Will you change??

[agchat]

Now to add my two cents, after all I did start this thread, I always monitor the humidity, no matter if we are cooling or drying. If th RH is over 85% by 11 or midnight, the fans get turned off. I just do not seeing especially over 90 RH being sucked into a bin for more than 8 or 9 hours. Maybe I am totally wrong.

[bluefargo]

The gentleman was interviewed on CBC Radio at noon today. I listened very intently. You bet I'll change the way I do things. We have been guessing all these years. Finally someone actually did some research, It is counter intuative but made good sense. Ignore these results at you peril!

[Tucker]

I think the gist of the article is the idea that cool night air with high RH still
carries less water into your grain than hot daytime air with lower RH. Plugging
average Regina mid-September values for temp and humidity into a psychrometric
calculator seems to support this theory.

Daytime air at 20 degrees C and 40% RH will hold 5.898Kg of water per 1000Kg dry
air. Night time air at 6 degrees C and 85% RH holds a little less at 5.004Kg per
1000Kg dry air.

I think that this just shows that night time humidity isn't that bad so it's okay
to run your fans 24 hours. That being said however, 30 degrees C and 50% RH air
holds 13.551Kg of water per 1000 Kg dry air. You might want to stop the fans
during a hot, humid day.

[fjlip]

And a dryer works how? 25C and 30%RH air heated to 180F sure works.
Try it without the heat.
I always thought raising temp lowers RH.

In the interview did he explain the hot air cold grain statement?

[Tucker]

Using your example of 25 degree air at 30%
RH heated to 82 degrees C, that air will
now have a RH of only 1.85%. The water
content of your air didn't change but the
extra heat added a huge amount of water
carrying capacity to it. It's now
(relatively) dry as a popcorn fart and
capable of carrying tons of water out of
your grain as it's pushed through.

[agchat]

"The moisture carried in that hot air collides with the cold grain and is released into the grain."
I do think that alot of this study has a way to many factors involved. The quote from the article is something that is the key factor. Sure if you take grain at 18% moisture and lets say a temp of the grain being 20 celsuis. Now take grain harvested at 18% moisture, if it is a hot day, lets say 30 C, we all know that grain will at least be, if its sunny, 35-36C.
Then why would you not turn your fan on right away? Outside temp during sunny days are always cooler than grain temps till evening.

[Hopperbin]

That Palmer got some seriously flawed shit going on there, I don't care how many degrees he's got he wrong. What does he hope to do by telling us that crap? We all know you cannot dry at night when the humidity is up. Cooling the bin down with night air only is not going to speed up the drying or take more moisture out of the grain. He goes on to say that adding heat to the air will not help drying. I am sure Dry Air should be turning over in their graves with this news as they have studies that show the best way to dry grain is with heat. This guy goes on to say that they put 20 percent moisture grain in a bin and dried it with night air, no way in hell. I can see some moisture coming out of the grain as the grain temp drops but no way in hell will you will dry 18 percent moisture grain with night air, every grain farmer knows that.

[TOM4CWB]

This is a matter of cooling the grain.

If the night temp is 8C... cooling the grain at 25C... the air increases to 25C in the grain and bin...and has extemely low RH because the GRAIN heated up the air. Our Fans are on all day/24hrs once we start cooling grain. Once down to 10-12C... the moisture drops one point just on the 25C to 10C grain temp change... plus the storability on 10C grain is 10 times longer than at 30-35C as it will be at the top of the bin on a full bin/hot day.

[fjlip]

Tucker, that is what I always thought, "water carrying capacity".
Therefore cooler humid air removes zip from your grain, it has less capacity.

Maybe he is talking about DRY cold air, like all winter? Never tried that.

[Tucker]

fjlip, I think Tom is closer to correct on this matter. Cooling the grain
down to safer storage temps is how aeration helps with grain storage the
most. Grain will have to give up moisture as it's cooled just because as it
cools, the RH of the air surrounding the kernels in the bin has to rise.
Any time you can push air into a bin that has lower RH than the air in it,
you're doing some amount of drying with the air exchange. Once the grain is
cooled to the ambient night time temps, blowing more air through it is
probably just wasting energy.

Any supplemental heat you can give the air that doesn't also raise the
water content of it is going to lower the RH of that air and speed drying.

[grrrr]

I am rigging up a system that will bring cold night air into my wifes clothes dryer. The plan is to dry everything with cold outside air Monday night. I can hardly wait to jump into my jeans Tuesday morning, straight out of the dryer!!!!!!!!!!!!

[Hopperbin]

Yep looks like us farmers have done many experiments threw the years. I remember waking up in the morning many times to a blinding fog, go running out to turn the fans off and wonder well how long and how much h2o did I just add to them bins???? Upon unloading it was a lot I just don't have numbers. Raining outside is better than the fog cause fog gets sucked in more than rain and I ain't going to run fans in the rain. Pami has done airation experiments also so could ask them. August if of course typically much better than sept.
Tom I like you like to cool the grain down for winter, spring is a good time to dry grain with air but then again this guy says you take moisture out of the grain better when it is cooling. So then why do us farmers with a lot of experience know that we can air a dry our grain in the spring effictiently.

[Hopperbin]

When you said wife's cloths dryer I thought you said all the wife's cloths.
Then she can come back to bed for some warming up.

[farmaholic]

I think it is fair to say that grain will release alot of moisture during the initial cooling period.
The article states that air(volume not stated) at a temperature of 27*C at and 0%(assumed) RH holds 4.3 kg of water and at 50% RH holds half as much at 2.15 kg. Therefore, it is fair to say that it is half full and can take on more water if conditions are favorable to do so. As RH drops, regardless of temp, shouldn't the air be able to hold more water, since it isn't as full? If RH drops to 30% the air should be able to absorb alot of water, up to the point an equilibrium is reached and the air is no longer able to hold any more water and net drying is no longer occuring(or rate of drying reduced).
What the article doesn't tell us is how much water does cool air hold at about 10*C and 80% RH vs 40% RH(use what ever numbers you want, the important thing here is there is no mention of it). Or is it that air temp doesn't mean as much as %RH. Does air at 30% RH hold the same amount of water at 27*C and 10*C?
Then there is "dew point", which means, at what temp does the air have to cool down to, at a given %RH, for the water vapor in the air to cool and cause condensation. And why would you run fans when the temp is near the dew point.
What about static pressure? Does a high static pressure reduce the airs ability to hold water? Does it in effect squeeze it and reduce its carrying capacity? Or isn't it high enough to make any difference?
I was told to run the fans continuously because the "drying front" continues to move and "rewetting" of the grain happens slowly. The grains we've dried in aeration usually are over dry at the bottom and not dry at the top and near right in the middle. So how long would you have to run the fans to re-wet the bottom to the allowed moisture content?
Can someone who understands this explain it because it seems completely contadictory to what we've been doing!!

[Hopperbin]

Farmaholic lets go with what we know. At harvest time when temps are 30 our grain going in the bin can be upwards of 40. so yes some drying can occure on cool down, hot air dryers work on putting heated dry air into the grain and then also the grain drys uppon cool down. That is a fact. Cool down in a grain dryer is only 1 to 2 hours max. Could be longer but there is no point. And typically when grain is 40 degrees going into the bin then night time temps are also warmer but no one is going to dry grain down better than running the fan all day. That we know.