RE: [EnergyPlus_Support] Space humidity fluctuation

[Christian Struck <Christian.Struck@xxxxxxxxxxxxxxx>]

Mike,

many thanks! 
In my case you brought light into the dark!

Kind Regards

Christian



> -----Original Message-----
> From:	Michael J. Witte [SMTP:mjwitte@xxxxxxxx]
> Sent:	11 February 2003 22:36
> To:	EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject:	Re: [EnergyPlus_Support] Space humidity fluctuation
> 
> Christian:
> 
> For your application, the MTF is best applied to the paper as 
> internal mass and not the envelope.  The interior of the room would 
> stay at much more constant temperature and humidity ratio conditions 
> and thus extend the time that the material properties would be in 
> range.  Be sure to read the section on Moisture Transfer Material 
> Properties in the Engineering Document, starting on p. 23.
> 
> Also, remember that MTF models moisture transfer through the envelope 
> as well as moisture capacitance.  This may explain why adding the 
> envelope MTFs caused the conditions to change more rapidly.
> 
> Another option is to use the EMPD simulation on the internal mass and 
> the building envelope.  The EMPD solution only models moisture 
> capacitance, no moisture transfer through the envelope.
> 
> Regarding the results with MTF vs. CTF, remember that the absorption 
> or release of moisture in the surfaces will alter the heat transfer 
> at the surfaces.
> 
> Mike
> 
> 
> 
> 
> On 7 Feb 2003, at 17:51, Christian Struck wrote:
> 
> > Linda,
> > 
> > many thanks for your quick reply to the simulation output! 
> > 
> > My question now is a of different nature. 
> > I use the MTF algorithm to evaluate the influence of paper materials
> > on the room humidity after plant failure. The space contains shelves
> > filled with tons of paper. I used the internal mass facility to define
> > the papers surface area and properties. I also applied MTF properties
> > to the building fabric since I taught it is necessary to follow the
> > MTF approach throughout the model.
> > 
> > When comparing results for a model with MTF properties applied to the
> > paper only and a model with MTF properties applied to paper and
> > building fabric I noticed the environment is more stable for the paper
> > only option. Could you please advice whether it is necessary to apply
> > MTF properties to the building fabric and I how does the MTF
> > formulation treats the building fabric in case no MTF properties were
> > applied. 
> > 
> > Another issue I noticed is, when comparing MTF and CTF results for the
> > 24h plant failure the resulting mean air temperatures in the space
> > decrease using CTF and increase using MTF independent on the external
> > temperature. I do not have an explanation for that behaviour!  Please
> > provide me with some keypoints I can use to get my understanding up to
> > speed.
> > 
> > many thanks!
> > 
> > Christian
> > 
> > 
> > 
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