Purchased tank to make into vacuum kiln

[Den Socling]

Craig,

Those cooling towers on ebay are the same as I use. I think there are two or three distribution points for these towers in the US. Somebody is buying and reselling on ebay. They are cheap, last forever and work well when kept clean. http://www.mesanct.com/html/eng/company/index.htm

Today, my little tower was running 60 +/-5'F.

Den

[Den Socling]

I just checked the prices for those towers. You would need only the smallest and the 'buy it now' price is about the same as mine so it looks like a decent deal.

[boardwalker]

Den

Do I need to set the cool tower up with a temperature control or can it run as long as the vacuum pump is running?

[Den Socling]

You could leave it run but I would add temperature control. We store our cooling water in an in-ground tank. The temperature control pumps water to the tower as needed. It also kicks on the fan when needed. With this set up, you don't worry about freezing. But it is kind of elaborate.

[boardwalker]

Den

Will a single pass shell and tube heat exchanger work as a condenser, and does the inlet and outlet have to be 1 1/4" or larger or can it be 1"?

[Den Socling]

Single pass S&T is what you want. 1" will do. Put water on the shell side. Stand vertically. Connect the top to the vac pump. Put a tee in the bottom of the tube side. below the tube. connect a PVC condensate collection tank or drain it back into the kiln and then dump water from the kiln floor during the vac-off side of the cycle.

[boardwalker]

Den

Are the side ports the shell and the top and bottom ports the tubes?

[Den Socling]

yep

[boardwalker]

Den

I know we talked about the need for a ball check valve on the vacuum pump and we decided that it did not need on since it was a dis-continuous system, but I was rethinking this and wandered if the vacuum in the tank would suck back through the pump when it was shut off with out the check valve?

[serg]

Craig, hi!
I observed of this string. The engineering of drying vacuum faltering will not give good result. I have many drawings on vacuum to a faltering method of drying. I have left from this way.
You should know that humidity in one tree trunk different. You warm up up to temperature 70 C do(make) vacuum 0.8 ìïà, temperature of boiling 58 C at presence of free water in a tree internal cracks will appear. If to supervise temperature of a tree. Then it is necessary to put the gauge in each board of a stack, drying to carry out(spend) on the highest humidity of a tree! If you do not warm the case you " will work to Alaska as has told Den ", the big losses of heat.
The fan will give a problem not equal warming up of a stack, dead zones, the tree will dry not in regular intervals.
The case collects pairs in a condensate, you receive superficial cracks, end faces of boards will burst. You should establish in addition humidifying of a tree.
From 70 % of humidity up to 30 % of humidity of a tree the boiling point is forbidden! Remember free water of a tree well leaves without vacuum. The vacuum does(makes) responsible(crucial) drying from 30 % up to 6 %. When a board warm in regular intervals on all section, humidity of 30 % then it is possible to finish boiling, heavy water in walls of a cell(cage) begins to boil in regular intervals leaves on a surface, humidifies the top layer of a board that gives quality.
Pairs should be constantly in the case of the chamber.
Remember many(a lot of,much) pair poorly, the pair poorly is not enough!
For your cylinder vacuum enough pump the membrane of type, works without oil, without water.
To dry an oak from humidity of 70 % up to 6 % for 14 days, my conclusions are not present. Quality will turn out for 28 days.
For evaporation of 1 litre of a moisture it is required to you 1.2 kw.
For drying a board of 1 m3 is required to you 3 kw heat. For your tank it is possible to establish the boiler 12 kw.
I have applied not faltering vacuum and faltering is warm. The top layer cools down and pulls a moisture from middle of a board on a surface, warmly evaporates and deduces for the chamber a moisture with the help a condensate of the collection pair. A part pair constantly in the chamber.
If you will do(make) faltering vacuum it is possible to establish the return valve on the vacuum pump, the big inlet valve.
This my opinion.
Sergey.

[Den Socling]

Craig,

Yes you need the ball-check or, as you say, the chamber will pull water from the pump.

Sergey,

The goal is a vacuum kiln that people without a lot of money can build. Discontinuous vacuum is not my favorite technology but I have seen it dry 75mm red oak squares. The system I saw ran on timers and had been running for (I'm guessing) more than 20 years. The company that had it did scrap it and converted to our technology which is much faster and easier and generally better but much more expensive!

I don't like running a kiln charge from one sample. I suggested in the beginning that multiple sensors might be put in the charge and then one could be chosen for control.

I warned in the beginning that even air flow through the kiln charge would be difficult to achieve. I like your system with natural convection but I believe that your system should have pressure control and that adds cost.

I don't see this system working as a production kiln but as a hobby kiln that might do well enough to supply a hobbyist and possibly have a surplus for sale.

Den

[serg]

Den, it is the powerful answer of the professional! That you me understand thank.
Let's specify.
The oak dries 75 mm from what humidity and up to what?
All manufacturers of drying chambers of Russia, never write as dries a wood a dryer on thickness of 75 mm an oak?
They never write what residual pressure(voltage) in a board?
Den in America there is a quality, requirements of quality?
Russia: 1 category of quality 8 +/-2 %
                 2 category of quality 12 +/-2 %
                  3 category of quality 18 - 22 %
I criticize system of quality in Russia. Steady humidity in regions 6 +/-2 % whereas it can turn out 8 + 2 % = 10 %? 
The science of Russia is silent!
In America quality of drying such estimation? Russian study from America. :P
To build such vacuum dryer Craig cheaply will fail. Cheaply it is possible to buy technology and to make with the warranty of drying, to carry out(spend) experiment on needy I did not begin to do(make) and give it advice(councils)? I have told, I have given a guarantee that she(it) very problematic.
It will be possible to tell that she(it) to dry, I with it shall agree.
Quality of 8-14 % on length of a board, 4 % difference on thickness of a board, internal cracks are inevitable. Then it is possible to continue to build this vacuum furnace.
Craig should do(make) the tested variant.
Den problems of system of work of faltering vacuum will be problems. What will do(make) Craig?
You can do(make) to it(him) the help with a guarantee of the technology? Then money will be rescued.
Sergey.

[Den Socling]

Sergey,

Red oak around here averages 70% moisture content off the saw. Final moisture content for 75mm squares is 6 to 8%. They are often used as newels (post) in stair cases.

I have an idea. Suppose we help Craig build a kiln that can function both like your natural convection, steam vac or a discontinuous vac with fans for circulation. Both methods require a stickered load. He would need the heating tubes in the bottom and the condenser in the top of the cylinder. He could try heating at 760" Hg or 200" Hg.

Always dreaming.
Den

[boardwalker]

Den & Sergey

I'm willing to give this a try if Sergey is willing to give me the information to make it work, and if you both work together to pound all this information into my thick head so that I can understand what I'm doing.

I like the idea of using the fans for the circulation because with the small chamber that I have having to leave a gap for natural circulation would not let me dry anything wide.

How many feet of pipe would I need and what size should it be? How many cubic feet per minute of air circulation should there be?

[serg]

Den, I could not understand this phrase? " Both methods require a stickered load. "
Craig to construct vacuum to bakee a hybrid with pipes and the fan, it is possible but speed of drying will be standard!
We have restriction of a conclusion pair from drying, çÿ the account of the area of gathering of a condensate. To increase the area we lose pairs and we lose of temperature in the chamber!
When I have understood it I did(made) a dryer without vacuum for drying a pine and other breeds of a tree, the post is lower than this forum.
The central pass to a stack improves movement of air but if it(him) is not present then drying will increase on couple of days.
I always speak that if you want speed of drying for " small time " it not to " Vacuum plus " if you want quality of a wood without a marriage(spoilage) then address to " Vacuum plus "
Sergey.

[Den Socling]

Sergey,

When you make spaces for airflow between layers of wood, you often use small pieces of wood which we call "stickers".

I'll have to work on translating your post when I have time.  ;) What I'm thinking is that the trough that you use under your condenser could double as a baffle. If the operator didn't want to depend on natural convection, he might energize fans under the trough to use the same air flow pattern that you use.

Den

[serg]

Den, thank for the answer.
It is possible to put fans, quickly to get warm a stack. A prize 2-3 days. Fans in Russia frequently break. America does(makes) good fans, it is possible to put. I see you really with good mood concern to my idea and a design of the drying chamber!
I from the bottom of the heart want to do(make) good work, the price - quality!
Your idea is always interesting to me Den! 8)
When you and other experts will come to Russia? The market waits for you. ;)
Sergey.

[boardwalker]

Den & Seregy

So you are saying I should still leave a gap in the middle of the stack. How wide should this gap be? What size pipe and how many feet do I need for heating tubes?

Thank you
Craig

[Den Socling]

Craig's fans will probably break but he can get new ones.  ;D

Sergey, how wide should the gap in the charge be?  :P

Craig, I would not run back and forth with bare pipe. Go to a local plumbing supply and ask for copper fin-pipe. It will get bent up and look ugly after a few months but it will work much better. Make manifolds and run parallel pipes. Get the BTU transfer rate from the supplier and we can calculate the required footage. If you want to try some trick, feed one side from one end and the other side from the other end. Maybe you will get a spiral air-flow to assist uniformity.

Sergey, I'm not planning any trip to Russia. If I go anywhere this winter, it will be to a tiny Caribbean Island that barely has electricity. With a snorkel, a towel, my wife and some beer.

Den

[boardwalker]

Den

I all ready have the specs for the copper fin tubes since that was what I was planing on using oringally. Scroll down through the link below and you will see a chart for btu out put according to what the input water temp. is. I know the 500's(1/2") have a higher output than the 750's(3/4"), but I can get the 750's for a cheaper price.

http://www.sterlingheat.com/litlibrary/HAC-5R.pdf

[serg]

boardwalker work with Den. The big professional.  8)
I badly can speak after English  :Pis can result in impasse of manufacture of the vacuum drying chamber.
Den to you will help. 8)
It is a pity Den, that we never have meetings!  :-\
Sergey.

[boardwalker]

Den

The way I had it figured before I needed 7000 + btu's per hour. So I was planing on running three 10' tubes which would have given me around 15000 btu's. Does that sound about right? My chamber is 11' 6" overall length 0n the sraight sides.

Craig

[Den Socling]

Craig,

I was looking a previous posts. Looks like you calculated 500bf.  I didn't do any calculations but if that fin tube can deliver 15,000 btu's, you're good.

Did you see that diagram a while back that showed the air flow in a Sergey kiln?

Den

[boardwalker]

I remember some diagrams but I thought they were for the discontiuous kiln. I know that in Sergey's kilns the cold air goes down the center below the condenser and the warm air goes through the stack and up the outside.

Do you have a link to which post Sergey's diagram was in?

[boardwalker]

Den

I guess I was a little high on the btu's for 30' of finned tube. It would be more like 12,000 btu's. Will that be enough or should I figure on 40'?