Purchased tank to make into vacuum kiln

[boardwalker]

I am hoping that Den will help us get this dis- continuous vacuum kiln topic going so that I can try drying some wood in this tank. Den I was here when this topic got started and tried to participate in the discussions, but could not try building one back then. Back then I was bowl blanks and more, but I losted my password and had to sign up again. I printed and reread all the posts that I could find. I understand the concept and would appreciate any help you could give me. The straight sides on the tank are 11' 6" and the inside dia. is 40". I have been having a hard time finding a 2 hp 2 stage liquid ring pump. I can find lots of larger pumps and smaller single stage pumps.

[beenthere]

boardwalker
Is that the same technique use by Den and his company?  If so, seems it would be tough for a guy building and selling vacuum kilns to help someone build their own. Maybe this isn't the case, but seems it might be a problem.
Doesn't stop others from filling in the blanks, but there are'nt too many experts in the area, me thinks.

Don't get me wrong, as I 'd like to see you build one and test it out. May or may not be less expensive than buying one.  :

[boardwalker]

photos hopefully

[boardwalker]

beenthere

This is a different concept than what Den uses. Den uses continuous vacuum. Den was trying to help us get a dis-continuous vacuum kiln built awhile back and I am hoping that he is still interested in the project.

[beenthere]

Gotcha. Thanks for the clarification.
That cylinder looks like a good start. 

[Den Socling]

Surely I will be glad to help. I haven't had much free time lately but this design can be reasonably simple. Remember Tyler? the guy who dried a table top for Jerry Seinfeld in a vac kiln made with a plastic bag? He wants to build a discontinuous vac also. But I just got done unloading a couple mbf of 12/4 table tops to dry for him. He's behind schedule in building his kiln.  :D

Your chamber does look like a good start. Got a welder to add a couple nipples? When you are done with welding, you may want to coat the inside will coal tar epoxy.

[boardwalker]

Den

How many cords do I need to run through the tank wall? I have a 2" threaded coupling on the back end cap and 3 more across the top plus 4 or 5 1/2" to 3/4" on the front end cap. I could just put reducers in these and save having to weld on the tank any more. I do have a welder and can add anything that you think I need . I work in maintance at a large plant and do this type of stuff daily. I just don't know much about vacuum and drying other than what I have been able to gather from you.

Would it be possible to buy a vaccum pump through you or do you know of a source where I can get a used one. I have a 2 hp motor so all I would need is the pump. From what I have read I think that you were saying I need to use a 2 stage pump to pull enough vacuum.

Where would you get the coal tar epoxy?

Thanks
Craig

[Den Socling]

You will need to get heating water in and out. For a chamber that size, 1-1/4" would do. You need to get power for circulating fan(s) in. You need to get some tiny wires for RTD's into the wood. The idea is to heat with no vacuum by circulating warm air. Circulating evenly is the hard part. Heat until the wood is sufficiently warm and then pull vac until you have used the heat. Then repeat the process.

The little 1-1/2HP 2-stage pumps from WoodMizers would work. We sell SIHI's but I have new ones, only.

Coal tar epoxy is available at many suppliers, like Grainger.

[Furby]

Coal tar epoxy
What is it and what is it's use?

[Den Socling]

I'm not a chemist but a fab shop told me they use it in liquid storage tanks. I've tried it in a couple carbon steel chambers it it seems to work well. Not as well as stainless but, if you have a carbon steel chamber, I recommend it.

[boardwalker]

Den

What size hole do I need for the vacuum pump, and do I need a whole in the bottom of the tank to drain condensation or is all the moisture taken out through the condenser between tank and the vacuum pump? Also, does it matter where the hole for the vacuum is located?

What would a new pump from you cost? Do you know where to locate any of the Wood-mizer pumps?

I was also wondering if I should insulate the outside of my tank to keep condensation from forming on the walls and rusting it out? Just remembering that Serg's system used insulation and didn't have rust problems.

I was thinking of using a fan at each end with baffles and the heat exchanger down one side of the kiln like Vacutherm used. Is this a good idea?

Thanks
Craig

[Tom]

I wonder what that "paint on" pickup bed insert stuff would do inside of a kiln?

[Den Socling]

Craig,

A 1-1/4" NPT nipple would be a good size for a vacuum connection. You will need a nipple about the same size in the floor because water will always be condensing on the chamber, even with insulation. I don't think the location of the vacuum port would make any difference. The floor drain can double as air-bleed back into the chamber.

A little SIHI vacuum pump in bronze mounted with a motor cost around $1500. The size of the vacuum pump isn't as critical with discontinuous as with continuous vacuum drying.

Sergey's chambers don't rust because he has heating water pipes on the chamber. Condensation occurs at a condenser at the ceiling.

That air circulation could work but a lot of attempts have been made over the years to get perfectly even circulation. It is apparently difficult.

From what I'm told, coal tar epoxy is 'self healing'. If a tank flexes, it does not crack and break lose. I bet the truck bed stuff works the same way.

Den

[woodhick]

boardwalker, I am watching this thread close as I may  want to build one myself.  What was your tank used for in its previous life?  It looks to have some serious corrosion or rust pitting on the side.  Do you think it will hold up under vacum?  Good luck and I hope to be right behind you with a kiln of my own.

[boardwalker]

Den,

How big is the vacuum pump that you quoted the price on? I was wandering because in the future if this works I was thinking of possibly running 2 kilns side by side or possibly a larger one.

I thinking that I need to get a pump purchased so that after I get finished welding the rest of the fittings on the tank I can run a vacuum test to see if I have any small pin holes that need to be patched before I paint the inside of the tank.

I was thinking the other night about the air circulation system and I thought that another way would be to use a fan wall similar to a dehumidification kiln using a row of tangential blowers right in the top of the cylinder with aluminum finned tubes all along the front for the heat exchanger. These fans are low cost from the surplus center and I think that by having them spread all the way across the top  and the bottom of the kiln charge blocked off so that the air would have to go through the stack your air flow would be spread about as evenly as possible.

How many cfm do you think it would take to move enough air through the stack. The fans are 7" to 10" long  by 3" to 4" square. I figured about one per foot for a total of ten or eleven. Surplus Center has these from 29 cfm to 90 cfm $8 to $20 each. The largest only pulls .56 amps/110 volts the small ones pull .10amps/110volts.

[boardwalker]

Woodhick

I think it was a anhydrous tank like they use to apply ammonia in the gound behind a planter. I think they removed the wheels and letf it on the ground for awhile before they decided to make it into a vacuum chamber or whatever they had in mind. I bought it for $25 at an auction. The tank sides look to be at least 5/16" so I don't thinkthe rust will be a problem.

[Den Socling]

Craig,

That SIHI is 3HP, 30CFM at 49 Torr.

One of Maspel's (VacuTherm) designs used a wall of fans but, incredibly, mounted the motors outside to avoid the harsh environment.

I wouldn't think that high velocity is needed. The air isn't carrying away water. It's delivering heat.

$25!! That tank would be worth more than that as scrap metal.

Den

[Jason_WI]

A vane vac pump from a milking system would work. Universal dairy systems uses this kind of pump. Dont use a figure 8 vac pump(boumatic) as these will lock up with water vapor. My dad bought a 7.5 hp pump for 200 bux. It draws 100 cfm ad can pull to at least 29 " mercury unregulated.

The only thing bad with these pumps it that they require a oil drip for the bearings. If you can look for one with a oil reclaimer system.

With 10 dollar milk these pumps shouldn't be hard to find.

Jason

[boardwalker]

Den

How many btu water heater do I need to heat with? Would a 50 or 60 gallon propane water heater keep up with the demand?

I guess I'm trying to decide between 10 29 cfm fans or 10 50 cfm fans that I could possibly regulate with a ceiling fan speed control.

What series Worcester valves were you using with the Belimo actuators?

Is it nesessary to use a check valve on the vacuum line if this is a dis-continuous system?

[Den Socling]

Craig,

Sorry that I don't answer more quickly but I have been busy. I'm here now because a shipping container is late.

Depending on species, wood can have 3 to 5 gallons of water per 1% per 1000 board feet. It takes about 8114 BTU's to vaporize a gallon. So, estimate the amount of wood you will have in the kiln and you will be able to estimate total BTU's.

Belimo supplies actuators on valves so there is no messing around with mounting and coupling.

No check valve is required. I suggest that you operate manually until we see what kind of bugs are in the system. If it dries as planned, everything can be automated.

Den

[boardwalker]

Can someone check me on my math?

My kiln will hold about 468 bdft so I am going to use 500 bdft to figure how many btu's of heat I need.

Say we need to remove 60% moisture.

I'm figuring this for 2" thick lumber so say that it takes 14 days to remove the 60%.

60% / 14 days = 4.28% per day

Assuming that we are heating for 12 hrs and vacumming for the other 12 that leaves us 12 hrs to vaporize 4.28% moisture.

4.28% / 12 hrs = .35% moisture per hr of heating

Assuming on the high side 2.5 gal water per 500 bdft per 1% moisture

.35% x 2.5 gal = .9 gal of water per hr

Den says it takes 8114 btu's to vaporize 1 gal

8114 x .9 = 7303 btu's per hr

So if I calculated everything right a 30,000 btu water heater will be more than enough.

Thank you
Craig

[Den Socling]

more than enough, as you say. Even when you add losses. Unless your chamber is sitting in Alaska.  :D

[boardwalker]

Den

Is my figure of 14 days for 8/4" within range of this kiln?

[Den Socling]

most species yes, some no

[wiam]

I am wondering if I could do this on a smaller scale.  I have an old Zero brand milk  bulk tank.  It is 350 gallon capacity.  It is a vacum tank.  Meaning that the tank was under vacum when milking the cows.  My question; would running hot water through the freon lines work for the heat?

Will

[boardwalker]

Den

What should the air temperature inside the kiln be? If I'm running 180 degree water through my heat exchanger will the air temp. get to high before the wood gets up to it temp setpoint?

Can you pull to many cfm of air by using to big a pump?  I have a lead on a nash or elmo/ 2bv2 070 or L200 that can pull up to 60 cfm but as far as I can tell pulls about 35cfm at 50 torr. It uses a 4.5 hp motor but it will take a long time to equal the cost savings in electicity that a smaller 3 hp would give me.

Thank you
Craig

[Den Socling]

Will,
I know nothing of milk storage tanks. Jason?

Craig,
Safe temperature depends on humidity. Hot dry air will damage your wood if the wood is wet. Hot humid air will not damage the wood unless it has already seen some damage. I'm guessing that you would want humidity high with air temperature around 115-120 while there is free water in the wood. However, in steaming experiments, I have heated green wood like cherry and walnut to 140+ with high humidity and then pulled almost all free water out with one vacuum cycle in a few hours. This put a few small end checks in 8/4 but the process seems very forgiving if you are working with a porous species.

The vac pump can't be too big. It will turn on and off with wood temperature. The bigger the pump, the less time it will be running.
Den

[boardwalker]

Den

How do you keep the humidity high if you are sucking the moisture and air out of the chamber with each cycle? Do we need to include so sort of humidity sensor in the control circuit, or can the vacuum pump not remove all the humidity before the temperature of the wood drops back below the set point?

Thank you
Craig

[Den Socling]

When you are heating with no vac, humidity will rise in the closed container. When you pull vac, the atmosphere will remain humid, though less, from water boiling out of the wood.

[Jason_WI]

Wiam,

Bulk tanks normally don't see the vacuum of the milk system. This is uaually isolated at the pump that transfers the milk from the receiver to the tank. I am pretty sure if you pulled 28-29 "Hg that the tank would suck flat and shrinkwrap your load of  lumber in stainless steel.

Jason

[wiam]

Jason there was no reciever.  The vacum line connected to the tank through a moisture trap and the milk line went into the tank.  No transfer pump.  I realize that the tank has only had about 15" on it but I was just thinking.

Will

[Den Socling]

What happened to this thread? I thought we were going to carry through this time. I've built two vac kilns since it was started.  ;)

[serg]

Den hi!
This string good. Should will be filled with new technologies of vacuum drying.
Have started the vacuum drying chamber of 30 m3.
Has checked up Vacuumterm look result under the reference.
Sergey.

http: // trans.voila.fr%20www.vacuums.ru%2Findex .php%3Fid%3D7|child_id%3D29

[serg]

To look this reference.
Sergey.

http: // www.vacuums.ru/index.php? id=0*nid=11*child_id=18

www.newkilns.com

[boardwalker]

Den,

I have been working 10 to 15 hours a day 6 days a week  so I haven't had time to think about this project for the last month. I thought I had some vacuum pumps purchased, but when the guy went to ship them he found that the pumps were cracked. I haven't been able to locate another used pump for a decent price so I may be back to buying one from you. After the first of december things should slow down so I can get back on the kiln.

Craig

[boardwalker]

Den,

What is a Sihi LOHY2704 vacuum pump? It's being advertised as a liquid ring vacuum pump, but I cann't find any information on Sihi's web site.

Craig

[TexasTimbers]

What happened to this thread? I thought we were going to carry through this time. I've built two vac kilns since it was started. ;)

I can't build one right now too many irons in still, but I can ask stupid questions. I have four 250 gallon propane tanks I could weld end to end making a chamber (rough guess) 36" x 18 feet long.

It would not make for many BF but it would be good for high value specialty stuff below the 8/4 range wouldn't it?

[Den Socling]

Craig,

I searched with Google and found this.
Pas de photo disponible
Inventarnummer :    97145
Kapazität :    26 
Kategorie :    Pump / Vacuum
Beschreibung :
26 cfm @ 25"Hg, Sihi 316SS vac pump. SN 3160407, Mdl #LOHY2704. Packing gland. Direct driven by 3 HP, 3/60/230/460 volt, 1735 rpm motor, UL label. 1 1/2" inlet x 1 1/2" outlet. Base mtd.

[Hier klicken oder mehr Informationen anfordern]

It looks like a nice little pump.

kevjay and all,

Lets see how Craig's system works and what kind of snags might be encountered by someone new to building vac kilns. And there is nothing wrong with joining tanks to make a longer chamber.

Den

[boardwalker]

Den

Will this pump pull low enough vacuum and enough cfm's? The specs are quite abit lower than the pump you were talking about originally.

Craig

[Den Socling]

Craig,
If it is 2-stage, it has the vacuum capacity. Little pumps don't have the cross-over pipe between stages and are difficult to distinguish from single stage. I can't verify from the pictures that it is two stage. As far as CFM is concerned, if the pump is low in pumping capacity, it will take you longer to use the heat that built up during the heating stage. Drying will take longer but the wood won't suffer. Also, SS pumps usually have lower ratings than the same pump in another construction.

I'm going to be drying 18" x 18" Doug fir next week so I will be experimenting with control ideas that I will give to you.
Den

[boardwalker]

Den

I got the pump and a motor. I fust need to buy a flex coupling to put it together. The pump is a new punp that has been sitting  on the shelf for how knows how long. Sihi no longer makes this model. I did manage to get some specs but the fax was so bad I could hardly read it. Will have to have them send it again. From what I could make out the pump will pull around 20 cfm at 50 torr. The pump appears to have some loose rust flakes on the inside from being stored for so long. Is this something I should be worried about or can I just rinse it out good and start it up.

I also have a circulator pump and loop controlers purchased. Have a couple of used water heaters that I think I can make work. If not I will have to buy one. Need to purchase my valves, fans, and  radiant heat tubes. Then I just need some time to start putting everything together which will hopefully happen soon.

Craig

[Den Socling]

Craig,

Common construction for vacuum pumps uses cast iron cases with bronze or stainless steel impellers. A little rust doesn't hurt anything. It is often necessary to break them loose before start-up. Then, if they are ever left unused, dump some antifreeze into the case.

Can you program the loop controllers for discontinuous vacuum drying? I was working with 18" thick Douglas fir last week and discovered that you can get the core of porous wood under 28% pretty quick but I then I screwed up the process!

Den

[Dave Shepard]

I am very intrigued by vac drying, even if I don't build one, although I will try, I would love to understand them better. I went to your website (Den), and noticed the kiln chambers were square. Is it simply a matter of putting the ribs on the outside to strengthen the chamber? If so, I could build a small chamber easily. I have a contact at an excellent machine shop that can bend up any size or shape rib I would need. It appears that the chamber is built similiar to a dump truck body, only it would work in reverse. I will be rereading old threads to try and figure out what parts make up a vac kiln. So far I know we need heat and vacuum.  :D If I want to go automated, what do I need to control the kiln, a PLC? Just thinking about vacuum, the ski area I used to work at has seven 1200CFM Fuller rotary vane compressors, which can also be used to make vacuum. That would dry a lot of wood. :D Can you run 2100HP of electric motors off of a phase converter? ;)


Dave

[boardwalker]

Den,

I have not tried to program the controllers yet but we use similar ones at work for controlling heating cycles in our ovens.

What happened to your doug fir that you were drying? That is some really thick wood.

Craig

[Den Socling]

I like rectangular chambers for a number of reasons but cylinders are easier to find. A carbon steel support frame over a stainless steel chamber is the design.

PLC's used to be finicky and I preferred loop controllers. Now, however, PLC's are dummy-friendly and we get along.  :D

The Doug fir turned into a very interesting experiment. It verified some of what I guessed and some new ideas developed. It appears that 18" squares can be dried very quickly and easily but I can't say anything about the details at this point. The report is being reviewed by the patent guys. The basics are as I always said about discontinuous vac. Monitor the core temperature of the wood and use that temperature to control chamber pressure.

[Den Socling]

 I thought I knew the exact settings to get those 18" squares dry and so I expected some 12" squares of Douglas fir to be easy. The experiment failed miserably!  :( Back to the drawing board. But I still think discontinuous vac should work well with most species cut to lumber.

[boardwalker]

Den

If I run a condenser on the vacuum intake could the seal water be used for watering cattle or would there be to many contaminates from the drying process?

[Den Socling]

Craig,

Only a CSI lab could say for sure. But why not cool the water and use it for seal water again?

Den

[boardwalker]

Den

I guess I am having a hard time finding a cooling tower that doesn't cost alot.

[boardwalker]

Den

Would one like this work? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290067823991&fromMakeTrack=true

Can you bring the water temperature back down to 60 degrees with a cooling tower?

[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'?

[boardwalker]

Den

I found some drawings of the air flow for Sergey's kiln, but there were 2 different oppions and it was never clarified as to which was right. her is the link.

My opinion:
http://www.infolida.com/rerednaw/kiln.gif
Den opinion:
http://www.infolida.com/rerednaw/kiln2.gif

[boardwalker]

Den what will I need to tell when the air inside the kiln has reached complete saturation so that the controler knows when to start the condensing cycle? Also, should we have a pressure sensor for the vacuum pump circuit and if so what kind of sensor do I need for that?

[Den Socling]

I started looking for those drawings last night and ended up rereading a zillion pages about vacuum kilns. Sergey, you should speak English by now! with all the post you have made.  :D
Then I got a message from the CEO of PCS VacDry reminding me to keep intellectual property confidential.  :( How timely!

Let's see what I can say. I believe cool, dry air drops down through Sergey's kiln charge, through the stickered wood and up the sides. If you didn't want condensing, you wouldn't have much air flow. I think it should have a little boost.

I would lean toward too much fin tube to avoid the chance of too little.

You could add a RH transmitter if you want to control humidity.

Pressure transmitters are available. One in the range of 0 to 760mm Hg. Take the voltage or current output, put it through a loop controller and give the loop controller engineering units of 0 to 760.

[boardwalker]

Den

Will an rh transmitter work with a loop controller to control the heating and condensing cycle or do I need a special controller?

[Den Socling]

You can get RH transmitters with standard outputs like 4-20mA or 1-5VDC. Put it into a loop controller and scale 0 to 100.

[boardwalker]

Den

Should the heating cycle shut off when the condenser is on or should it just be controled by a thermostat or an rtd in the wood?

[boardwalker]

Den

I have a pressure transducer and a humidity transmitter located that should work good. Looks like I will need 3 loop controllers. 1 for the heating, 1 for the condensing(humidity)control, and 1 for the pressure control.

So my cycle is turn the heating circuit on, turn the vacuum circuit on. Run the vacuum pump till the pressure transducer reaches its set point(which is ?) ,run the heating till it reaches its set point which will be controled by rtd's in the wood, and run the condensing cycle which will be controlled by the Rh transmitter(100% rh turns on the condenser ?% turns the condenser off).

Does this look right? Now all we need to figure out is where all the set points should be).

With this type of a system I don't think I should need a cooling tower since the vacuum pump will not be running very much.

Anymore input before I finish buying the rest of the parts?

Thank you
Craig

[Den Socling]

With discontinuous vac, you heat with atmospheric pressure. This means there will be plenty of air to circulate and carry the heat from your fin pipe. I would control vacuum from wood temperature. Heat with no vacuum until the wood is warm then pull vac until the wood is cool. I would leave humidity run high.

With Sergey's method, you have lower pressure in the chamber but there is still enough air to circulate heat. If I remember correctly, I translated around 200 -250 torr from one of his post. Then you would need the condenser is assist airflow.

Yep. Three loop controllers and you should be able to use either process.

[boardwalker]

Den

What is the boiling point of water at 250 torr?

[Den Socling]

Around 160'F but you don't have to boil water to dry wood.

[boardwalker]

Den

I know this drawing is small I couldn't get things to work right, but if you can see my arrows does the air move through the kiln like it is drawn on the left where the cool air drops through the center and is pulled through the stack to the heating coils as it drops and then back up the outside to the fanwall under the condenser drain, or does it move like the right side of the drawing with the cool air dropping down the center and coming up the outside and then through the stack to the center and up?



I'm still thinking of using some tubing runs along the outside of the tank for extra btu's plus the added benefit of not having condesate on the tank walls. Do you think this is a good idea?

Can you tell the moisture content of the wood by how high the maximum humidity is inside the chamber or how do you know when the charge is dry? I guess I was thinking that since lumber will equalize at a certain moisture content depending on temp./ humidity that you might be able to tell the moisture content of the charge by how high you can push the humidity inside the chamber.

[Den Socling]

I think the air flow is as shown on the left. That would make it depend on a drop in humidity. That's why I think some fans blowing down would assist. What do you think, Sergey?

I think that, if you add extra tubing, you should put it inside. If you keep the steel of the chamber warm, it will stay dry.

When the wood is dry or has reached EMC, humidity will drop. At the same time, you will stop dumping condensed water.

[serg]

Den.
I against the fan. I build drying chambers without fans. Fans a problem as drying a wood.
I learn(teach) to dry a wood - humidity 6 +/-0.2 % a stack, thickness, length of a board. All exotic breeds of a wood.
The fan to apply in drying result gives badly. Speed of the agent of drying vacuum a dryer and DH a dryer 0.3 m / second.
Such speed of the agent of drying allows me to not cover an end face a board a paint mastic!
Den advice(council) I can not give.
Sergey.

[boardwalker]

Den

Will I still need the shell & tube heat exchanger for a condenser in the vacuum line if I'm going to use the cold water pipe and chute it the top of the chamber for the condenser?

[Den Socling]

Yes. If you are drying something that is easily cracked, you will want to leave humidity in the chamber high. That's when the pump condenser is needed.