Hot air furnace

[Logsnstuff]

Looking at the Talbotts 150kw and lasco 400kw biomass furnaces for drying logs and maybe some boards off the mill, anyone want to put their tuppence worth in? Whether the put out enough heat to dry in the polytunnel or if I need to buy in some containers

[bilke_user]

Surely the heat loss from the tunnels would make it a non starter............am I missing something though?

 

[Logsnstuff]

1 hour ago, bilke_user said:

Surely the heat loss from the tunnels would make it a non starter............am I missing something though?

 

With the airflow from the fans and trying to just dry the centre 4 rows I’m wondering whether it would work same as the drying floors, I’m not after 6 days Drying I have plenty waste I can use so 4,5,6 weeks I have enough to get me to Christmas I’m just going to be short the other side.

[daveatdave]

try taking one of the center stacks out to give more air space around them it should help dry better 

[Chalgravesteve]

On 15/10/2019 at 21:15, Logsnstuff said:

With the airflow from the fans and trying to just dry the centre 4 rows I’m wondering whether it would work same as the drying floors, I’m not after 6 days Drying I have plenty waste I can use so 4,5,6 weeks I have enough to get me to Christmas I’m just going to be short the other side.

The principle of drying wood in a kiln is not necessarily all about heat. The description of "kiln" does tend to make people envisage oven like temperatures, when in fact the way that they work with log drying is the movement of hot/warm air over/past something that holds moisture. Warm air can carry greater amounts of moisture than cold air, so by making warm air flow past moisture laden logs, the moisture can be released from the log and absorbed by the air as it passes by.

 

I have a 40'ft shipping container kiln. For the first two years we just let the heat exchangers blow into the container and it worked ok. But we would struggle to get the temperature inside the kiln much above 28/30 degrees C. So we insulated the walls and ceiling of the kiln with KIngspan insulated boards, and the temperature now sits much higher at the 36 degree+ levels. As a result, we dry the logs faster and better, whilst still using the same amount of energy.

 

So my critique of what you are trying to do, is that when you introduce artificial heat, it will easily escape through the poly tunnel roof, as the heat will rise in the first place. You will also need bloody big fans to move air through that space! So, what works in your favour in the summer, the "greenhouse effect" of the poly tunnel in increasing the temperature of the air inside the poly tunnel works against you in the cooler times as it can't hold onto it.

 

I think you would be better creating a smaller area or areas within the tunnel, so a tunnel (made of ply?) within the tunnel which you can insulate and contain the heat , so that you can dry some stuff in say 2 weeks. You have the heat/fans down one end and removable far end, so you can slow the passage of air and dry what in there. When its dry, open the far end and move the dry stuff out and put new stuff in.

 

As with all this stuff, its all heavy! I'm, not sure how easily you can move a machine and stock around in the polytunnel? You only have to get it wrong once and you have wrecked your polytunnel!    

 

So personally, I think you would be better creating a smaller drying area where you can control the heat and airflow better. I think you will do a lot of work for minimal impact in the polytunnel alone.

 

Creating a drying floor in there would be better, as you would be pushing warm air under the logs to be dried and then it will release upwards through the logs which might work. That warm moist air will hit the underside of the polytunnel and turn into condensation so you need a means of getting the moist air out of the tunnel 

 

  

Edited October 22, 2019 by Chalgravesteve

[Logsnstuff]

1 hour ago, Chalgravesteve said:

The principle of drying wood in a kiln is not necessarily all about heat. The description of "kiln" does tend to make people envisage oven like temperatures, when in fact the way that they work with log drying is the movement of hot/warm air over/past something that holds moisture. Warm air can carry greater amounts of moisture than cold air, so by making warm air flow past moisture laden logs, the moisture can be released from the log and absorbed by the air as it passes by.

 

I have a 40'ft shipping container kiln. For the first two years we just let the heat exchangers blow into the container and it worked ok. But we would struggle to get the temperature inside the kiln much above 28/30 degrees C. So we insulated the walls and ceiling of the kiln with KIngspan insulated boards, and the temperature now sits much higher at the 36 degree+ levels. As a result, we dry the logs faster and better, whilst still using the same amount of energy.

 

So my critique of what you are trying to do, is that when you introduce artificial heat, it will easily escape through the poly tunnel roof, as the heat will rise in the first place. You will also need bloody big fans to move air through that space! So, what works in your favour in the summer, the "greenhouse effect" of the poly tunnel in increasing the temperature of the air inside the poly tunnel works against you in the cooler times as it can't hold onto it.

 

I think you would be better creating a smaller area or areas within the tunnel, so a tunnel (made of ply?) within the tunnel which you can insulate and contain the heat , so that you can dry some stuff in say 2 weeks. You have the heat/fans down one end and removable far end, so you can slow the passage of air and dry what in there. When its dry, open the far end and move the dry stuff out and put new stuff in.

 

As with all this stuff, its all heavy! I'm, not sure how easily you can move a machine and stock around in the polytunnel? You only have to get it wrong once and you have wrecked your polytunnel!    

 

So personally, I think you would be better creating a smaller drying area where you can control the heat and airflow better. I think you will do a lot of work for minimal impact in the polytunnel alone.

 

Creating a drying floor in there would be better, as you would be pushing warm air under the logs to be dried and then it will release upwards through the logs which might work. That warm moist air will hit the underside of the polytunnel and turn into condensation so you need a means of getting the moist air out of the tunnel 

 

  

Thanks for the input, the intention is to leave 1 bag out on the base to create a channel for the hot air so it dries like a drying floor and dry it in sections 4 bags wide and 4 or 5 deep, I’ll be selling from the far end which got what little summer we had so I’m working my way to the back, I’ve found a few 1m (36k m3 an hr) axial fans online which should be enough to blow the condensation out the end and I’m looking to use Something like the yellow flexible hose that can be easily moved around. I thought about the vinyl tarps laid on top to hold the heat a bit but decided that might just create mouldy logs.

[Chalgravesteve]

7 hours ago, Logsnstuff said:

Thanks for the input, the intention is to leave 1 bag out on the base to create a channel for the hot air so it dries like a drying floor and dry it in sections 4 bags wide and 4 or 5 deep, I’ll be selling from the far end which got what little summer we had so I’m working my way to the back, I’ve found a few 1m (36k m3 an hr) axial fans online which should be enough to blow the condensation out the end and I’m looking to use Something like the yellow flexible hose that can be easily moved around. I thought about the vinyl tarps laid on top to hold the heat a bit but decided that might just create mouldy logs.

Yes if you can get it to work as a drying floor, getting the air under the bottom pallets so it can rise through the stacks you might have a chance with that. I’m not sure you can easily push enough hot air in enough volume underneath though without s network of pipes in the pallets? 

[fonzy]

On 15/10/2019 at 21:15, Logsnstuff said:

With the airflow from the fans and trying to just dry the centre 4 rows I’m wondering whether it would work same as the drying floors, I’m not after 6 days Drying I have plenty waste I can use so 4,5,6 weeks I have enough to get me to Christmas I’m just going to be short the other side.

What width is your poly tunnel?

 

Thanks

[Logsnstuff]

On 28/10/2019 at 16:09, fonzy said:

What width is your poly tunnel?

 

Thanks

30’ x 90’ with meter extensions for extra height.