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

Tue Sep 11 07:48:11 PDT 2018

Noortje,

   There is another alternative as well, which is Type1267. It is a 
finite difference model that we wrote to really dig into the coupling 
between buildings and the surrounding ground. It is somewhat tricky to 
set up and it runs slowly, however, it can model almost any 
configuration you want. You can set up basements, partial basements (ie 
where the ground slopes), etc. You can also embed pipes in the soil or 
in the slab. Essentially what you are doing in this case is taking the 
floor model out of Type56 and using this finite difference approach 
which does not rely on transfer functions and does not have a time base. 
The one thing that might be tricky for it is to deal with a situation 
where you've got a radiant slab between two floors in the building (as 
opposed to in a floor that has some combination of insulation and soil 
on the back side of it).

David

On 09/11/2018 09:33, Noortje Alders wrote:
>
> 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
>>> ------------------------------------------------------------------------
>>>
>>> Klik hier <http://www.peutz.nl/index.php?pageid=109> om u aan te 
>>> melden op de Peutz Actueel
>>> Klik hier <http://www.peutz.nl/index.php?pageid=105> voor het 
>>> cursusoverzicht van Peutz Academy
>>> E-MAIL DISCLAIMER: http://www.peutz.nl/disclaimer/emaildisclaimer.html
>>>
>>>
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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
>
>
> Klik hier <http://www.peutz.nl/index.php?pageid=109> om u aan te 
> melden op de Peutz Actueel
> Klik hier <http://www.peutz.nl/index.php?pageid=105> voor het 
> cursusoverzicht van Peutz Academy
> E-MAIL DISCLAIMER: http://www.peutz.nl/disclaimer/emaildisclaimer.html 

-- 
***************************
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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