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Dr. Bob's multi purpose curing chamber in planning

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DrBob

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Dr Bob and Leverhead or anyone, here is a good question. could you, or would it work heating the kiln by infrared. I still love the crock pot, but it is an interesting if it would work.

Markw

sure. btu's is the answer regardless
 

DrBob

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I put a bunch of useful stuff in "Leverhead's Flue Cure experiment " post #79. In one link there, there's a pamphlet that goes into loading density and pressure to get a given airflow. You want at least 1/2 cu/ft of air, per pound of green leaf, per minuet.

seems high. meybe 10% of that would be my guess. 5 cfm per 100# sounds more reasonable. but I am just guessin
 

leverhead

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thanks mr leverhead. evaporation should be 144 btu per pint/or pound of water. ventilation is the wild card here It is t minus 7 months before the first test run of my chamber. YOU know a lot more about flue curing than me. You done it! I am just talking about it.

There's still ALLOT I don't know! I think by the end of the season we can all pitch in and write our own book. I don't know the size of your freezer, but you might bet a little heavy on the watts to leave room for cycling and unknowns. I think a dimmer switch is good for 600W, having one inline to the heat will let you keep the inlet temp in line with your needs, with maybe a once or twice a day adjustment. For vent losses, 1/4-1/3 of the moisture can be removed during yellowing. The air removing that moisture at that time will be below 105 F and roughly 85% RH, so the heat lost there should be the total of box loss + the heat to raise the replacement air temp + heat of vaporization of the water to get the replacement air up to 85% RH. If green leaf is 80% water and 100 Lbs of leaf goes in, 20-25 Lbs of water can be removed in the first 48 hrs., a little better than 1/2 Lb per hr. Calculate away!

I don't think stirring up the air will get good results, you need an airflow. Even the old barns operated like Deluxestoggie's cozy can, air came in at the bottom and left at the top. It was done at a low loading density and low speed, natural airflow. It was also a once through system, the air didn't recirculate. Recirculating the air lets you add pressure, that lets you put more tobacco in a given space, that lets you get more profit without adding facilities or it lets you keep more of your garage for other things. The right combination of parts and size to suit the home grower's budget and still get the job done is the real challenge.
 

leverhead

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seems high. meybe 10% of that would be my guess. 5 cfm per 100# sounds more reasonable. but I am just guessin

That pamphlet and it's recommendations came out in the middle of a patent fight. As I saw it, somebody tried to patent the flue-curing process as a way to reduce TSNA's. It all seemed to center around defining the airflow required to reduce the formation of TNSA's by bacterial action (Barn Rot). I was going over 1/2 CFM per Lb, I don't know how much, it didn't seem excessive.
 

LeftyRighty

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In 4 years of growing, I've never weighted any green leaf, so I don't have a clue. What's a big YTB or VBL leaf weight?
 

DrBob

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In 4 years of growing, I've never weighted any green leaf, so I don't have a clue. What's a big YTB or VBL leaf weight?

Green or dry? Yours or mine? I bet bigbonner knows..... if I had to guess I would guess 3 oz green 1/2 oz dry. but that is a wild guess.
 

LeftyRighty

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based on what's been stated so far, there seems to incentive to recycle hot forced air from the top of the freezer box, back to the bottom, in a manner that would allow moisture to condensate out and drip away. I gotta think about this!
 

DrBob

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based on what's been stated so far, there seems to incentive to recycle hot forced air from the top of the freezer box, back to the bottom, in a manner that would allow moisture to condensate out and drip away. I gotta think about this!

how about an air to air heat exchanger commonly used in new houses. they are great dehumidifiers
 

Markw

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how about an air to air heat exchanger commonly used in new houses. they are great dehumidifiers

Something like a condensing boiler flue like a pipe in a pipe . I have seen someone use twin wall polycarbonate as a heat exchanger in their kitchen, hot air would exit through the bottom, and fresh air came in through the top. It worked very well
and was inexpensive to make.
 

DrBob

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thanks Mark I have seen similar tube in tube air exchangers and they do pretty good.
 

DrBob

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tobacco 2009 132.jpgtobacco 2009 129.jpgtobacco 2009 136.jpg
The photos are of my curing chamber during construction. the vent tube and valve, the reskinned door and the thermostat mount. The thermostat is inside the chamber and will need to be replaced with a probe for a programmable thermostat. The vent tube is pvc and may have to be replaced for flue curing, time will tell.tobacco 2009 139.jpgtobacco 2009 118.jpg The vent hole in the bottom of the chamber originally had a metal valve which I found not necessary the last photo is the plastic shelf panel on the door just after it was cut off I suspected to find cardboard behind it and I did.
 

LeftyRighty

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All this heat exchanger (air-to-air or pipe in pipe) is a little more complex that what I was thinking. This photo is just a mockup of my thoughts, amateur as it is.

IMG_0228.JPG

Just a 4-inch duct from the top of the flue-chamber, down to the bottom, with an in-line duct fan at the bottom blowing into the chamber – maybe one duct-assembly on each side of the flue-chamber freezer box. At the bottom is a T-section, open on the bottom.

The fan sucks air from the top, blowing it back into the chamber at the bottom. The open end (bottom) of the ‘T’ would be covered with a muslin-cloth or canvas, limiting fresh-air intake. During the yellowing phase of curing, there will be at least a 10-20°F temp difference between the chamber interior and the outside ambient or room temp. That should be sufficient to cause condensation in the duct, running or dripping down to the cloth cover, where it drips or evaporates away. This system will keep the air moving in the chamber, and allow for removal of moisture over time.

Of course, this could be augmented with a normal (?) air exhaust pipe and valve on top of the chamber to help control RH.

I would just shut off the fan during the drying phase of curing, and hope I don’t lose too much heat by convection/conduction in this duct system.

What is shown is metal ducting. I used that because that’s what I had available to build this mockup. Metal duct would lose heat too fast, and lead to excessive condensation. I would probably build this with thin-wall PVC/ABS 4” pipe, or go el cheapo with flexible clothes dryer duct.

The in-line duct fan could possibly be:
http://www.homedepot.com/h_d1/N-5yc...ngId=-1&keyword=inline+duct+fan&storeId=10051,
or it could be a computer fan, or custom-built fan in a box to fit the duct. The referenced fan has capacity of 65 CFM free air. This CFM will be substantially reduced by the length of duct, 3 elbows, and pushing air through the leaf density.- perhaps I’d need a 6” or 8” fan with a reducer to the 4” duct. Trial-and-error ???

I’m still trying to get a handle on this ‘leaf density’ and ‘lbs per sq ft of leaf’ stuff.

OK, now tell me what’s wrong with my system, and what could I do better.
 

LeftyRighty

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thanks....but there are still a lot of questions, as:

Sizing the fan, how many cfm, and how much static pressure to overcome, and how do I compute the static pressure created by a leaf mass? Are there fan curves/charts for these little inline fans?
Do I need diffusers inside to distribute the air?
Does the air short-circuit inside – go around the leaf rather than thru the leaf mass.?

Based on the guide numbers on previous posts:
The foot print of freezer box is about 24” x 30”. Am planning on 2 rows, 24” long, allowing for 15”wide leaf. Enough height for 2 stacked rows of leaf. Total of 4 strings, 2 ft long, or 80 lbs of leaf – seems high. Thus 40 cfm of circulating air (or would that be 20 cfm since they’re stacked?)

If I get too much moving air, do I need to worry about drying-green leaf?
I also question if the numbers for a big barn are applicable for a small chamber.

Will this work or is this just a neat idea on paper? I’m thinking I’ll just have to guess and build it, and see what results I get. I wish I had green leaf to practice with now. Leverhead & deluxestogie are the only ones that has practical experience with big clumps of leaf mass in tight chamber.
 

leverhead

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OK Lefty, from your pictures, I think you're on the right track. It'll be a few days before I can get to take pictures of how I handled it. You'll want some kind of positive control of the vent. Is that single wall stove pipe? I really like the idea of condensing water out, I didn't do that, but I like the idea! Keeping the RH and the temp under control might end up being too much trouble compared to the cost (in heat) to just controlling the RH by venting. The leaf (loading) density is in Lbs per cubic foot. The numbers quoted are for bulk container loading as opposed to rack loading, there's some videos on youtube I need to find the links for that show both ways pretty well. If you look at the pictures later in my flue-cure experiment, I used more like a rack system. All the stems were oriented up rather than random as in a bulk system. The bulk system is a box with one side removable, it's about 6' tall X 7' wide X 2' thick. To load it they lay it on it's side and take off a 6' X 7' panel, lay the leaf in randomly orienting the stem in horizontal layers by weight (pounds per cubic foot of the box). Then they put the panel back in place and put steel pins (looks to me to be re-bar) in through holes in the box to hold the load in place when the container is placed back upright in the "barn" (kind of looks like a shipping container). The total pounds in the box determines the CFM of air that needs go through the box and how tightly it's packed (pounds per cubic foot) determines the pressure it will take to get the CFM. The only reason I'm even bothering with bulk curing is the only good data I can find is for that. I haven't found anything useful for rack systems, so I'm using it as a guide to make better guesses.

Now that I'm thinking about this, this thread is great. The last couple of runs I made were 6-7 pounds (green weight) of leaf per square foot of floor space inside the fridge, per layer of racked leaf. My fridge is tall enough to put two layers of racks. I think, I need to go back and look, I had about 600 leaves in one layer (about 100 Lbs) in a 3' X 5' floor space. So each layer would do 200 plants on a three leaf priming.
 

leverhead

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"Do I need diffusers inside to distribute the air?
Does the air short-circuit inside – go around the leaf rather than thru the leaf mass.?"

It can! Evenness of loading is important, I don't think a diffuser is necessary, with any back pressure at all, the space underneath the leaves will have an even pressure.

" Thus 40 cfm of circulating air (or would that be 20 cfm since they’re stacked?)"

1/2 CFM per pound of leaf.

"If I get too much moving air, do I need to worry about drying-green leaf? "

If the RH gets too low.

"I also question if the numbers for a big barn are applicable for a small chamber."

I think they would if the leaves were loaded the same way (container or bulk loading), the only place to fudge would be thickness (height) of the mass of leaves that you had to move the air through.

" I wish I had green leaf to practice with now."

I was at the same point last June, it's a bitch to have to plan on thinking fast. I made mistakes and had the weather against me. I haven't revisited this stuff for a while, keep asking questions and I'll keep thinking about the answers.
 

DrBob

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When I built my curing chamber for ferment curing I estimated a need of 6 air changes per day. Or 1 air change in 4 hours. My chamber is 26 cubic ft so it worked out to roughly 7 cubic feet per hour. I measured air flow by putting a super thin plastic bag (dry cleaner bag) on the exhaust stack and measured the time it took to fill the bag with hot air. Kinda crude but I got a good idea on where to set the bleed valve. It was a lot of dickin around but I learned a lot about how the chamber would perform before I put in my precious tobacco for curing.

In the real world I used the bleed valve to control the humidity in the chamber. The thermostat controlled the temperature and I adjusted the humidity level by controlling ventilation. More airflow= dryer chamber less airflow= wetter chamber. I measured humidity by feeling the leaves in the chamber if they felt too dry I reduced the air flow if it felt too wet I increased the airflow. I also adjusted the chimmeny length to optimize airflow. I left it at 24" and that seemed to work best. The bottom line is GO BY FEEL!!!

Now I want to change this chamber to a flue curing chamber. We have a whole new ball game. The only value we need to know is how many air changes per day. Guess what More air changes = getting dryer faster less air changes = getting dryer slower. The rules are the same, the temperature is controlled by the thermostat the humidity is controlled by air changes again.

Leaking out too much air costs money.
 
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