# [EnergyPlus_Support] RE: MTF: output variable meaning & few more doubts.

Thank you for your fast answer, but  I think that the variable "Layer Rel
Humidity" should be expressed in % (per hundred instead of per one). The
other relative humidity variables like "Environment:Outdoor Relative
Humidity" and "Zone Air Relative Humidity" are expressed in units per
hundred. This is not very important but as far as I know it isn't said
anywhere in the manuals. But I have a few more doubts:

- I have made several simulations under winter conditions, and I always get
0% relative humidity in Layer 2. The same problem occurs in
"MTFTermReheat.idf" example under a winter design day (Dry Temp: 5ºC and Wet
Temp: 3ºC). I think that this is not correct, but I don't know what am I
doing wrong.

- In my model I use a Unit Heater to maintain a 20ºC indoor constant
temperature, but although there is no moisture source or sink, the humidity
rate inside is lower than outside (Environment:Outdoor Humidity Ratio: 0.039
kgWater/kgAir and Zone Air Humidity Ratio: 0.034 kgWater/kgAir). I don't
understand the reason for this difference. If I run this model with the CTF
algorithm both variables are the same. Anyway, I was expecting a Zone Air
Humidity Ratio about 0.043 kgWater/kgAir (inside air is coming from the
outside through infiltration, so it should have the same humidity ratio
increased by the difference in the air densities). The vapor pressures for
this conditions will imply a moisture flux from the outside to the inside,
so how is possible to have a moisture inside lower rate if moisture is
coming from the outside through the wall?

- About the "Outside/Inside Surface Mass Flux[kg/s/m2]" variables, I would
like to know the meaning of the sign. I am also surprised about their
magnitude. I am getting values around  -0.00015 kg/s/m2 for the inside
surface mass flux. I think it is a very big value, my wall is 30
m2: -0.00015 kg/s/m2 x 30 m2 x 3600 s/hour = 16.2 kgs of water per
hour?!?!?!?!? You can get a similar value in the "MTFTermReheat.idf" example
with a winter day.

Miguel Angel Pascual

-----Mensaje original-----
De: Richard J. Liesen [mailto:rliesen@xxxxxxxx]
Enviado el: miércoles, 02 de julio de 2003 15:34
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx
Asunto: Re: [EnergyPlus_Support] MTF: output variable meaning

>Can anybody explain me the meaning of the output variables:
>
>- Layer Rel Humidity[]. Units?

This is the Relative Humidity inside the construction at each layer
interface.  Relative Humidity is explained in just about every
Thermodynamic text book, ASHRAE Handbook of fundamentals, and any
Psychrometric book.  It is unitless and runs normally between 0 and 1,
where anything greater than 1.0 there would be condensation.  This value
can be reported along with the humidity ratio to help the user determine
if
there was or could be condensation in the wall construction.

>- Outside Surface Mass Flux[kg/s/m2].

The Surface Mass Flux would be the amount [kg] of moisture that would
enter
or leave that material at the outside face.

Thanks Richard Liesen

>
>
>Miguel Ángel Pascual
>Dtor. Ingeniería
>MIYABI
>mapascual@xxxxxxxxxxxx
>948 203 644
>
>
>
>[Non-text portions of this message have been removed]
>
>
>
>To unsubscribe from this group, send an email to:
>EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
>
>The primary EnergyPlus web site is found at:
>http://www.energyplus.gov
>
>The group web site is:
>http://groups.yahoo.com/group/EnergyPlus_Support/
>
>Attachments are not allowed -- please post any files to the appropriate
>folder in the Files are of the Support Web Site.
>
>
>
>
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate
folder in the Files are of the Support Web Site.

[Non-text portions of this message have been removed]

http://us.click.yahoo.com/Lj3uPC/Me7FAA/ySSFAA/dkFolB/TM
---------------------------------------------------------------------~->

To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files are of the Support Web Site.

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/