Dear all,
(Thanks David for your answer..)
I have furthermore investigated this issue and I have found the following example proposed in the TRNSYS mailing list some years ago.
I have now another question concerning how to get the “k = gradient of sorptive isothermal line”. In the TRNSYS type56 manual there is a table of “material data for buffer storage humidity model”, but there are no references concerning the sources and/or the calculation conditions.
As “k” is not constant (at least over the 0%-100% RH range as it strongly varies with RH itself), which are the conditions at which the reported TRNSYS “k” refer?
Thanks for helping and supporting,
All the best
Stefano
- Date: Fri, 12 Jul 2002 01:17:49 -0500
- From: "Matthias Rudolph" <rudolph@xxxxxxxxxxxxxx>
- Subject: Re: AW: humidity calculation
I think it is not that easy to define the absolutely correct value for the
humidity capacity ratio of
the Capacitance humidity model[...]
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
From: David BRADLEY [mailto:d.bradley@tess-inc.com]
Sent: venerdì 2 settembre 2011 16.37
To: Avesani Stefano
Cc: trnsys-users@cae.wisc.edu
Subject: Re: [TRNSYS-users] multiplication factor and effective moisture capacitance estimation
Stefano,
I have looked a bit in the literature and have seen that values between 5 and 15 are typical. Completely unscientifically, I usually use 10 for a "typical" room. I would use a higher value if I were dealing with a room that had a lot of furnishings or a lot of papers. I typically use a value of 5 for corridors and lobbies since they tend to be less heavily furnished.
Best,
david
On 9/1/2011 10:58, Avesani Stefano wrote:
Dear all,
I am wondering how to estimate the “humidity capacitance ratio” - = multiplication factor generally in the range of 1 to 10 – needed using the simplified (effective capacitance humidity model) type56 moisture model.
Any suggestion, experience, literature references?
I have looked in the manual but I could not find any clue!
Thanks a lot!
All the best
Stefano
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