[Gasification] Gasification Digest, Vol 6, Issue 17 Where does room moisture go in the winter time?
Mark Ludlow
mark at ludlow.com
Wed Dec 13 19:11:17 CST 2006
Hi Ron,
Water vapor passes from regions of higher vapor pressure to areas of lower
vapor pressure. Usually the water that evaporates is in liquid form but even
ice will evaporate (sublimate) given the right driving potential (dry winter
air). Dehumidifiers will not collect water that has a dew point below the
temperature of its refrigerant-cooled condenser surfaces. Most air has
excess water absorbing capacity so ventilating your basement with ordinary
air will likely result in a removal of water.
Venting your dryer into your basement is always a bad idea unless you live
in a hot, arid climate. Dryer air is close to being saturated with water (at
its dew point) and it will condense on the first cooler surface it finds,
where it helps to provide a perfect environment for wood rot and mildew. On
the other hand, adding a moderate amount of moisture to very dry
central-heating air raises the apparent comfort level because the enthalpy
(heat value) of moist air is higher than that of dry air.
Mark
-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of Ron Wagner
Sent: Wednesday, December 13, 2006 3:21 PM
To: gasification at listserv.repp.org
Subject: Re: [Gasification] Gasification Digest, Vol 6,Issue 17 Where does
room moisture go in the winter time?
I just dealt with a minor kitchen flood that ended up
in a corner of the basement. I have also been putting
humid dryer air into my basement, rather than vent it
out. I could not collect any water in my dehumidifier!
Fans quickly dried things out. My house was quickly
dry. Where does the H20 go?
Could I dry biomass in my electric dryer? The humidity
dissapears.The heat goes into the house. Maybe I could
dry it in a burlap bag.
Ron Wagner
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> Today's Topics:
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> 1. heat required for drying (Toby Seiler)
> 2. Re: heat required for drying (MMBTUPR at aol.com)
> 3. Re: heat required for drying
> (Rodenhuis, E.J. (Erik Jan, Student TBK))
>
>
>
----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 13 Dec 2006 05:33:22 -0800 (PST)
> From: Toby Seiler <seilertechco at yahoo.com>
> Subject: [Gasification] heat required for drying
> To: gasification at listserv.repp.org
> Message-ID:
> <861580.27485.qm at web38201.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Dear Erik,
>
> I'm probably repeating something that you know.
> It takes just over 1000 btu to turn one pound of
> water (liquid) into vapor (after reaching 212f) and
> in the condensation gives back about 970 btu. Of
> course one pound of water raised one degree is a
> btu., but ambient to 212f is relatively small when
> considering phase change, but not inconsequential.
> Then come issues like the molecular bound water
> versus free water, when dealing with woody material.
> Generally, I believe drying must target a 10 to 16%
> moisture content which is about the end of free
> water and beginning of bound water in wood.
> Calculating the incoming weight of the water content
> in the fuel less the outgoing desired will give the
> weight desired to be removed (as vapor), times the
> 1000 btu/lb (plus ambient to 212f), gives the energy
> required to come out of the process, divided by
> efficiency, for input energy.
>
> One would think that some practical use would
> exist for the energy given up and not just discharge
> to the atmosphere as steam. It takes a lot of
> energy to dry, but the wise was of the energy from
> condensation seems prudent.
>
>
> Regards, Toby Seiler
>
>
>
>
> ---------------------------------
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> ------------------------------
>
> Message: 2
> Date: Wed, 13 Dec 2006 08:53:40 EST
> From: MMBTUPR at aol.com
> Subject: Re: [Gasification] heat required for drying
> To: seilertechco at yahoo.com,
> gasification at listserv.repp.org
> Message-ID: <d2c.1da5f66.32b15fe4 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> to Gasification List from
> Lewis L Smith
>
> Ref the terms "free" versus "molecular bound" water.
>
> I recall from my biomass days that we measured the
> water content of grasses
> by heating a sample of the grass until dry in a
> small oven. This gave us an
> "oven dry" sample which was then weighed. This
> weight was subtracted from that of
> the original material, and the difference was
> divided by the latter to give
> an estimate of the percent H20 in the harvested [or
> sun-dried] grass. Such
> information was of course essential for making
> boiler efficiency calculations and
> for other purposes.
>
> I was told by one of the persons performing these
> tests that the oven only
> extracted the intercellular water, not the
> intracellular water, so the dried
> sample was really only 94% "dry". I eventually came
> to ignore this distinction in
> my calculations as everyone else did, and it made no
> difference of importance
> for our purposes.
>
> Was our intercellular H2O what you call "free"
> water, and our intracellular
> what you call "molecular bound" ?
>
> Cordially. End of message.
>
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 13 Dec 2006 15:54:17 +0100
> From: "Rodenhuis, E.J. \(Erik Jan, Student TBK\)"
> <e.j.rodenhuis at student.utwente.nl>
> Subject: Re: [Gasification] heat required for drying
> To: <MMBTUPR at aol.com>, <seilertechco at yahoo.com>,
> <gasification at listserv.repp.org>
> Message-ID:
>
>
<C655E6719422744297B5910BC105AAD15FBEA1 at EX02.service.utwente.nl>
> Content-Type: text/plain; charset="us-ascii"
>
> Lewis, Toby and list,
>
> True, but as you say it doesn't make a difference
> for our purposes. I
> conducted similar tests on samples, simply dry the
> samples in an oven at
> 110 degrees Celsius until they stop losing weight.
> There is no free
> water anymore in the cellular space, but there is
> still bound water in
> the cell walls.
> Given the ambient temperature and air humidity we
> can calculate the EMC
> (equilibrium moisture content). There is a
> calculator available at
> http://www.woodbin.com/ref/wood/emc.htm
>
> Toby, thanks. I knew this, when formulating it this
> way you have the
> theoretical energy need for drying. As you mention
> correctly the next
> step is attributing an efficiency to the drying
> system used. Same
> question formulated another way.
>
> Erik
>
>
> -----Oorspronkelijk bericht-----
> Van: gasification-bounces at listserv.repp.org
> [mailto:gasification-bounces at listserv.repp.org]
> Namens MMBTUPR at aol.com
> Verzonden: woensdag 13 december 2006 14:54
> Aan: seilertechco at yahoo.com;
> gasification at listserv.repp.org
> Onderwerp: Re: [Gasification] heat required for
> drying
>
> to Gasification List from
> Lewis L Smith
>
> Ref the terms "free" versus "molecular bound" water.
>
> I recall from my biomass days that we measured the
> water content of
> grasses
> by heating a sample of the grass until dry in a
> small oven. This gave us
> an
> "oven dry" sample which was then weighed. This
> weight was subtracted
> from that of
> the original material, and the difference was
> divided by the latter to
> give
> an estimate of the percent H20 in the harvested [or
> sun-dried] grass.
> Such
> information was of course essential for making
> boiler efficiency
>
=== message truncated ===
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