Re: AW: humidity calculation

["Matthias Rudolph" <rudolph@xxxxxxxxxxxxxx>]

Dear Mr. Kouba, Mr. Himmler,

I think it is not that easy to define the absolutely correct value for the
humidity capacity ratio of
the Capacitance humidity model. The difficulty is comparable to the definition
of the thermal
capacitance of a zone in Type56. Assuming an office than what depth of the
furniture and the utilities
can be declared as accountable thermal capacity? Basically at least the
capacity of the air volume has
to be accounted for. Probably the right trend for a standard office is to
multiply the capacity of air
by 2 or 3 to take into account the thermal mass of the furniture.

The default value for the humidity capacity ratio of the simple model should be
1
because this represents only the capacity of the air. The default values range
are 1-10 for a standard office because this depends on things like the quality
of the surface of walls. This could be the quality of a layer but also of a
color.

Maybe if you just take into account the surfaces of walls with a low diffusion
Resistance than
one rough way to estimate the humidity capacity ratio is e.g. for a room 5 m x
4 m x 3 m:

The mass of water in the air and the mass of water in walls, if all walls and
the ceiling have 0.005 m thickness of  gypsum. The Diffusion Resistance mü of
those walls is assumed to be low.

Material          roh [kg/m³]     kapa [kgH2O/kgmat/relhum]         mü
Gipsum                900               0.015                        8

m water air     = 60m³     * 1.2 kg_air/m³     * 0.016 kg_H20/kg_air = 1.15
kg_H2o
m water walls   = 0.37m³   * 900 kg_mat/m³     * 0.015 kg_H20/kg_mat = 5.0
kg_H2o

this would result in a Ratio =(mw_air+mw_wall)/mw_air= 5.3


kind regards,

Matthias Rudolph




Robert Kouba wrote:

> Unfortunatly not yet....
> Regards
> Robert Kouba
>
> At 10:00 02.07.02 +0200, you wrote:
> >Dear Mr. Kouba,
> >
> >some time ago you have sent a question about the humidity calculation with
> >TRNSYS. Since I work at a similar problem I would like to know if you have
> >received an answers.
> >
> >Thanks in advance
> >
> >Robert Himmler
> >
> >
> >*************************************************************
> >
> >Steinbeis-Transferzentrum Energie-, Gebaude- und Solartechnik
> >TU Braunschweig - Institut fur Gebaude- und Solartechnik
> >Dipl.-Ing. Robert Himmler
> >Kopenickerstr. 48 - 49 (im DAZ)
> >10179 Berlin
> >
> >Tel 030/278789-31
> >Fax 030/278789-60
> >
> > > -----Ursprungliche Nachricht-----
> > > Von: owner-trnsys@relay.doit.wisc.edu
> > > [mailto:owner-trnsys@relay.doit.wisc.edu]Im Auftrag von Robert Kouba
> > > Gesendet: Freitag, 29. Marz 2002 14:43
> > > An: trnsys@relay.doit.wisc.edu
> > > Betreff: hunidity calculation
> > >
> > >
> > > Dear collegues,
> > >
> > > I am trying to include a humidity calculation in the simulation for an
> > > office building utilizing
> > > the simple humidity model provided within TYPE56. To do this I
> > > have to choose
> > > an effective mass ratio M_eff/M_air which according to the
> > > handbook should
> > > be chosen
> > > between 1 and 10. Does anyone have any experience in choosing this
> > > parameter and in particular how to
> > > roughly relate it to the actual building set-up (plants,
> > > furniture, etc...).
> > >
> > > Thanks in advance and regards
> > > Robert Kouba
> > >
> > >
> > > Robert Kouba
> > > Institute for thermal engineering
> > > Div. Solar Energy and
> > > Thermal Building Simulation
> > >
> > > Graz University of Technology
> > > Inffeldgasse 25/B
> > > A.-8010 Graz, Austria
> > > Tel: +43(0)316 873-7314 or 7306
> > >

--


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 Matthias Rudolph
 TRANSSOLAR Energietechnik GmbH
 Curiestrasse 2
 70563 Stuttgart
 Germany

 phone: ++49-711-67976-192
 fax:     ++49-711-67976- 11

 Mailto:rudolph@transsolar.com
 http://www.transsolar.com
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