Re: [TRNSYS-users] Cooling demand

Ciao Miriam,

mi hai detto prima che ti aspeteresti un valore di potenza di condizionamento di circa 60 kW, giusto?

Parli davvero di potenza di condizionamento o di energia di condizionamento (ossia kWh)?

Questo valore di 60 kW che tu vorresti ottenere da qualche calcolo lo hai ottenuto? E con quali condizioni al contorno?

Vorrei solo capire perché ti aspetti un certo valore e con cosa lo stai confrontando…

Toni Calabrese, MSc.

Wissenschaftlicher Projektleiter

toni.calabrese@spf.ch | toni.calabrese@ost.ch

T +41 58 257 4827

SPF Institut für Solartechnik

OST – Ostschweizer Fachhochschule

Oberseestr. 10 | CH-8640 Rapperswil | Switzerland | www.spf.ch | www.ost.ch

OST – Ostschweizer Fachhochschule ist der Zusammenschluss aus FHS St.Gallen, HSR Rapperswil und NTB Buchs.

From: TRNSYS-users <trnsys-users-bounces@lists.onebuilding.org> On Behalf Of miriam di matteo via TRNSYS-users
Sent: Wednesday, May 26, 2021 5:46 PM
To: TRNSYS users mailing list at OneBuilding.org <trnsys-users@lists.onebuilding.org>
Cc: miriam di matteo <dimatteo.1585179@studenti.uniroma1.it>
Subject: Re: [TRNSYS-users] Cooling demand - QCOOL

Ciao Toni,

grazie mille della risposta.

Ho dimenticato di scrivere che sto utilizzando Trnsys 17

per quanto riguarda la verifica con il .BAL (NType 904 / 905) l'ho effettuata, ho stampato singolarmente i diversi Output e confrontati con i corrispettivi B4_xxx. Precisamente:

- QSCOOL (NT. 33) -> B4_QCOOL (NT. 905 e 953)

- SDQAIR (NT. 39) -> B4_DQAIRdt (NT. 905 e 951)

- SQINF (NT. 35) -> B4_QINF (NT. 905 e 952)

- SQGCONV (NT 38) + SQGRAD (NT 43) -> B4_QGINT (NT 905 e 958)

- QSOLAIR (NT 117); di cui ho calcolato la somma tramite la Type calcolatrice) -> B4_QSOLAIR (NT. 905 e 961) Questo fattore è sempre 0, ma non ne comprendo il motivo;

- B4_QSOL (NT 905 e 960) non ho trovato l'esatto corrispondente, in diverse conversazioni ho letto di far riferimento a QTSABS (NT. 57)

- B4_QTRANS (NT 905 e 957) per come ho compreso il QTRANS non è possibile ottenerlo in via diversa se non mediante il Balance. In oltre non ne comprendo a pieno i risultati. Dalla descrizione sembra che valori positivi corrispondano a guadagni termici per la zona termica e valori negativi al contrario delle dispersioni verso l'esterno, per tanto non dovrei avere QTRNS+ con Tin<Tou e TRNS- con Tin>Tout? Chiedo perché questa cosa dai risultati della simulazione non risulta.

Per quanto riguarda i guadagni interni, si sono vicini a quelli ipotizzati.

Per quanto riguarda i guadagni solari (QSOL) sono inclusi nel SUMMARY, mentre il QSOLAIR come dicevo prima è sempre pari a 0. Se sono realistici o meno, ammetto che non sono bene in grado di definirlo. Ho cercato di far riferimento alla UNI 10349 e alla UNI 11300 per avere un idea dei valori che dovrebbero uscire (c.a. 57000 MJ nel mese di Luglio), e in effetti sono maggiori rispetto a quelli risultanti dalla simulazione di TRNSYS (36000 MJ nel mese di Luglio). L'edificio è situato nel Lazio, in provincia di Roma.

Provo a controllare meglio questi valori e le impostazioni corrispondenti.

In ogni caso allego il modello Trnsys e il .bdf, se hai modo di guardarlo te ne sono infinitamente grata.

Grazie Mille davvero.

I'm not sure that i answer only you (Toni) or to all User mailing list, so i Traslate the email in English too.

I forgot to write that I am using Trnsys 17.
As regards the verification with the .BAL (NType 904/905) I have done it. I have printed the different Outputs and compared with the corresponding B4_xxx. More precisely:
- QSCOOL (NT.33) -> B4_QCOOL (NT.905 and 953)
- SDQAIR (NT.39) -> B4_DQAIRdt (NT.905 and 951)
- SQINF (NT.35) -> B4_QINF (NT.905 and 952)
- SQGCONV (NT 38) + SQGRAD (NT 43) -> B4_QGINT (NT 905 and 958)
- QSOLAIR (NT 117); (of which I calculated the sum using the Type calculator) -> B4_QSOLAIR (NT. 905 and 961) This factor is always 0, but I don't understand why;
- B4_QSOL (NT 905 and 960) I did not find the exact correspondent, in several conversations I read about referring to QTSABS (NT.57)
- B4_QTRANS (NT 905 and 957) as I understood the QTRANS it is not possible to obtain it in different way except through the Balance. In addition, I do not fully understand the results. From the description it seems that positive values correspond to thermal gains for the thermal zone and negative values as losses, so I shouldn't have QTRNS + with Tin <Tou and TRNS- with Tin> Tout?

About the internal gains, they are close to those assumed.
As for the solar gains (QSOL) they are included in the SUMMARY, while the QSOLAIR as I said before is always equal to 0. Whether they are realistic or not, I admit they are not well able to define it. I tried to refer to UNI 10349 and UNI 11300 to get an idea of the values that should come out (about 57000 MJ in the month of July), and in fact they are greater than those resulting from the simulation of TRNSYS (36000 MJ in the month of July). The building is located in Rome.

In any case, I enclose the Trnsys model and the .bdf, if you have the opportunity to look at it I am infinitely grateful.
Thank you very much indeed.

Miriam

Il giorno mer 26 mag 2021 alle ore 13:44 Toni Calabrese via TRNSYS-users <trnsys-users@lists.onebuilding.org> ha scritto:

Hi Miriam, (if you speak italian please let me know ;))

Did you have a look to the SUMMARY balance that is automatically printed by trnsys? Are the values coincidents?

It is hard to say something without checking the model, but I can assume that the problem could be in the cooling itself, but it could be also in a wrong implementation of the boundary conditions. For example:

1. Did you check the solar gains (are also included in the SUMMARY balance)? Are realistic?

2. Did you check the internal gains? Are the outputs of internal gains equal to what did you expect?

Please send me in case the trnsys model and the bui file in order that I can help you in details.

Toni Calabrese, MSc.

Wissenschaftlicher Projektleiter

toni.calabrese@spf.ch | toni.calabrese@ost.ch

T +41 58 257 4827

SPF Institut für Solartechnik

OST – Ostschweizer Fachhochschule

Oberseestr. 10 | CH-8640 Rapperswil | Switzerland | www.spf.ch | www.ost.ch

OST – Ostschweizer Fachhochschule ist der Zusammenschluss aus FHS St.Gallen, HSR Rapperswil und NTB Buchs.

From: TRNSYS-users <trnsys-users-bounces@lists.onebuilding.org> On Behalf Of miriam di matteo via TRNSYS-users
Sent: Wednesday, May 26, 2021 1:03 PM
To: trnsys-users@lists.onebuilding.org
Cc: miriam di matteo <dimatteo.1585179@studenti.uniroma1.it>
Subject: [TRNSYS-users] Cooling demand - QCOOL

Dear all,

I have some questions about the cooling energy demand and the output "QCOOL" NType 31 and 33. I'm studying a residential building, and i need to know its Cooling demand. My problem is that the QCOOL value is very low. It is about 30kW, but the manually estimated value is more than double (>60kW). I don't understand if I did something wrong in the modelling or "QCOOL" isn't the Output that i need.

I followed this steps to realized TRNSYS model :

I did a geometrical model with TRNSYS 3D (Google SketchUp plugin), with its 13 apartments and whit the internal walls, windows and external shading devices (as walls, balconies etc...).
In TRNBuild i characterized Wall and Windows levers, and insert the Infiltrations and internal gain from people and light.
I know the characteristic of the boiler and radiators installed; The GAS bill about 2018 and 2019; Moreover I measured the trend of temperatures inside an apartment for 4 days. I calibrated my TRNSYS model with this data.
So I inserted in my Thermal zones a ideal Cooling: Temperature set point 26°C, unlimited, humidity off.

I followed a similar way for Heating demand, I used an Ideal Heating with a set point temperature of 20°C, unlimited, radiation part 20% and without humidification. I didn't observed any problem with Heating simulations.

Can you confirm me that "QCOOL" (NType 31 and 33) represent my cooling energy demand? In this case, if my TRNSYS model is correct the Value of QCOOL it is necessary correct, right? It means that I have to look for the error in the Trnsys model, is it true? Honesty i have no idea where the error might be, It seems to me that everything is correct. But it is the first time that i use Trnsys, so is easy that i insert a wrong parameters or forget something, i think. Anyone have any advice about it?

I hope someone can help me, it is very important. Thank all in advance

Miriam

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