reefers for kilns

[starmac]

I may be wrong, but I thought all refers had an aluminum floor, no matter what the walls were lined with.

[jaciausa]

I always thought my units were stainless on the floor, I need to go check the serial number and find the specs. Also take a magnet. I am in the process of finding another reefer trailer and I have found one with 3 side doors that is aluminum. I believe in any case I can retrofit and come out well ahead. I plan on spraying the foam and covering or using r board. I would already be started but received loads of dry lumber this summer that I need storage for. Any advise on the insulation or other is appreciated. Thanks

[jaciausa]

I am now sure that the floor and the outside must be aluminum. They did a fantastic job polishing the outside when this was built. It will just be another obstacle to contend with. Would ERC be any more corrosive then white oak, and are there any more woods that would cause problems?
Insulating the floor from the top and using a taller inverted track could work, but that gets me  to thinking that building from scratch would be the best option! Any steel placed inside also would corrode from the moisture.

[mike_belben]

Paint it.  Works on bridges and battleships.

Btw stainless is nonmagnetic other than 400 series.

[YellowHammer]

Steel will rust pretty bad in a kiln, galvanized steel even worse, but I don't think aluminum is in any real threat from corrosion failure in a kiln. 

I have two Nyle kilns, and both of the chassis of the units appear to be constructed of aluminum sheet metal maybe 1/8" thick.  Nyle wouldn't use it if it was a significant problem.

Also, I know the floor runners I can see are extruded alumimun and is one of the reasons I bought the reefer.  This structure makes the floor dead flat, and I look at it every time I load and unload the kiln, and I have seen no degradation at all.  It looks as good as the day I put it into service, more than two years ago.  In that time, I have had it running 24/7 and pump a load out every 7 to 9 days.

I would not hesitate to build more of these, they are maintenance free, and work extremely well.  Due to the total lack of chamber degrade and zero maintenance I prefer it over my stick built. 

Reply #26 has some pics of the floor
https://forestryforum.com/board/index.php/topic,82071.100.html

BTW, eastern red cedar is a lot tougher on the kiln machine than the chamber.  When dried, it vaporizes some of its oils and it condenses in the drip pan as a white crystal mashed potato looking material, and clogs up the drip tube and sometimes the drip pan. 

[jaciausa]

I am glad I have the experienced help from all of you. My floor is not a duct aluminum floor, more of a continuous probably alum sheet metal.Metal only goes up about 18 inches on sides. The plastic coating most likely is glued on plywood- frp as it is fastened only on top/bottom. I am now going to use this the way it came, no insulation added except under floor. Outside probably is 300 grade stainless like one of you mentioned.
The food service industries use these type of trailers and many are available when they update there fleets. The units I bought were taken out of service because diesel emission rules outlawed there use in some states. Being a portable kiln could be a plus in some cases. It also means there are most likely some in every state ready to become kilns. Tell them its for cheap storage or they will up the price! 

[Cazzhrdwd]

Steel will rust pretty bad in a kiln, galvanized steel even worse, but I don't think aluminum is in any real threat from corrosion failure in a kiln. 

I have two Nyle kilns, and both of the chassis of the units appear to be constructed of aluminum sheet metal maybe 1/8" thick.  Nyle wouldn't use it if it was a significant problem.

Also, I know the floor runners I can see are extruded alumimun and is one of the reasons I bought the reefer.  This structure makes the floor dead flat, and I look at it every time I load and unload the kiln, and I have seen no degradation at all.  It looks as good as the day I put it into service, more than two years ago.  In that time, I have had it running 24/7 and pump a load out every 7 to 9 days.

I would not hesitate to build more of these, they are maintenance free, and work extremely well.  Due to the total lack of chamber degrade and zero maintenance I prefer it over my stick built. 

Reply #26 has some pics of the floor
https://forestryforum.com/board/index.php/topic,82071.100.html

BTW, eastern red cedar is a lot tougher on the kiln machine than the chamber.  When dried, it vaporizes some of its oils and it condenses in the drip pan as a white crystal mashed potato looking material, and clogs up the drip tube and sometimes the drip pan.

Same with mine, never had a problem with the aluminum floor.

[mike_belben]

I had a thought recently..  Maybe a bad one.  kiln wizards please chime in on this.  


How could one make use of the actual over the road diesel refrigeration unit to dry wood?  Lets imagine a guy with a working reefer box and no money or real serious need for a kiln, pertaining to firewood lets say, cant go all that wrong.. Not some lumber business with a credit line and high dollar flooring and a defined ROI. And definitely not a plan to spend $15k to make back $1500!  I have enough of those!  ;D



I think placing lumber into a walk in freezer or cooler would not work well or people would do it. Im guessing it would just condensate the entire interior and also the water molecules in the wood arent going to be very excited about leaving their cozy fiber home at low temps. 


What if a sizeable tin ductwork loop was suspended from the ceiling and connected between supply and return baffles of the unit, forcing cold air through the duct, with a plastic or tin drip catch pan style gravity drain system to handle moisture removal? I made many of these pans and panchos at smith and wesson for oil leaks in the basement ceiling that came through from the machining floor above so i know those are simple and effective at putting liquid in a bucket somewhere.

 

For circulation and heat i was thinking a variable displacement, belt drive hydraulic pump could go on the crank pulley and a closed loop hydraulic circuit be used to spin fans inside the chamber.  These parts are easy to come by from ride on or truck based sweepers.  Tennant, elgin, et al.  Plumbed in series with a variable pump, airflow will be controllable.  Individual fans could be turned on and off and all could run faster or slower.  


 The hydraulic cooler and engine radiator would go inside the chamber for cogeneration of heat for thr interior space, while the refrigerant condensor obviously stays outside.  Maybe a wastewood fired stove or boiler for initial startup/supplemental heat? 



Please leave the corrosion and insulation concerns aside, just wanting to discuss the merrit of these components.  One could use a refer unit on any custom enclosure if it could work. 

[mike_belben]

anyone?  @YellowHammer  @tule peak timber  @wooddoc 

[tule peak timber]

Just my 2 cents. I do have experience with custom electric and hydraulic driven systems for refrigeration in my past boats and they both work fine.
  Usually trying to reinvent the "wheel" so to speak when Nyle has it down to a science is going to cost more in the short-and long run. In addition when the inevitable problems arise there is history and knowledge available to solve issues from the known system technology.
 I do not mean to discourage you from "thinking outside of the box"Just my opinion. Cheers  Rob

[mike_belben]

I live in a camper because im that poor.   Im talking about making something from nothing like i always have.  Its not discouraging, just not any sort of option. 

[Southside]

Trying to visualize what you are thinking here.  Start the air loop at the top, it will be dry, hot air correct?  You say firewood, how will the air get down through the stack? After it passes through the stack how do you get the air over the condenser to get the moisture out? 

One thing I see that presents a problem is that you are always burning diesel to generate the necessary heat, and I have to think that reefer engine will cost more per hour to run than an A/C compressor.  In a closed loop Nyle kiln once the air is over 80F the waste heat from the compressor keeps the temps up, actually it can keep it too high and you need to dump air to stay in the right spot.  The compressor kicks on and off depending on the setting, so the electrical draw is pretty low.  

Airflow is what gets the moisture out of the wood, if you are just heating the whole stack and not getting velocity across the face of the wood then moisture removal will be slow.  

[YellowHammer]

For a workable kiln, all you need a little heat to warm up the wood, ambient temperature air coming into the kiln, a means for the wetter and warmer air to leave the kiln (vents), and a way to maintain the slightly warmer temperature continuously.  Air flow can be very minimal as the wood dries.

A truck reefer makes an excellent unsulated box.  Then a very small vent would be added at each end of the the reefer to allow the introduction of cooler, dryer outside air, and the expulsion of warmer moist air.

The vents would be small, because some sort of heat source would be required for the incoming air and you'd have to establish a heat balance where you could heat the incoming air at the rate you were expelling the warm moist air.  

Adding heat takes energy, and generally the simplest from a sawmill standpoint is from burning wood sawdust or waste.  The idea would be to generate just enough heat to warm the incoming air, but no more.

The heat would have to be supplied by a source, such as a radiator, heat exchanger, direct fire burner, diesel exhaust, etc.  The reefer ac units would have coils and such that could be salvaged.

If you simply expel the moist warm air, you don't need a chilled coil to remove the water from the air.  You just need to add ambient air.  Out with the wet and warm, in with the ambient and dry.

This would be a very simplistic system, and it would dry wood, not optimally, but it would work.  

I don't know if this helps you or not.  

[farmfromkansas]

I have a 48' reefer trailer, the seller removed the refer unit, and the wheels, and delivered it setting on the ground to my location, where we set it on some 4x8 prestressed concrete panels, one on each end.  The back 4' ceiling insulation was shook loose, and I cut into it, the insulation seems to be the same stuff they make Tuff-R insulation from.  Planned to replace the piece in the rear, using some foam adhesive and new Tuff-R braced up with some 2x4's, but haven't gotten around to it.  The thing works great as a solar wood dryer, I have a ready supply of dry wood now.  Downside is, I can't get it hot enough to sterilize, so any new wood will have to be coated with solubor. The trailer has fiberglass panels on the inside.  Heat limit 160

[scsmith42]

Mike, I think that your energy costs would be significantly more trying to reutilize a diesel powered reefer unit for a DH kiln, versus a Nyle unit.

One thing to consider is if you can decouple the engine from the actual reefer unit, and use shore power for it.  You could take the components and duct them so that incoming air crosses over the A coil with the drain pan under it, and then exits passing the condenser coil to heat it.

My experience with hydraulic systems is that they are not as efficient as electric, nor can you create your own electricity with a diesel generator as inexpensively as you can buy it.

Just some thoughts to consider.

Scott

[mike_belben]

I have 2000 gallons of vegetable oil in totes right now.  I convert mechanical diesels to straight veggie easily.. They cost me ZERO to run. They cost me very little to overhaul.   I am a fruitloop, normal person costs are not my costs so please lets just not talk money guys. I just want to discuss the physics of it, not the finances. 


@Southside  think of a basement with central AC ductwork hanging from the joists as usual.  Brand new install on a hot, humid summer day.  Flip the AC on and moisture condenses and drips off the ductwork.  

Now switch out the basement for a container full of wood.  Catchpans to collect and evacuate the condensate.  

My concept was not to cool the entire container, only the ductwork interior to make a chiller coil that removes moisture.  This would be very low load for a 3cyl reefer because its such a small air volume compared to what theyre designed for and it may even cause wet stacking.  I figured throw in the hydraulic fan cooling purposefully for the 20-30% efficiency losses that would create sufficient load for the engine to run well and waste heat that would be generated to warm the box while forcing the airflow through the wood using curtain baffles or whatever proves to be needed. Trial and error is the fun of it all IMO.   [Whats the fun in mortgaging my freedom to buy a perfectly functioning boring old nyle with zero bugs for me to enjoy working out, and have to actually work for money to pay it off ..honestly. ] 



@YellowHammer  

Yes very helpful, thank you sir.  While back I did build a small wood fired kiln that was very, very successful at drying firewood but also very likely to burn down so out came the burner tubes and its just a drying shed now with open vents top and bottom all the time.  Ive recently concluded that it dries lumber quite well over a summertime with no effort so that definitely supports your simple suggested layout.  Much simpler in practice than reading kiln build threads makes it sound.  


If a chilled condensate loop isnt going to rapidly speed the drying process i wouldnt waste my time.  I have need of a drive in, skid steer loaded firewood drying rig in the next year or two.  I also need to house an onan 4cyl diesel generator that will power the shop without excess noise killing the neighbors.  I will simply plan on putting the generator inside the can, properly baffled, and letting the radiator and exhaust cogen the heat and fan push the air.  I have a huge industrial heat exchanger made from probably 100feet of exhaust piping bent into a big sponge of tube that goes inside a big plenum.  I will run the exhaust through that before exiting the can and the airflow into the wood chamber will have to pass over the pipe exchanger.  


So thatll be that.  Powerplant inside a kiln.. 2 birds with one stone.


Thanks guys. 

[tule peak timber]

I live in a camper because im that poor.   Im talking about making something from nothing like i always have.  Its not discouraging, just not any sort of option.

Mike,For what it is worth,when I first met my wife we lived in a borrowed travel trailer parked at the edge of an oil field supply company's lot for years.We used buckets and a hose hung out of a tree for plumbing.
   It is possible to make something out of nothing.
   Your friend on the Forum.......

[alan gage]

What about building a solar collector next to the reefer (empty box with clear panels and painted black inside) and then a fan to blow that air into the reefer?

Alan

[doc henderson]

@GeneWengert-WoodDoc 

[mike_belben]

I live in a camper because im that poor.   Im talking about making something from nothing like i always have.  Its not discouraging, just not any sort of option.

Mike,For what it is worth,when I first met my wife we lived in a borrowed travel trailer parked at the edge of an oil field supply company's lot for years.We used buckets and a hose hung out of a tree for plumbing.
  It is possible to make something out of nothing.
  Your friend on the Forum.......

Good on ya Tule.  I have no complaints.  I could sign my name on a brand new house and re-enter the high pay higher payment rat race but its not worth it to me, BTDT, recipe for misery.
  My kids are still in the trash everything phase, but im the one who has to pay for or fix what they wreck.   let them trash an old camper. When they get mature enough to treat things nice or get out, we will have nicer things.  None of that makes me tick so it can wait.  I got no payments, deed is in the safe and i can tell everyone to pith off.  Thats what i care about. We may not have much but its OURS.  The Lord has been good.  

[mike_belben]

What about building a solar collector next to the reefer (empty box with clear panels and painted black inside) and then a fan to blow that air into the reefer?

Alan

Firewood selling season is short here and when its over thats it for the year. People just dont buy wood in summer where winters are milder.  
  I can make a generator come to life on a rainy night but the sun just doesnt listen to me. 

[alan gage]

What about building a solar collector next to the reefer (empty box with clear panels and painted black inside) and then a fan to blow that air into the reefer?

Alan

Firewood selling season is short here and when its over thats it for the year. People just dont buy wood in summer where winters are milder.  
 I can make a generator come to life on a rainy night but the sun just doesnt listen to me.

Yeah, I hear ya. I know it wouldn't fly up here in the winter, didn't know what it was like in your neck of the woods. I guess mostly I was thinking of something that would let you cheaply dry wood through the summer and then have it ready to sell in the winter.
Alan

[Walnut Beast]

I live in a camper because im that poor.   Im talking about making something from nothing like i always have.  Its not discouraging, just not any sort of option.

Mike,For what it is worth,when I first met my wife we lived in a borrowed travel trailer parked at the edge of an oil field supply company's lot for years.We used buckets and a hose hung out of a tree for plumbing.
  It is possible to make something out of nothing.
  Your friend on the Forum.......

Good on ya Tule.  I have no complaints.  I could sign my name on a brand new house and re-enter the high pay higher payment rat race but its not worth it to me, BTDT, recipe for misery.
 My kids are still in the trash everything phase, but im the one who has to pay for or fix what they wreck.   let them trash an old camper. When they get mature enough to treat things nice or get out, we will have nicer things.  None of that makes me tick so it can wait.  I got no payments, deed is in the safe and i can tell everyone to pith off.  Thats what i care about. We may not have much but its OURS.  The Lord has been good.  

Absolutely. You can make more decisions for yourself instead of them being made for you 😊

[Southside]

I live in a camper because im that poor

Mike - you are not the only one.  Houses don't make you money every month, they are a luxury. My approach was make the land and business buy me a house rather than the other way around.  

[YellowHammer]

A heated and vented kiln, whatever the manner of heating, is an excellent way to get rid of moist air in a kiln, very fast.  

A true direct fire or even indirect fire kiln will dry wet very fast as long as the heat source can keep up with the venting rate.  In many cases, burners use propane and blast heat in to warm heat the chamber.  Venturies are used to control the air flows exiting the kiln, and the more heat in and the hotter the kiln can be maintained by venting air, the more the wood will evolve moisture, and the faster that moisture will be carried outside.    

So using the heat form the engine and the exhaust will provide a good bit of heat, and since one of the byproducts of combustion is water, I would do as you suggest and run the exhaust through a heat exchanger and not introduce it unto the kiln.  I also wouldn't pump the exhaust into the chamber simply for CO safety reasons.

To maintain temperature, a simple self opening temperature controlled vent would work, and make the system pretty hands off.

If you run the generator continuously and can maintain higher temperatures, 120F or even up to 170, while still venting the moist air, you would have a very effective kiln.  You could also scavenge a few watts of power to run some fans to circulate the air in the kiln.