[EnergyPlus_Support] moisture flux in internal walls (make the question more clear)

[habaza11@xxxxxx]

Thank you for your response, and I am sorry because my question was not very clear.
Of course masonry walls have big thermal and moisture storage. However, when simulating an internal wall ,  E-Plus gives four outputs such as

ZN001:WALL004:Inside Surface Mass Flux[kg/s/m2](Hourly) (0.00082582317)ZN001:WALL004:Outside Surface Mass Flux[kg/s/m2](Hourly)( -0.00085717527)

ZN002:WALL004:Inside Surface Mass Flux[kg/s/m2](Hourly)( 0.00076743244)
ZN002:WALL004:Outside Surface Mass Flux[kg/s/m2](Hourly) (-0.00079883036)
Since wall004 is a shared between zone 1 and 2 then
wall004  inside surface in zone 1 is the same wall004 outside surface for zone 2. 
If this is the case why do we have different readings at a certain time( other than the sign convention) 
Thank you again


Linda Lawrie <linda@xxxxxxxxxx> wrote:


Linda Lawrie <linda@xxxxxxxxxx> wrote:

>At 12:22 PM 2/4/02, habaza11@xxxxxx wrote:
>>Sirs;
>>When an internal wall is shared between two zones. I assume that the 
>>external layer of this wall will be the internal layer of the same wall in 
>>the other zone that shares the same wall, and visa versa.
>
>Your assumption is correct once you reach Steady-State (SS) for any given 
>surface for thermal and moisture fluxes.  Since you are using the Moisture 
>Transfer Function (MTF) solution you now have a storage term for both 
>moisture and heat inside the wall.  In many typical cases you will not 
>obtain steady state conditions for a long enough time to reach a constant 
>moisture mass flux rate in a wall; the time constant for moisture transfer 
>can be much longer than for heat flux.  You would have to setup special 
>runs with specified and constant boundary conditions to obtain this type of 
>result, ie. Constant outside temps and moisture, constant heat and moisture 
>loads inside the zones, and constant and non-varying temperature and 
>moisture control profiles varied enough between the 2 experimental zones to 
>force the heat and mass flux in the same direction for a long period of 
>time and then watch the fluxes slowly go to SS.  Given this experimental 
>simulation run you would see both the heat and mass fluxes from inside to 
>outside go to the same value.  In normal simulations you rarely achieve 
>these controlled conditions and would rarely see the fluxes go to SS.  Keep 
>in mind when using the MTF calculation that the thermal flux and 
>temperature profiles also affect the moisture flux and profile, and vice-versa.
>
>The sign convention is the same for both the thermal and moisture fluxes; 
>it is positive into the surface from the outside air and positive from the 
>surface into the zone air.
>
>The sign convention for flux has nothing to do with absorption and 
>desorption, which is the internal storage process for moisture.  Absorption 
>is when the water vapor changes to a liquid in the pore structure in the 
>layer and then releases the heat of vaporization.  Desorption is when the 
>liquid changes to a water vapor in the pore structure in the layer and then 
>requires the heat of vaporization.
>
>(Supplied by Linda Lawrie)
>
>
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