Dehumidifier vs venting.

[matelot]

Surely a dehumidifier would be the way to go? It would dry out the air so that the dry/ hot air would dry out the logs?

 

We've all seen the condensation on a cold can of coke on a hot day. A dehumidifier would do something similar in your store.

 

imho venting would be foolish as you are losing the hot air (unless you have a heat exchanger or similar).

[openspaceman]

My (amateur) experience suggests that wood loses the first lot of moisture pretty quickly, so long as there's enough ventilation and without needing that much heat. If that's correct, it might be better to use a lot of ventilation at low temperature until the wood's down to 30% or so.

 

 

I agree all the time the ambient RH is low, the thing is as temperature goes down the air's carrying capacity for water goes down and it's ability to carry enough heat to evaporate water goes down too, heat tends to be cheaper than fan power.

 

A dehumidifier is in an essentially closed system (only water leaves) so heat can be conserved in the system, plus all the electricity used ends up in the system as heat.

 

I still haven't run my domestic dehumidifier on a meter to see exactly how much water it produces per kWh but I'm confident a heat exchanger can keep heat in the system plus make use of any unsaturated potential in ambient air for the same air movement.

[aesmith]

Some real figures are given here Cheapest Dehumidifier to Run: The Guide - MeacoMeaco

 

They don't account for latent heat though, so that actual heat added to the space will be greater than the energy consumption. Data from Calorex (http://www.calorex.com/ee_pdf/Dehumidifiers_v4.pdf) gives some examples, suggesting around 50% more.

 

However I still feel that initial drying without heat is the way to go, even air at near to 100% RH will still dry wood to round about 30% if there's enough airflow. So what I'd do is stuff it into the kiln only after doing that first drying, and use the kiln to get it down to whatever you're aiming for, using the dehumidifier.

 

What sort of dehumidifier is it?

[TTS North]

I did use an industrial dehumidifier a few months ago or it was supposed to take 20 litres out every 24 hours but it was nearer 10 over that period. Assuming 65 per cent moisture in a m3 I'd need to remove 450 litres which would take 45 days - that is at ambient temperature with a running cost of say £60.00 for that period. If I add heat to the equation let's say at 10 pence per kilowatt and used a 2kW heater that of course is going to drive up the cost. Question is how much quicker would the moisture be lost if I did add heat - I am sure there will be a sweet spot where the cost of production becomes less than the final value. But I'm struggling to figure out where it would be. If you managed to drive the heat waaaay up e.g. above boiling point - could you reduce the time to a few days I wonder?

 

Good input from everyone BTW.

[aesmith]

I did use an industrial dehumidifier a few months ago or it was supposed to take 20 litres out every 24 hours but it was nearer 10 over that period.

A lot of manufacturers quote water collection at unrealistic temp/RH combinations, I've seen some where they quote at 80%/30Deg C.

[aesmith]

By the way, this calculator shows what I was referring to earlier - even at near to 100% RH wood will dry down to around 30% if there's enough airflow. What it doesn't say is how quickly that will happen. There may be some data on that for people drying for timber, although they'll normally have the end-grain sealed and specifically don't want to dry too fast. Wood Equilibrium Moisture Content Table And Calculator

[TTS North]

I am talking to one of the guys from EBAC/EIPL and they are suggesting something like

 

EIP - CD100 Industrial Dehumidifier.

 

But I don't know if second hand units would work just as well I'm afraid I am coming to the Dehumidifier game rather late.

[matelot]

If you just fancy a "play about" at this stage why not just put a block of ice into a bucket and put it in your store? See how much water condenses inside the bucket.

 

Or put an old freezer in your store and leave the door open? A dehumidifier is basically just a fridge that blows wet air over cooling coils.

[beachbum73]

This may be a costly or not experiment! but i have solar domestic hot water panels which when set up i plan to dry my wood with using a coil of the piping to redirect underneath my woodstacks, heat from the coils can reach some incredible temperatures, with this and the air moving round i expect it to be almost cost free in the summer and winter. Just top and some vented side covers to prevent rain entering but free flow of air. if you can get a hold of these DSHW panels (i got mine for £90) plus the antifreeze/coolant liquid and piping, pump this may be a cost effective way to dry your wood stacks! Just a thought.

[TTS North]

beachbum - is this the sort of thing you're using?

 

[ame]

[/ame]