CSST condenser performance trouble

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ckdistills
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CSST condenser performance trouble

Post by ckdistills »

I'm having knockdown trouble with my ~60" 5/8 OD CSST "twisted U" product condenser in a 2" CCVM in pot still mode. At 1.5kw, vapor is being knocked down but the distillate is quite hot (110 F) and there is barely a temperature gradient on the outside of the spool where the PC is. At 2 kw, distillate is hotter and there is condensation on the CCST near where it exits the spool so vapor is either escaping or very close to escaping and I turn it down. This has been an issue the last 4 stripping runs - the still wasn't used for a number of months prior. I took it apart between the 2nd and 3rd runs to visually inspect and nothing seems to be out of the ordinary.

I'm recirculating cooling water and it's been sufficient on a dozen or so earlier runs. The starting temp of the water was likely cooler due to seasonal changes but I didn't take notes related to the temperature of distillate or cooling water. I recall cool distillate that warmed up in the last third or so of the run.

On my last run, cooling water started at 64 F and ended at 84 F. The last measurement of distillate temp was 110 F when the cooling water was 78 F. The cooling water output is warmer but not substantially warmer than the water in the recirculating container. A pond pump is running full bore, I haven't measured gallons/minute but it is way higher with far less performance than the 1 liter/minute described here:
A 20" keg spear with 1/2" coolant line Dimroth, can handle 4,500 watts. Water supply needs to be less than 80 deg F at one liter a minute.

Any ideas about how I can increase performance or what might be incorrect with my setup? I'd like to be stripping at 2.5 - 3.5 kw instead of 1.5!
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Re: CSST condenser performance trouble

Post by jonnys_spirit »

Cool! I guess you’re using the csst in a dimroth PC configuration.

First thought is if it worked before and is wound the same way - try swapping input and output feeds to the coil?

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Re: CSST condenser performance trouble

Post by Demy »

Could the cooling water temperature have changed?
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Re: CSST condenser performance trouble

Post by kimbodious »

how big is the water reservoir that the pump is in?
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Re: CSST condenser performance trouble

Post by Bee »

Any kinks in the CSST?
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Re: CSST condenser performance trouble

Post by ckdistills »

Thank you all.

Jonny:
Yes - Dimroth type PC configuration. I can try swapping input/output but it's twisted not coiled so not sure how this would make a difference?

Demy:
Yes, the cooling water is warmer due to seasonal changes. I didn't take notes on cooling temp on earlier runs but I'd guess 10 degrees warmer starting temp? Last run it ended at 84 degrees - doesn't seem too hot.

Kimbodious:
32 gallon reservoir. I know that's on the smaller side but in last run water temp ended at 84ish degrees - I'm doing 5 gallons charges in my 7.5 gallon still.

BTW, your posts & design have been inspiration for mine!

Bee:
I just took it fully apart to verify. No kinks.


Here is a picture of the mostly dissembled PC. Copper mesh interwoven (that I need to clean!). It's about 13" of condenser coil before the T where it exits.
IMG_0509.jpeg
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Re: CSST condenser performance trouble

Post by jonnys_spirit »

ckdistills wrote: Wed Jun 07, 2023 11:34 am Jonny:
Yes - Dimroth type PC configuration. I can try swapping input/output but it's twisted not coiled so not sure how this would make a difference?
Just a thought. Did something block it partially maybe? Everything else equal not sure why it may be different now but possible flow restriction, pump issue, or cooling water temp are what jumps up on my list..

Cheers,
j
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Re: CSST condenser performance trouble

Post by ckdistills »

jonnys_spirit wrote: Wed Jun 07, 2023 11:39 am
Just a thought. Did something block it partially maybe? Everything else equal not sure why it may be different now but possible flow restriction, pump issue, or cooling water temp are what jumps up on my list..

Cheers,
j
Yea I'm going to hook it up to garden hose and blast it with full water pressure.
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Re: CSST condenser performance trouble

Post by kimbodious »

I tried using a pond pump in a 200 litre drum for a reticulating water supply and even with an evaporative cooling set up it got too warm. The pond pump also generates heat.
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Re: CSST condenser performance trouble

Post by zach »

I found this topic kind of interesting so I did some calculations to see if the original performance claim seems reasonable and to figure out why the OP is having difficulty.

Below is the summary of the calculations.
Energy Balace.jpg
The heat transfer rate ("U") from the condenser performance from ckdstills is 6 times lower than the DAD300.

I think the issue is likely on the vapor side rather than the cooling water.

Non condensable gas (air) can cause dramatic reductions of heat transfer in a condenser. In refrigeration and steam rankine cycles, air purging of the system is critical for condensers to operate a peak efficiency. Air can act like a blanket effectively reducing heat transfer area.

I've seen a distillation systems that have a "vent condenser" like the diagram below which allows air to be pushed out of the main condenser during start up of a continuous cycle.
flow diagram.jpg

The vapor pathway in the DAD300 condenser is more restrictive which at higher mass flow rates creates enough velocity to carry the air out the bottom of the condenser thus better heat transfer.

As for ways to correct,

1) Try adding the cheese cloth as DAD300 does in his post to the condenser outlet and the tee to see if the restriction helps reduce the air in the condenser.

2) Consider getting a smaller diameter outer tube like the keg spear if your tubing fits inside.
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Re: CSST condenser performance trouble

Post by shadylane »

ckdistills wrote: Tue Jun 06, 2023 7:49 pm

Any ideas about how I can increase performance or what might be incorrect with my setup? I'd like to be stripping at 2.5 - 3.5 kw instead of 1.5!
Try removing the copper mesh.
Have you got a pic of the condenser connected to the rig?
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Re: CSST condenser performance trouble

Post by ckdistills »

zach wrote: Thu Jun 08, 2023 10:33 am
As for ways to correct,

1) Try adding the cheese cloth as DAD300 does in his post to the condenser outlet and the tee to see if the restriction helps reduce the air in the condenser.

2) Consider getting a smaller diameter outer tube like the keg spear if your tubing fits inside.
Wow - interesting! Thank you for running those numbers! I thought about a narrower diameter tube and discounted it as I thought increasing vapor speed would result in a less efficient condenser due to shorter contact time. I'm going to try reducing air in the condenser first.
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Re: CSST condenser performance trouble

Post by ckdistills »

shadylane wrote: Thu Jun 08, 2023 3:57 pm Try removing the copper mesh.
Have you got a pic of the condenser connected to the rig?
That's interesting Shady. Will try removing the mesh as well - that is actually a difference between previous stripping runs and these ones. I added the mesh during my last spirit run after stripping.

Picture of rig as well. It's sitting on a 7.75 gallon 1/4 keg with a 3500 watt element.
IMG_0511.jpeg
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Re: CSST condenser performance trouble

Post by shadylane »

ckdistills wrote: Tue Jun 06, 2023 7:49 pm At 1.5kw, vapor is being knocked down but the distillate is quite hot (110 F) and there is barely a temperature gradient on the outside of the spool where the PC is.
Nice rig. :thumbup:

A Dimroth condenser doesn't have a temp gradient like a liebig does.
There isn't any cooling water flowing through the jacket.
The distillate will also be hotter, because the lower half of a liebig acts like a chiller.
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Re: CSST condenser performance trouble

Post by ckdistills »

More data points! Just finished first of 3 (or 3.5 stripping runs) with a new ferment. Here's the plan.

1st run: remove the mesh (done - data below)
2nd run: replace hose connection on condenser (see why below)
3rd run: add cheesecloth to tee & condenser output to restrict/reduce air in the condenser


5 gallon charge. The condenser input hose is slightly collapsed from overheating it - it's visible in the picture above. There is still a great flow rate from the pump so I didn't realize the difference it would make. From the data below, pinching it as open as possible results in a 10 degree temp difference in the distillate!

The distillate temperature increased more slowly than the cooling water temp. There was a 34 degree delta between the cooling input and the distillate at the beginning and a 15 degree difference at the end. There was also a consistent 6-7 degree difference between the cooling water input (reservoir) and the output across the run.

10:30 AM
first drips
cooling water reservoir 66 degrees (F)
11:00 AM
2 kw
cooling water reservoir 70 degrees
condenser output 77 degrees
distillate 115 degrees (input hose slightly collapsed)
distillate 104 degrees (input hose held open)
11:15 AM
2.5 kw
distillate 120 degrees
distillate 110 degrees (holding hose open)
reservoir 77 degrees
output 85 degrees
11:30 AM
distillate 117 degrees
reservoir 86 degrees
output 92 degrees
12:00 PM
distillate 112 degrees (open)
reservoir 97
output 104
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Re: CSST condenser performance trouble

Post by ckdistills »

Cut down the hose connectors tonight so they won't collapse.
IMG_0566.jpeg
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Re: CSST condenser performance trouble

Post by Wildcats »

ckdistills wrote: Mon Jun 26, 2023 12:38 pm More data points! Just finished first of 3 (or 3.5 stripping runs) with a new ferment. Here's the plan.

1st run: remove the mesh (done - data below)
2nd run: replace hose connection on condenser (see why below)
3rd run: add cheesecloth to tee & condenser output to restrict/reduce air in the condenser


5 gallon charge. The condenser input hose is slightly collapsed from overheating it - it's visible in the picture above. There is still a great flow rate from the pump so I didn't realize the difference it would make. From the data below, pinching it as open as possible results in a 10 degree temp difference in the distillate!

The distillate temperature increased more slowly than the cooling water temp. There was a 34 degree delta between the cooling input and the distillate at the beginning and a 15 degree difference at the end. There was also a consistent 6-7 degree difference between the cooling water input (reservoir) and the output across the run.

10:30 AM
first drips
cooling water reservoir 66 degrees (F)
11:00 AM
2 kw
cooling water reservoir 70 degrees
condenser output 77 degrees
distillate 115 degrees (input hose slightly collapsed)
distillate 104 degrees (input hose held open)
11:15 AM
2.5 kw
distillate 120 degrees
distillate 110 degrees (holding hose open)
reservoir 77 degrees
output 85 degrees
11:30 AM
distillate 117 degrees
reservoir 86 degrees
output 92 degrees
12:00 PM
distillate 112 degrees (open)
reservoir 97
output 104
I would want my distillate cooler then that. But that's just me. As long as you like the taste of what you're making then that's all that matters. Have fun and stay safe.
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Re: CSST condenser performance trouble

Post by ckdistills »

Wildcats wrote: Tue Jun 27, 2023 2:53 am I would want my distillate cooler then that. But that's just me. As long as you like the taste of what you're making then that's all that matters. Have fun and stay safe.
Agreed, any suggestions on getting better performance from my condenser? I'm surprised that removing the mesh improved performance and am curious to see how the other suggestions in thread perform.

From this last run, it seems that cooling water velocity has a larger impact than water temperature. I'm running a 400 GPH aquarium pump full out. Next run I'll measure its actual throughput in my setup.
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Re: CSST condenser performance trouble

Post by Wildcats »

ckdistills wrote: Tue Jun 27, 2023 7:51 am
Wildcats wrote: Tue Jun 27, 2023 2:53 am I would want my distillate cooler then that. But that's just me. As long as you like the taste of what you're making then that's all that matters. Have fun and stay safe.
Agreed, any suggestions on getting better performance from my condenser? I'm surprised that removing the mesh improved performance and am curious to see how the other suggestions in thread perform.

From this last run, it seems that cooling water velocity has a larger impact than water temperature. I'm running a 400 GPH aquarium pump full out. Next run I'll measure its actual throughput in my setup.
Wish I had a good answer for you. I have a shotgun condenser and have never run one like you have. So I can't really help ya there. But I can tell you that if you're thinking of building a shot gun then Twisted Brick makes and sells end caps and baffles that make the build a piece of cake. Either way I hope you get it sorted out man.
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Re: CSST condenser performance trouble

Post by BoilerMaker »

Perhaps air is in the CSST at low flow rates? If CSST is large diameter and flow rate is a trickle, would it not fill the inlet/"up" side, then trickle over the top and leave the "down" side partly full of air. Depending I guess if the lines and reservoir are positioned below the CSST and flow control valve is on the inlet side. Moving the valve to the outlet side and burping the air out before connecting the PC to lyne arm might help.
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Re: CSST condenser performance trouble

Post by elbono »

I have a similar condenser it's CSST in copper pipe. The CSST is 3/8 nominal, measures 1/2 OD the copper is 1 type M, actual ID is 1.055. For the CSST to fit I have to run a untwisted U. The CSST is 72" but from the U bend to where it comes out of the pipe is 30". I put small pieces of SS wool at the entrance and exit. I choke the input water and keep the output hot to conserve city water usage.

Anyway, today I did a stripping run. I set the power to 2500 watts to match your data. The city water was coming in at 75F and the outflow was 120F, this was about 1/2 liter/min flow. Distillate was 90F. Your temps and flow should give you lower distillate temp.

I don't worry about distillate temp on stripping runs normally and run hotter water out and distillate than this. I can feel a temp gradient and adjust so the condenser is warm but not hot at the output end.

I think you should get better results than your data shows.

How are you measuring power?
I use a true TMS multimeter to measure element voltage and convert to watts. I'm using a phase control SSR (module + pot type), a lot of ways to measure power will be wildly inaccurate on these. You may be running a lot more power than you think. Use the time to temp calculator to confirm your measurements.
https://homedistiller.org/wiki/htm/calc ... d14701.htm
It's only so good but should pick up gross inaccuracies.

There is definitely air in the the downhill side of the CSST, even if you manage to start with no air pockets the water contains dissolved air it will release when heated. Unless the flow creates enough turbulence to carry it out you get an air pocket.
Can you make a coil around a straight section (this is what a Dimroth really is) and still fit it in the shell? If you put water in the coiled side more of the CSST will be filled with water.

It seems you're getting poor heat transfer between the water and distillate, try putting your scrubbies in various places.
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Re: CSST condenser performance trouble

Post by shadylane »

elbono wrote: Thu Jun 29, 2023 1:47 pm
It seems you're getting poor heat transfer between the water and distillate, try putting your scrubbies in various places.
If you're looking for max performance.
The best place to put scrubbies is in the drawer. :lol:
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Re: CSST condenser performance trouble

Post by shadylane »

ckdistills wrote: Tue Jun 27, 2023 7:51 am
From this last run, it seems that cooling water velocity has a larger impact than water temperature. I'm running a 400 GPH aquarium pump full out. Next run I'll measure its actual throughput in my setup.
Plus one on flow.
It seems to me, a dimroth needs more water than a liebig to knock down the same.
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Re: CSST condenser performance trouble

Post by kimbodious »

shadylane wrote: Thu Jun 29, 2023 5:52 pm
elbono wrote: Thu Jun 29, 2023 1:47 pm
It seems you're getting poor heat transfer between the water and distillate, try putting your scrubbies in various places.
If you're looking for max performance.
The best place to put scrubbies is in the drawer. :lol:
My experience does not support your statement. The scrubbers serve an important purpose to reduce any gap between the walls of the chamber and the coil. It is not always possible to ensure that the coil is a close fit in the chamber leaving significant gaps. My CSST coil for the CCVM RC has the scrubber part way up and you can certainly feel on the outside of the RC a cold zone where the section with the scrubber is.
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Re: CSST condenser performance trouble

Post by shadylane »

Sounds like you need to center the CSST tubing instead of adding scrubbies.
The cold spot is due to hot vapor not getting to that area.

Scrubbies get in the way of vapor and cause it to speed up.
Have you ever seen scrubbies being used on any commercial condensers?
I haven't
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Re: CSST condenser performance trouble

Post by kimbodious »

shadylane wrote: Fri Jun 30, 2023 6:10 pm Sounds like you need to center the CSST tubing instead of adding scrubbies.
The cold spot is due to hot vapor not getting to that area.

Scrubbies get in the way of vapor and cause it to speed up.
Have you ever seen scrubbies being used on any commercial condensers?
I haven't
The cold spot is where the vapour is condensing. Below is hot, above is cold. If the vapour gets past the RC in a CCVM, the next stop is the atmosphere, In a CCVM the RC chamber is above the offtake.
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Re: CSST condenser performance trouble

Post by shadylane »

kimbodious wrote: Fri Jun 30, 2023 8:20 pm
Err the cold spot is where the vapour is condensing. Below is hot, above is cold. If the vapour gets past the RC in a CCVM, the next stop is the atmosphere! In a CCVM the RC chamber is above the offtake.
Here's part of the confusion. :lol:
The OP, ckdistills was asking about a Dimroth product condenser.
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Re: CSST condenser performance trouble

Post by kimbodious »

shadylane wrote: Fri Jun 30, 2023 8:43 pm
kimbodious wrote: Fri Jun 30, 2023 8:20 pm
Err the cold spot is where the vapour is condensing. Below is hot, above is cold. If the vapour gets past the RC in a CCVM, the next stop is the atmosphere! In a CCVM the RC chamber is above the offtake.
Here's part of the confusion. :lol:
The OP, ckdistills was asking about a Dimroth product condenser.
Oops my mistake! I am happy to stand corrected. Thanks. Hopefully the OP has fixed their issue with the hoses and fittings that can stand higher temperatures without deforming. TBH I don’t think the reservoir is large enough to stay cool enough for a long spirit run.
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Re: CSST condenser performance trouble

Post by shadylane »

kimbodious wrote: Fri Jun 30, 2023 8:51 pm
Hopefully the OP has fixed their issue with the hoses and fittings that can stand higher temperatures without deforming. TBH I don’t think the reservoir is large enough to stay cool enough for a long spirit run.
Hoses and fittings need to be done right. :thumbup:
What works on the cold side might not be good enough on the hot.
Hoses tend to sag down when hot.
I prefer to have the hose connect pointing straight down.
So there's no possibility of the hose kinking.
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Re: CSST condenser performance trouble

Post by kimbodious »

shadylane wrote: Fri Jun 30, 2023 9:03 pm
kimbodious wrote: Fri Jun 30, 2023 8:51 pm
Hopefully the OP has fixed their issue with the hoses and fittings that can stand higher temperatures without deforming. TBH I don’t think the reservoir is large enough to stay cool enough for a long spirit run.
Hoses and fittings need to be done right. :thumbup:
What works on the cold side might not be good enough on the hot.
Hoses tend to sag down when hot.
I prefer to have the hose connect pointing straight down.
So there's no possibility of the hose kinking.
True. I have learned that the hard way and it escalates. A slight blockage leads to deformation hotter conditions leading to greater blockage and catastrophic conditions! I have gone to 3/4” triclamp fittings and hoses and don’t connect to garden hose type fittings until I have taken the hoses down to the ground. Water leaks were the bane of my hobby until I went to TC fittings. I have been using a recirculating water system over long runs hence the 3/4” hoses.
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