Hops Dryer 2.0

[Naked_Hops]

I started off with an old school locker. I decided to start from scratch and this is what I came up with.

It's 6 feet tall and the trays are 2'x3'

I used an old desk fan. I took off the guard and switched the fan blade. It doesn't move as much air as I thought.

I am going to sheath it with 1/4" plywood and make it as air tight as I can.

The space under the trays is the perfect height for my dehumidifyer.

We'll see what happens. I still don't think I can dry all 50 plants, but we'll see what happens.

I'll take any advice anyone can come up with!

 

[avidhomebrewer]

Looks like a pretty sweet setup. Let us know how it works.

 

[Randar]

Like it. I presume you'll be using ambient air to dry? If you were going to use a blower or fan you'd probably want to close it in.

How many wet lbs of hops do you expect to be able to dry at a time in this set-up?

 

[GVH_Dan]

1. Nope, that fan isn't going to be able to do it. Axial fan's are notorious for not being able to handle much pressure drop. That fan could maybe get through 1/2 that depth.

2. You mentioned the space below is big enough for your dehumidfier. But it looks like you have the fan pushing the air down and through the beds. Why not flip it around, seal the thing up and pull dehumidfied air up and through? then you will get more drying potential on them.

3. Be ready to do the shuffle. With that many trays, the ones exposed to the dryer air will dry much faster than the last. Either they will have to be removed sequentially or you will need to shuffle them around several times.

 

[Naked_Hops]

I took the fan blade off and flipped it in the opposite direction. Any ideas on another fan choice?

I am going to sheath it up with 1/4" plywood later tonight.

I'm ready to spend time rotating trays!

I hope this thing works!

I'll post some more pics after I button it up tonight.

 

[SAMPLER]

Would there be any interest in using a rigid foam to add the to side to create a more controlled temperature to the box. Personally, I was thinking because in the late summer and fall months in Maine we have a pretty quick fluctuation in temp between day and night. Plus I have 4 sheets of 1 inch R7 sitting in my garage.

If built correctly this could double as a fermentation chamber in the summer months.

Two birds one stone :0

 

[Naked_Hops]

I like what you're thinking. Where are you located?

 

[3PegBrew]

1. Nope, that fan isn't going to be able to do it. Axial fan's are notorious for not being able to handle much pressure drop. That fan could maybe get through 1/2 that depth.

2. You mentioned the space below is big enough for your dehumidfier. But it looks like you have the fan pushing the air down and through the beds. Why not flip it around, seal the thing up and pull dehumidfied air up and through? then you will get more drying potential on them.

3. Be ready to do the shuffle. With that many trays, the ones exposed to the dryer air will dry much faster than the last. Either they will have to be removed sequentially or you will need to shuffle them around several times.

First of all PROPS for the design. This looks amazing. I sort of got a hard on from it

Second....I agree that the fan won't work properly.

Third....maybe make two of them so you don't have as many racks to go through?

 

[GVH_Dan]

I took the fan blade off and flipped it in the opposite direction. Any ideas on another fan choice?

Fan selection is a combination of CFM and pressure drop. You need to find a fan that will give you the desired air flow at the pressure drop you are imposing.

I've been doing A LOT of experimenting to try to come up with the pressure drop at various depths of hops, but I have not gone as deep as you are going so I really can't comment. You may want to look into a centrifugal fan, similar to what is found on the high end kitchen ventilation hoods. They are put on those because they are quite, but they will also over come more pressure drop than an axial fan.

 

[GVH_Dan]

Would there be any interest in using a rigid foam to add the to side to create a more controlled temperature to the box.

You'll probably be passing so much air through it, the insulation wouldn't matter.

 

[Naked_Hops]

I don't care about noise. Hell I'd throw an aircraft prop on a gas engine if I thought I could do it without killing myself. I'll see if I can scrounge up a range hood at the dump, or craigslist. I could just make another one like this with the hood on top.

I still don't think I will be able to dry everything I have grown with this beast. I really just have an annoying amount of hops to deal with. Too much to use, and not enough to really sell. I am going to make some larger trays and put some fans on them while the dryer is doing it's thing. I did get slightly more capacity however. I picked up a 4 tray counter-top food deyhdrator for $5 at Goodwill.

 

[SAMPLER]

I like what you're thinking. Where are you located?

South Portland... You?

 

[SAMPLER]

You'll probably be passing so much air through it, the insulation wouldn't matter.

Good point!

 

[GVH_Dan]

I don't care about noise. Hell I'd throw an aircraft prop on a gas engine if I thought I could do it without killing myself. I'll see if I can scrounge up a range hood at the dump, or craigslist. I could just make another one like this with the hood on top.

Yeah, your not installing that type of fan for the noise but to be able to overcome the pressure drop. Look carefully at the fan hood. The cheap ones have axial fans which will do you no better than what you all ready have.

 

[ThreeDogsNE]

Do you know any HVAC guys? An old furnace "squirrel cage" fan should give plenty of CFM of air movement for your purposes, and should tolerate more static pressure. You would have to get a bit more creative about building a housing for it.

 

[rniles]

How much CFM should you have??

 

[ThreeDogsNE]

That depends on the area for your hops, the density, and how much of a hurry you are in. I think density will be your biggest challenge, because furnace blowers and especially window fans are not intended to handle high static pressures. The furnace fan should treat you better here. I think I'd get the biggest furnace blower I come across that I can readily connect to available power, and build for a wide area and shallow density. However, I should admit that I'm not an engineer, and my knowledge in this area comes from dealing with dust collection systems, not food dryers. We have a lot of engineers on this site; will any set me straight?

 

[GVH_Dan]

Pick you CFM based on the area of the hop bed to get you the desired velocity...somewhere around .5 to 1 feet/sec.

The trick is sizing the fan. Air flow from a fan is adjusted based on pressure drop. More pressure drop means less air flow.

Axial fans are awful at this. Take a box fan like you can get for $10. With nothing in front of it, you can get 2,000 to 3,000 CFM. Put a $0.50 filter in front of it and your airflow drops to half. Put three filters and the airflow drops to nothing.

Centrifugal (squirrel cage, scooper, forward inclined, backward inclined, furnace fan, blower, etc.) can over come much more pressure drop and will give you better performance.

On an oast this size, I would be careful with using an old furnace fan. You may end up shaking/fluidizing the hops as they dry. Excessive shaking will drop out the lupulin. You could turn it around and push air down, but give yourself space so it doesn't blast the hops. Or put it in the bottom to pull it through.

 

[Naked_Hops]

I used to have an empire heater that just heated one room. It had a squirrel cage fan in it, but it wasn't super powerful. I'll try to find one of those.

I just picked one bine the other day and used my Goodwill food dehydrator. It took up all 4 trays jam packed. I don't think I have enough room in my 2.0 dryer and my foot locker. I think I'm in over my head.

 

[GVH_Dan]

Just pick what looks the ripest and what you can fit in the drying equipment you have. If you have too much, spread out the dryest hops you have on screens, or a tarp in a shallow layer in the dryest, coolest place you can find and let them sit until you have space available to finish drying them. You'll survive.

 

[Naked_Hops]

I've got the second floor of a barn. It's 16X30. I've been building 3x3 screens on and off. I think I'll get it figured out. I still have no real good way to package this stuff. I've got to talk to the brewer and ask how he wants it delivered. Any ideas?

 

[rniles]

Can anyone estimate what the CFM required would be for a smaller oast that is about 7600 cubic inches (20"x20"x18") ? Three shelves for hops at about 20"x20". One hop depth for each shelf.

 

[GVH_Dan]

CFM, sure. Face area x's your velocity.

You face area is 20" x 20" = 2.78 sq ft

What velocity do you want? If you are pushing up, I don't recommend going over 1 ft/sec = 60 ft/min.

60 ft/min x 2.78 ft^2 = 166.8 CFM

The trick though, fans are rated for CFM at a given pressure drop. If you are going through 18", you should be good with any fan beyond a box fan. If you are going through 3 x's 18"...that's a lot of hops. I would re-think your design.

 

[rniles]

Thanks GVH .. I do appreciate the help.. ...the "oast" is like that pictured but instead of the two shelves shown, I want to make sure the fan will work with three shelves. It's just a 20"W x 20"L x 18"H box with three shelves that are 20" x 20" ...

as far as velocity ...I'll take your recommendations. Without you telling me, I would have no idea what I would want

CFM, sure. Face area x's your velocity.

You face area is 20" x 20" = 2.78 sq ft

What velocity do you want? If you are pushing up, I don't recommend going over 1 ft/sec = 60 ft/min.

60 ft/min x 2.78 ft^2 = 166.8 CFM

The trick though, fans are rated for CFM at a given pressure drop. If you are going through 18", you should be good with any fan beyond a box fan. If you are going through 3 x's 18"...that's a lot of hops. I would re-think your design.

 

[GVH_Dan]

So 18" would be the theoretical maximum, right? In reality, each tray will probably hold...3 inches of hops? So 9 inches all total?

Velocity, CFM, pressure drop are all inter-related when it comes to fans. You pick a fan for a given situation, but any change to 1 affects all three in ways that affect all three.

If I were you and wanted to get away with the least expensive method of moving air, I would start by getting a simple 20 x 20 (or slightly smaller) box fan. Cheap is fine. Those usually move 2000 to 3000 cfm at 0 pressure drop, but they drop off rapidly. I would guess that with 3 to 9 inches of hops, that would drop to 600 cfm or less quite rapidly, which gets you in the correct area.

I would also suggest you mount it on the bottom sucking air from the top down through them. What you don't want is hops that are floating when dry because this will shake the luplin out. By pulling down, it keeps that from happening plus you get a bit better uniformity across the hops bed.

Once you have it hooked up and pulling, feel the inlet at top and make sure you can feel some airflow. If you can barely feel the air moving, you may want to turn the fan around to get more drying potential on them.

Also, rotate the shelves occasionally to get uniform drying between shelves.

 

[rniles]

Yeah ..the 18" would be the air space ...each shelf most likely would only have 1 inch of hops ..unless things went exceedingly well that year then I guess they could hold 3"s.

.. so you're thinking for that space, about 600 CFM is what I should be shooting for?

 

[GVH_Dan]

Probably less. The number I came up with before was only 167 CFM. Most box fans do a lot more than that, but without pushing through anything. If you are at about 3 inches of hops, it will slow that velocity down, but just to be sure, make the air flow down through the hops so they aren't bouncing around when they are almost dry.

 

[rniles]

Thank you - appreciate the info!

 

[SAMPLER]

I would also suggest you mount it on the bottom sucking air from the top down through them. What you don't want is hops that are floating when dry because this will shake the luplin out. By pulling down, it keeps that from happening plus you get a bit better uniformity across the hops bed.

Could you mount the fan above and push down into the bed of hops. This would press them into screen and keep them more in place rather than blowing around and most likely increase penetration through the hop layers?

 

[GVH_Dan]

Whether the fan is pushing air down (from top) or pulling air down (from the bottom) the air is still going top to bottom at the same average velocity. Note, I said "average". As air is pushed out of a fan it isn't uniform. There's something called "fan affects" that influences the air profile. in other words, it is higher in some areas and lower in others. But on the suction side, it is more uniform. So sucking the air through will give a more uniform profile than pushing it through.

 

[SAMPLER]

Whether the fan is pushing air down (from top) or pulling air down (from the bottom) the air is still going top to bottom at the same average velocity. Note, I said "average". As air is pushed out of a fan it isn't uniform. There's something called "fan affects" that influences the air profile. in other words, it is higher in some areas and lower in others. But on the suction side, it is more uniform. So sucking the air through will give a more uniform profile than pushing it through.

Sounds pretty simple. I guess I'll have to do some further planning for next season. I'll keep an eye open for some sort of exhaust fan. Thanks for the clarification