[TRNSYS-users] R 1347: Time-base, high insulation and high thermal mass combined with floor heating

[David BRADLEY]

Noortje,

   The time base has to do with how often the wall transfer functions 
are updated. The time base is distinct from the simulation time step and 
while it is ideal to have the time base and the time step be equal, it 
is rarely possible. Ventilation and occupancy changes occur as a 
function of the simulation time step. You'll see some stepwise behavior 
in the room air temperature if your time step and time base are 
different but in my experience this does not lead to significant 
problems in computing either the comfort or the energy consumption of 
the building. I often have situations in which I use a 1-5 minute time 
step and have to use a 1 hour wall time base in the building.

kind regards,

  David



On 09/11/2018 03:12, Noortje Alders via TRNSYS-users wrote:
>
> Dear TRNSYS users,
>
> I want to analyze the thermal behaviour of a dwelling with floor 
> heating in detail. Attatched is a drawing of the floor construction. 
> The time-base is set by 1 hour by default. I would like to set this 
> time-base to a lower value (eg 15 minutes or less) to be able to 
> analyse the reaction to change in occupancy with accordingly changing 
> ventilation, heating setpoint and internal gain. However, the high 
> thermla mass and high insulation value doesn't allow me to because the 
> stability criteria are not fullfilled. ("Error creating the wall 
> transfer coefficients: Stability criteria not fullfilled"). In a 
> previous thread of the forum (
> http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/2012-November/024387.html 
> ) I read that there is a "trick" for this. You can devide one layer in 
> the ground floor (e.g. the concrete slab) with an active layer. 
> However, if I try I get the message that only one active layer is 
> allowed. Is there another way to tackle this problem?
>
> Kind regards,
>
> Met vriendelijke groet,
> Noortje Alders
>
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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