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

[Noortje Alders]

Dear David,

Thank you for your answer. This is actually what I expected but hoped 
not to be the case. I think the energy consumption of the building can 
be calculated reliably; however, I would like to study the behaviour of 
the floor heating in more detail. I guess I have to decide from 
situation to situation which time-base to use, as the higher the 
time-constant (the slower the system), the less the time-base matters.

Met vriendelijke groet,
Noortje Alders


Postbus 696
2700 AR Zoetermeer
T: 079 3470309
E: n.alders at peutz.nl
W: www.peutz.nl
------------------------------------------------------------------------
Op 11-09-2018 om 16:02 schreef 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
>>
>>
>> Postbus 696
>> 2700 AR Zoetermeer
>> T: 079 3470309
>> E: n.alders at peutz.nl
>> W: www.peutz.nl
>> ------------------------------------------------------------------------
>>
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>>
>>
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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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