[TRNSYS-users] Air treatment unit / ground temperature model

Thu Jul 5 08:00:00 PDT 2012

thanks a lot for ur answers!
Difficult to make a choice between using type ground temperature and using
a constant, I will try both and I will let u know the difference.

Many thanks for ur help

Faustine

2012/7/5 Jean Marais <jeannieboef at gmail.com>

> The Trnsys Models are similar to this program that energy plus uses. As
> I'm more familiar with eplus, I am pointing you to these references. The
> principles are the same. The isothermal diagrams showing soil temperature
> under the slab is interesting for you.
>
>
> slab program uses a 3D explicit finite difference scheme to solve the heat
> diffusion equation.
>
>
>
> It is based on the PhD dissertation by William Bahnfleth:
>
>
>
> Bahnfleth, W. (1989). Three-Dimensional Modeling of Heat Transfer from
> Slab Floors. University of Illinois at Urbana Champaign.
>
>
> http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA210826
>
>
> see also:
>
> http://www.dtic.mil/dtic/tr/fulltext/u2/a241567.pdf
>
> and
>
>
> http://apps1.eere.energy.gov/buildings/energyplus/pdfs/energyplus_slab-on-grade_tests.pdf
>
>
> ....to clarify the statement mentioned below: I suggest one calculates the
> u-value (which is usually very resistive), and then apply a steady state
> deltaT to get a "quick check" result for the heat flux lost or gained
> through the slab. You will notice that mostly the W/m² of heat transfer
> through the slab is quite small. This obviously depends on climate type and
> building, but is not a bad generallization. The errors of W/m² from
> inaccurate slab assumption, in relation to the errors inherrent in building
> modelling due to unknown user profiles and user habits, natural
> ventilation, etc. are far greater. Having more accurate scheduling usage
> and equipment controlling are far more benifitial in my opinion. For
> example, it is often assumed that the person load is 120 W/person...where
> in actual fact this is quite a big assumption in facilities such as
> schools. Another good point is building infiltration, which is either
> assumed or calculated with large assumptions as to window usage by users. A
> lot of modlers will simply put a fixed infliltration rate of 0.3 ACH for an
> entire building.
>
>
> Use the slab programs (types) if you have mastered some of the other
> aspects of building modelling, like intergrating COMMIS (CONTAM) or can
> better use the other infiltration models. Do "back of the cigarette packet"
> calculations to check if it is worth while using the slab program, before
> delving into it. As with all things, the actual answere is always "it
> depends".
>
>
> If you are in a warm climate, you may find using the slab programs are a
> must...but it depends. ;-)
>
>
> I had some other interesting links, but I can't find them now...will check
> agian later.
>
>
> All the best.
>
>
> On 5 July 2012 09:34, <marcello.caciolo at cofelyaxima-gdfsuez.com> wrote:
>
>>  Dear Jeannieboef,****
>>
>> ** **
>>
>> I am really interested in modelisation of heat exchange of a building
>> with the ground. Could you post the reference you mentioned?****
>>
>> ** **
>>
>> By the way, you say “the added accuracy [of modeling heat exchange with
>> the ground] to yearly energy consumption is not that big”. Could you
>> precise if this sentence is based on your feeling, on your experience or on
>> some published results? In my experience, it really depends on the building
>> type and on the ratio between height and floor area.****
>>
>> ** **
>>
>> Thank you for your help.****
>>
>> ** **
>>
>> Best regards,****
>>
>> ** **
>>
>> *Marcello Caciolo*
>> Responsable Outils et Méthodes d'Analyse Energétique****
>>
>> [image: cid:image003.jpg at 01CD4E08.954D04D0]
>> *
>> *Cellule Efficacité Energétique et Environnementale - Pôle Projets et
>> Réalisations
>> 46 Boulevard de la Prairie au Duc
>> BP 40119 - 44201 Nantes Cedex 02
>> Tél.: +33 02 40 41 06 57
>> marcello.caciolo at cofelyaxima-gdfsuez.com<prenom.nom at aximaseitha-gdfsuez.com>
>> ****
>>
>> P *Pensez à l'environnement avant d'imprimer ce message*****
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> *De :* trnsys-users-bounces at cae.wisc.edu [mailto:
>> trnsys-users-bounces at cae.wisc.edu] *De la part de* jeannieboef
>> *Envoyé :* mercredi 4 juillet 2012 18:41
>> *À :* Herve Gaël
>>
>> *Cc :* trnsys-users at cae.wisc.edu
>> *Objet :* Re: [TRNSYS-users] Air treatment unit / ground temperature
>> model****
>>
>>  ** **
>>
>> Just to re-itterate one of my favourite subjects...****
>>
>> The ground temperature objects are good to use with anytype of ground
>> heat exchanger (for example the two mentioned by David, namely earth tubes
>> and Geothermal). It should, however not be used as the boundry condition on
>> the ground bounding contructions of conditioned spaces. This is inaccurate
>> and a mistake I am seeing often by Trnsys users. If using a constant value,
>> I suggest the mean (day + night) monthly conditioned space temperature
>> minus 2 Kelvin, for bounding constructions in the range of 150 to 300 mm
>> without insulation.****
>>
>> ** **
>>
>> If you want to accurately model this, I suggest using the slab/basement
>> types that do the 3d calculation for this. If you are a begginer, don't
>> focus your efforts here as the added accuracy to yearly energy consuption
>> is not that big. If you do use the complex modelling types also bear in
>> mind the effects of ground water level on apparent soil temps.****
>>
>> ** **
>>
>> If anyone is really interested, I can post the links to some papers about
>> this topic when I'm back at my desk tomorrow.****
>>
>> ** **
>>
>> ---****
>>
>> ** **
>>
>>
>>
>> Sent from my iPhone****
>>
>>
>> On 04.07.2012, at 14:00, Herve Gaël <G.Herve at ciat.fr> wrote:****
>>
>>  Francis,****
>>
>>  ****
>>
>> You want to analyze your energy performance in heating and cooling, so
>> first of all, I think you should do two separate simulations, one in
>> heating and the other in cooling mode.****
>>
>> I suppose that what you need to know is the power injected by your
>> terminal unit in each room depending of the delta of temperature between
>> the set point and the real temperature. You don’t need to know the blowing
>> temperature and the flow rate… I think your solution is creating a multi
>> dimensional data interpolation in a file function of water temperature,
>> speed of blowing, etc… ****
>>
>> I hope this can help!****
>>
>>  ****
>>
>> Best,****
>>
>>  ****
>>
>> *___________________________________*****
>>
>> *Gaël HERVE*****
>>
>> Ingénieur Numéricien LQAI****
>>
>> Avenue Jean Falconnier****
>>
>> 01350 CULOZ****
>>
>> Tél: +33 (0)4 79 42 64 30****
>>
>> Fax : +33 (0)4 79 42 40 13 ****
>>
>> *De :* trnsys-users-bounces at cae.wisc.edu [
>> mailto:trnsys-users-bounces at cae.wisc.edu<trnsys-users-bounces at cae.wisc.edu>]
>> *De la part de* Francis KERBER
>> *Envoyé :* mercredi 4 juillet 2012 08:37
>> *À :* David BRADLEY
>> *Cc :* trnsys-users at cae.wisc.edu
>> *Objet :* Re: [TRNSYS-users] Air treatment unit / ground temperature
>> model****
>>
>>  ****
>>
>> Dear David and Jean,****
>>
>>  ****
>>
>> Many thanks for your answer. I just need the ground temperature to
>> modelise my basement. In my bui. I use an input Tsoil for "boundary
>> userdefined" that's all. I will use your values if I don't find any.****
>>
>>  ****
>>
>> Otherwise to answer Jean question, I want to modelise to analyse energy
>> performance, and to compare to reality my heat and cool needs.****
>>
>>  ****
>>
>> Many thanks.****
>>
>> Hope u will be able to answer to my second question about my air
>> treatment unit and the final regulation system.****
>>
>>  ****
>>
>> Francis****
>>
>> 2012/7/3 David BRADLEY <d.bradley at tess-inc.com>****
>>
>> Francis,
>>   There is no difference between Type77 and Type501. The component
>> started out in the TESS Libraries as Type501 but was donated to the
>> standard library and given a new number. It is still in the TESS Libraries
>> for backward compatibility. The thing to remember about that model is that
>> it is an undisturbed ground temperature model meaning that no matter how
>> much energy you remove from the ground or add to the ground, the ground
>> temperature will only ever be a function of the time of year. If you are
>> using this in a geothermal application where you are rejecting energy to
>> the ground and removing energy from the ground, the ground temperature will
>> be impacted and you should look at using Type557. If you are drawing air
>> through tubes in the ground then you should look at using Type460 (Pierre
>> Holmuller's earth duct model as implemented by Transsolar)
>>
>>   If you aren't able to find data for Type501 then the following will get
>> you started: For the mean soil temperature, use the average annual air
>> temperature for your location. For the amplitude, plot out the monthly
>> average temperature for your location and calculate the biggest difference
>> between the average annual temperature and the monthly average
>> temperatures. For the time shift, use 30.
>>
>> Best,
>>  David ****
>>
>>
>>
>>
>>
>> ****
>>
>> On 7/2/2012 09:21, Francis KERBER wrote:****
>>
>>   Dear all,****
>>
>>  ****
>>
>> I'm quite new on trnsys and I have few questions about my modelisation.**
>> **
>>
>>  ****
>>
>> Firstable, I'd like to simulate the ground temperature instead of using a
>> constant, which is less precise. I heard about type 501 and type 77. Is
>> there any difference between those types? Which one is the best? Moreover,
>> where to find the informations the type needs as inputs, like mean soil
>> temperature, amplitude of Paris...?****
>>
>>  ****
>>
>> My project includes a Air treatment unit with a wheel heat exchanger, two
>> fans, and two batteries (warm water and cold water batteries). I get a
>> final regulation system, wich is a ventilating and cooling or heating
>> system (by warm water and cold water batteries as well), depending on the
>> set temperature. I do understand the system but I don't really know how to
>> modelise it. Is ther any existing type I can use? Should I detail each
>> system like my fans, my batteries...which seems to be complicated.****
>>
>> Moreover if I have this final regulation system in each room, must I
>> create as much types as number of rooms?****
>>
>>  ****
>>
>> If u have any idea that would be helpful!!!!!****
>>
>>  ****
>>
>> Thanks a lot for ur answers****
>>
>>  ****
>>
>> Francis.****
>>
>>  ****
>>
>> _______________________________________________****
>>
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>>
>> TRNSYS-users at cae.wisc.edu****
>>
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>>
>>
>>
>>
>> ****
>>
>> -- ****
>>
>> *******************************
>>
>> David BRADLEY****
>>
>> Principal****
>>
>> Thermal Energy Systems Specialists, LLC****
>>
>> 22 North Carroll Street - suite 370****
>>
>> 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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>>
>>
>
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