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Stainless Cross Flow Condenser Idea

These are various style condensers for many different applications.

Stainless Cross Flow Condenser Idea

Postby NineInchNails » Mon Apr 25, 2011 6:51 pm

The overll design is pretty basic, but I had an idea when trying to simplify the construction using stainless sanitary pipe and Tri-Clamp fittings. I know that the drawings below do NOT show a vent, reflux return or anything like that. These drawing are mainly to demonstrate the idea about tooling out the inside of the Tri-Clamp end caps and to get your guys's opinion on it.
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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Mon Apr 25, 2011 6:52 pm

All I would need is 4 Tri-Clamp end caps, 1 long ferrule, 2 gaskets, 2 clamps, some 1/4" tubing and a couple of nipples. I'm sure it would take a good amount of drilling & tig welding, but in the end it should be damn near as simple as it gets. By tooling out the end caps a bit it should eliminate the need for 2 disks with holes drilled into it and the welding of the disks into the main body.

Each gap between the two end caps should be 1/4". Do you guys think that's enough of a gap to NOT restrict the water flow too much?

Here's how I was thinking it could be made:
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Re: Stainless Cross Flow Condenser Idea

Postby Harry » Mon Apr 25, 2011 7:35 pm

That will make the construction relatively simple I would imagine. I haven't worked in S/S so I can't say how much distortion you'd get welding the tubes into the thin end-caps. Others can advise on this. This 'may' impact on the joint sealing correctly after welding.

One thing I am aware of is that triclover clamped joints are notorious for leaking. That's not good for the end-cap water boxes, but it's not such a big issue there. A bigger issue would be the column to condenser triclover. You don't want leaks there.

Be aware also that S/S as condensers have a low heat transfer coefficient compared to copper, and will need to be built larger to compensate for this. But in theory your concept design looks to be a simple way to do it. If you go ahead with it, let us know how it turns out.

Edited for spelling
.


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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Mon Apr 25, 2011 7:55 pm

Harry wrote:That will make the construction relatively simple I would imagine. I haven't worked in S/S so I can't say how much distortion you'd get welding the tubes into the thin end-caps. Others can advise on this. This 'may' impact on the joint sealing correctly after welding.

One thing I am aware of is that triclover clamped joints are notorious for leaking. That's not good for the end-cap water boxes, but it's not such a big issue there. A bigger issue would be the column to condenser triclover. You don't want leaks there.

Be aware also that S/S as condensers have a low heat transfer coefficient compared to copper, and will need to be built larger to compensate for this. But in theory your concept design looks to be a simple way to do it. If you go ahead with it, let us know how it turns out.

Edited for spelling


THANKS for your thoughts Harry!

I have experienced some warp in the past due to the way one guy welded most of my fittings. I brought the majority of my parts to be welded by this guy because he was only charging me $25 per hour. It turned out that while he 'could' tig weld stainless ... he wasn't all that great at it. Most every Tri-Clamp junction did not seat flush with any fitting.

I originally purchased PTFE/Teflon gaskets and they did not seal well due to being so darn rigid. I then ordered Platinum Cured Silicone gaskets and they sealed flawlessly 100% of the time. I have repeatedly filled my 5’ column completely to the top with water and did not get a single leak on any occasion since using these new gaskets. Those gaskets have proved, at least to me, to be absolutely reliable. I have since found a local welder that tigs better than I thought possible. I consider my experience being practically the worst case scenario when it comes to heat warpage. I know that some are concerned about using silicone gaskets in the vapor path, but I’m not all that worried.

Harry I’ve read your book and I noticed that for a 2” column you show using 5.5” long condenser tubes. Would you recommend using longer tubes for a 3” column? If so then I could take your typical recommended tube length and UP that by the approx ratio of thermal resistance that stainless has in comparison to copper. Just a though.
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Re: Stainless Cross Flow Condenser Idea

Postby Harry » Mon Apr 25, 2011 8:23 pm

A 3" column can have a gas/product capability roughly DOUBLE that of a 2" column. On that score alone the reflux condenser (in copper) should be enlarged to compensate. However, the true criteria for a reflux condenser is to handle the amount of power (in kW or BTU's, your choice) that you're pumping in at the boiler end. The design in my paper is in copper, meant for a 2" column powered by 2kW or less.

So the first thing you need to do is decide your power input, then figure the size (heat transfer surface area) of a reflux condenser to handle that, using thermal transfer coefficient for the metal you intend to use. If it's copper, it comes out as one figure (such as my design). If S/S then the figure for surface will be somewhat more. You could do it with complicated math, or just take a WAG & hope it's good enough.
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Re: Stainless Cross Flow Condenser Idea

Postby Chasin' Tales » Mon Apr 25, 2011 8:34 pm

IMO, it would be a lot easier to just use a TC ferrule and end cap for each end. Weld up the shell and tube with some sheet/flat metal on the ends. Then weld the ferrule on top of that. I fear that the end cap would warp bad enough that you would have problems getting a good seal. Stainless steel is bad for that, it would be amplified once you tooled off some of the thickness off the end cap. Not sure if you would also have an issue with flow only having ~1/4 inch space for fluid flow.

I used a section of pipe, some sheet stainless, stainless tubes and a ferrule/end cap for each end of this condenser:
viewtopic.php?f=60&t=3397

I drilled a 1/2" hole in each end cap and welded on a 1/2" NPT coupling. It's an easy build if you have a TIG welder.
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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Tue Apr 26, 2011 10:40 am

Chasin' Tales wrote:IMO, it would be a lot easier to just use a TC ferrule and end cap for each end. Weld up the shell and tube with some sheet/flat metal on the ends. Then weld the ferrule on top of that. I fear that the end cap would warp bad enough that you would have problems getting a good seal. Stainless steel is bad for that, it would be amplified once you tooled off some of the thickness off the end cap. Not sure if you would also have an issue with flow only having ~1/4 inch space for fluid flow.

I used a section of pipe, some sheet stainless, stainless tubes and a ferrule/end cap for each end of this condenser:
viewtopic.php?f=60&t=3397

I drilled a 1/2" hole in each end cap and welded on a 1/2" NPT coupling. It's an easy build if you have a TIG welder.


I checked out your thread and I think you're right. Doing it that way would be very safe and less chance of warping the ferrules. So how is that condenser working for ya? I’d really like to know. I assume you’re running electric elements. I’m on propane burners at the moment.

The guy who tigs for me now does an amazing job (though at approx $60/hour). I can barely see the welds. It's like he just sews the pieces together. The fittings he has welded for me lately show no signs of warping at all and I was surprised considering they were ss threaded couplings. I have a good feeling that he could do this without harming anything and I’m sure he would tell me if he couldn’t.

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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Tue Apr 26, 2011 10:53 am

Harry wrote:A 3" column can have a gas/product capability roughly DOUBLE that of a 2" column. On that score alone the reflux condenser (in copper) should be enlarged to compensate. However, the true criteria for a reflux condenser is to handle the amount of power (in kW or BTU's, your choice) that you're pumping in at the boiler end. The design in my paper is in copper, meant for a 2" column powered by 2kW or less.

So the first thing you need to do is decide your power input, then figure the size (heat transfer surface area) of a reflux condenser to handle that, using thermal transfer coefficient for the metal you intend to use. If it's copper, it comes out as one figure (such as my design). If S/S then the figure for surface will be somewhat more. You could do it with complicated math, or just take a WAG & hope it's good enough.


I'm running a big ol propane burner and it might make my head spin trying to estimate out how much power is being put inside the boiler. I imagine I'd have to know what the temp is of the water I start out with, fire up the burner, set it at the desired setting, begin timing it, periodically note the temp and calculate the kW/BTU energy put inside the boiler or something like that.
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Re: Stainless Cross Flow Condenser Idea

Postby Chasin' Tales » Tue Apr 26, 2011 11:28 am

[quote="NineInchNailsI checked out your thread and I think you're right. Doing it that way would be very safe and less chance of warping the ferrules. So how is that condenser working for ya? I’d really like to know. I assume you’re running electric elements. I’m on propane burners at the moment.

[/quote]

It works like a champ. I added the extra takeoff about halfway up the horizontal section of the condenser just to see if any vapor was being knocked down that far up. I've kept that valve open and so far not a drop has come out. That is with the cooling water turned down to a slow trickle. That was with a 2000W element at full power. I used 21 1/4" tubes inside of a 1 foot section 3" pipe.

Cost wise, using a ferrule and end cap should be just about the same as two end caps and will be easier to do in the long run.

That's the nice part about TIG...provided there's not much gap you can often just fuse the two pieces together with no filler metal. Doing it like that also throws less heat a the piece making it less likely to warp.

Best of luck!
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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Tue Apr 26, 2011 12:21 pm

Well just for fun I've been playing with the Condenser Size Calculator. I've been trying to see if that calculator relates well with Harry's design.

I've been leaving most of the fields with their default values
I entered 6.35mm (1/4") for tube diameter because Harry used 1/4" copper tubes in his design.
I entered 2000W for heat input based on Harry's statement, "The design in my paper is in copper, meant for a 2" column powered by 2kW or less".

When I hit 'Calculate' I get the following values:
Typical length needed: 2.49m (98")
Typical water flow rate needed: 0.82 l/m (0.22 g/m) Sounds like a slow & steady trickle

When I divide 98" by 19 (the number of 1/4" tubes in Harry's cross-flow design) I get = 5.16" and the plans call for 19 6" tubes.
That tells me that that this calculator jives with Harry's design and/or vice versa. VERY :8)

If I knew approx what the Heat Transfer Coefficient of a given size of ss tube I wanted to use then this calculator could be of some serious help. I have found some info, for instance here, but it will take a while before it sinks in and make some sense of it.

I realize that this is all revolves around knowing the heat input and at the moment I do not have the foggiest clue what mine would be.
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Re: Stainless Cross Flow Condenser Idea

Postby Harry » Tue Apr 26, 2011 1:56 pm

Hi NIN,

I did warn you that the math was conplicated. Now that you have discovered for yourself that my crossflow design is within specs, :D

use my condenser as the baseline for 2kW, and increase those dimensions by percentage to allow for your power input. You'll need to allow extra for the S/S poor heat conduction. How much extra is that? I dunno. But refer to Chasin' Tales sizing & usage as a guide.

The difference between S/S and Copper as heat conductors (lookup below) is a significant difference and the reason I don't use S/S for heat transfer duties. But as has been shown, S/S can be used, just you need to make allowance (make it bigger) for the heat transfer capability of S/S compared to copper.

A S/S column (for slower heat loss) and a Copper Crossflow (for fast heat transfer) is an ideal combination for reflux stills.





thermal-conductivity-chart-for-metals.png
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Re: Stainless Cross Flow Condenser Idea

Postby minime » Tue Apr 26, 2011 2:03 pm

NIN, your plumbing should show the hot water exit at the top of the condenser or you're only gonna fill the bottom half of the the condenser with water.
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Re: Stainless Cross Flow Condenser Idea

Postby Harry » Tue Apr 26, 2011 2:25 pm

minime wrote:NIN, your plumbing should show the hot water exit at the top of the condenser or you're only gonna fill the bottom half of the the condenser with water.


Yes I made allowance for that in my design. However in practice it will depend very much on the water flowrate. Fast it don't matter, slow it will matter, because you'll get just what you mention, Mini.
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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Tue Apr 26, 2011 2:36 pm

minime wrote:NIN, your plumbing should show the hot water exit at the top of the condenser or you're only gonna fill the bottom half of the the condenser with water.


Harry wrote:
minime wrote:NIN, your plumbing should show the hot water exit at the top of the condenser or you're only gonna fill the bottom half of the the condenser with water.


Yes I made allowance for that in my design. However in practice it will depend very much on the water flowrate. Fast it don't matter, slow it will matter, because you'll get just what you mention, Mini.


:doh: Thanks guys. I never considered that. I remember seeing that incorporated in people's pics. I wondered what that that little standpipe inside the end caps were for, but it never occured to me :lol: Easy fix, thanks again guys.

Good thing were not building bombs :o
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Re: Stainless Cross Flow Condenser Idea

Postby NineInchNails » Tue Apr 26, 2011 2:38 pm

Harry wrote:Hi NIN,

I did warn you that the math was conplicated. Now that you have discovered for yourself that my crossflow design is within specs, :D

use my condenser as the baseline for 2kW, and increase those dimensions by percentage to allow for your power input. You'll need to allow extra for the S/S poor heat conduction. How much extra is that? I dunno. But refer to Chasin' Tales sizing & usage as a guide.

The difference between S/S and Copper as heat conductors (lookup below) is a significant difference and the reason I don't use S/S for heat transfer duties. But as has been shown, S/S can be used, just you need to make allowance (make it bigger) for the heat transfer capability of S/S compared to copper.

A S/S column (for slower heat loss) and a Copper Crossflow (for fast heat transfer) is an ideal combination for reflux stills.





thermal-conductivity-chart-for-metals.png

Thanks a million for that chart Harry! I saved that one for future reference. I knew that stainless was less conductive, but I never thought it was that less. I’ll play with some numbers and see what I come up with.

Making a condenser out of copper is not completely out of the question that's for sure. I just love stainless though.
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