[TRNSYS-users] Massless Layer

[adnan rasheed via TRNSYS-users]

Hi camila,

i am not sure about this fully may be any senior person here can guide you
better. i just want to share my experience with u. TRNSYS actually
calculate heat transfer coefficient during simulation after every time
interval on the basis of the material's properties, does not use constant
value during whole simulation period. its value is dependent on outside and
inside of building weather conditions. external and internal convective
heat transfer coefficient( that are  input values). my suggestion is to
ignore and try to validate your computed and experimental results by
comparing. in my case i confirm overall heat transfer coefficient manually
by using following equation..

 U-value (overall heat transfer coefficient) = Q/ A(Ti - To)

Q is heat losses through the wall you want to check( select form layer
output in TRNBuild), A area of the wall, Ti and To inside and outside
temperatures. so u can calculate U-value for each time period. hope this
will work.

Please let me know if you get some other information about this.

Regards

adnan

On Wed, Jan 18, 2017 at 8:40 AM, Camila Davila Valdebenito via TRNSYS-users
<trnsys-users at lists.onebuilding.org> wrote:

> Hi TRNSYS users!
> I'm simulating a building and I need to create a massless layer. I've
> calculate the overall heat transfer coefficient that I need for some "X"
> wall (6.6581 W/m2K in this case). The massless layer requires a thermal
> resistance in [hm2K/kJ], which is the reciprocal of the heat transfer
> coefficient. Doing this, I get R=0.0417203 [m2Kh/kJ].
> When I create a wall with this layer (and this R value) the wall type
> manager shows me an U value of 3.123 [W/m2K] (totaly diferent of the one
> that I need).
> Does anyone knows how TRNSYS calculate this? or what is the right unit
> conversion?
> Thanks for your time
>
>
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