes down to the very hair of adjustment, until it's set. Then no worries.

Could you benefit from split controls in a CCVM? Maybe. Maybe not enough to facilitate need, imo. Just run the PC a little colder. At best, maybe save a little water.

Can you run a CM, i.e., a flute, with one control. It's possible, I guess. But it would add so much headache, I would never do it. With you needing to be able zero in on both heat and cooling flow.... I'd be so frustrated I'd kick it over. But that's me. There might be some here that can get the flow the want with loaded plates while using 1 water valve. To me, it's worth it to split it.

[LWTCS]

Can run the RC off of the PC discharge if your PC is large enough to not compromise the operating range of your RC.
The smaller PCs would otherwise lock you into very limited production speeds if you are looking to run a higher reflux ratio.

As mentioned, its best to plumb with independent control. Also don't forget to install your flow control valves on the discharge side on either of your HXs.

[OtisT]

With a cold finger style RC is it important which side to have as the inlet (finger flows down then coil back up for example)?

My understanding of this is that the top of the coil in a RC should be the inlet (coldest), so that the coil is progressively hotter the lower you go. You want the coldest part of the coil at top, and the hottest side on the bottom. That way your liquid RC drops as warm as possible.

Otis

[kimbodious]

I run my condensers on my CCVM in series using recirculated water. As long as you have enough cooling to put your columnin to total reflux, when you want, you are good to go.

[shadylane]

Just a thought
I figure a CCVM would be sencitive to cooling water temp variations.

[ShineonCrazyDiamond]

Just a thought
I figure a CCVM would be sencitive to cooling water temp variations.

No, that's the beauty. Whether it's 50 degrees or 5.... does it knock 100% down the column that reaches it? Cooling has nothing to do with how much goes to the output. The reflux condensor is just a valve. It either hits the condenser, or it doesn't. Doesn't matter how cold the reflux is as long as it's enough to collapse it.

[shadylane]

Based on my limited experiments with CCVM, I'll have to disagree.
Picture a CCVM at mid run. Raise the input cooling water temp and see what happens.
The reflux ratio, and ABV will decrease.

[kimbodious]

Based on my limited experiments with CCVM, I'll have to disagree.
Picture a CCVM at mid run. Raise the input cooling water temp and see what happens.
The reflux ratio, and ABV will decrease.

What amount of water temp variation are you picturing? Your scenario would work on a CM but not on a CCVM unless the cooling water becomes boiling hot

In my scenario the bottom of the RC is well above the top of the offtake. As long as that RC is cool enough to condense the vapour then all things being equal (diameters of column vs offtake) 50% of the vapour is exiting via the offtake.

Think of the RC as a moveable bung of coldness, no vapour escapes as long as the bung is cool enough to condense the vapour. If the bung gets too warm then vapour gets lost to the atmosphere and of course reflux ratio and ABV will decrease

[shadylane]

I've played around with controlling a CM dephleg using preheated water.
It's very effective, but added another variable into the balancing act.
Using the same preheated water on CCVM also changed how it worked. Although not as much as the CM.
The direction of cooling water flow and if the CCVM was vented or not also had an effect.

[kimbodious]

Sorry, I still don’t get it? If the cold zone becomes a tepid zone the vapour just travels higher up the RC but it still condenses -just higher up.

If you’re not losing vapour, you have enough HETP in the column and getting reflux without flooding then I can’t see how the temperature of the RC cooling water has an impact on ABV?

I am not saying you are wrong Shady, I just can’t get my head around what is causing the changes you observed.

[shadylane]

The cooling zone isn't a uniform tepid or cold.
But varies depending on amount of energy each coil is absorbing.
Try lowering the CCVM down to the point were it's partially blocking the outlet.
Then change the cooling water temp and see what happens

[kimbodious]

Okay, I can understand that if someone has a column which is less than ideal, does not have enough HETP equivalents and has to run their column with the RC in a lower position to maximise purity.

Over the years I have tuned my column so that now I can fully raise the RC and pull 95-96% all day long (it feels like that sometimes). I use 3 settings for my RC. Right down for total reflux, Up 1/2” for drawing off foreshots and heads and up 4” for the remainder of the run. My RC spends the vast majority of the time fully raised, that is why I was having difficulty understanding the process you were describing

[shadylane]

I think I have a data point stuck in my head that needs to be deleted but please confirm: it is coolant management in which it's beneficial to split the coolant flow (PC and RC) and control individually right?

Yes you definitely need to run a CM with the cooling water in parallel
On a CCVM I'd still recommend parallel flow

In a CCVM just go reservoir > PC > RC > reservoir right?

For series flow, I'd go reservoir - RC - PC - reservoir
This way, the RC will have a more consistent water temp

With a cold finger style RC is it important which side to have as the inlet (finger flows down then coil back up for example)?

I'm not sure which is best

[kimbodious]

from reservoir - PC - RC - back to reservoir if in series

[shadylane]

With a cold finger style RC is it important which side to have as the inlet (finger flows down then coil back up for example)?

My understanding of this is that the top of the coil in a RC should be the inlet (coldest), so that the coil is progressively hotter the lower you go. You want the coldest part of the coil at top, and the hottest side on the bottom. That way your liquid RC drops as warm as possible.

Otis

Sounds logical to me