[TRNSYS-users] energy bilans for Type 56

Fri Nov 18 08:14:03 PST 2011

Dear Marcello,

It became more clear J - thank you very much. 

I have a few question to resume our conversation:

1)      It doesn’t meter if we consider ventilation, infiltration or
coupling flow, there is always true rule: if we define incoming air TRNBuild
assume the same amount of ‘outcoming’ air but without any destination? If we
would like to give this air destination to e.g. zone A we have define supply
air in this zone.

2)      If coupling flow is assumed that air “leave” part of its heat in
wall? (because wall has some heat capacity)? I can’t find some reason of
that in equation in manual but there is difference between balance with flow
as coupling flow and supply air. 

Regards

Karol

Sent: Friday, November 18, 2011 3:13 PM
To: karol.bandurski at put.poznan.pl
Subject: RE: [TRNSYS-users] energy bilans for Type 56

Dear Damien and Karol,

I agree that the way TRNSYS treats airflow rates between zones could appear
misleading. The main concept is that Type 56 has no airflow model (at least
if you do not have TRNFLOW). 

Indeed, Type 56 needs to know only incoming air, as it assumes, in order to
assume air balance of ONE ZONE, that An equal amounts of air is assumed to
leave the airnode at the airnode temperature. The destination of the leaving
air has no interest from the point of view of the zone.

If you have two zones without infiltrations and ventilation, and one opened
door between them, there will be an air exchange between the two zones. For
mass balance, the mass airflow rate going from zone A to zone B should be
the same than the mass airflow rate from zone B to A. However, in this case,
type 56 DOES NOT CHECK air balance, then it is to you to define the two
airflow rates with the same value. This is the meaning of the sentence in
the section 5.4.1.2: coupling air flow from B to A is not defined
automatically.

Therefore, your last sentence is correct, Karol: if you define air from A to
B as coupling flow then TRNBuild assume that the same amount of air leaves
zone B, BUT IT DOES NOT ASSUME that this air is going to zone A.

About the difference between coupling air flow through wall and between air
node, I think that there Is no difference. The possibility to have coupling
air flow between nodes has be introduced in TRNSYS 17 because two air nodes
could have no adjacent walls.

Best regards.

Marcello CACIOLO
Responsable Outils et Méthodes d'Analyse Energétique 
___________________________________________________ 

logo AximaSeitha

Cellule Efficacité Energétique

Direction Commerciale 
46 Boulevard de la Prairie au Duc BP 40119
44000 Nantes Cédex 2
Tel. 02 40 41 06 57

mail: marcello.caciolo at aximaseitha-gdfsuez.com

www.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 Karol Bandurski
Envoyé : vendredi 18 novembre 2011 13:37
À : 'Damien Gondre'
Cc : trnsys-users at cae.wisc.edu
Objet : Re: [TRNSYS-users] energy bilans for Type 56

Damien,

There is something not clear corresponding to issue of coupling flow.

On one hand we have information from section 5.4.1.2 in Multizone Building
Manual, page 145 that if I define coupling flow from A to B then I have to
take care about balance on my own because coupling air flow from B to A is
not defined automatically.

On the other hand there is information in section 5.4.1.11, page 156
(similar to ventilation issue, but a few sentences later, corresponding to
coupling air flow): "An equal amounts of air is assumed to leave the airnode
at the airnode temperature".

Thirdly I hope that we distinguish coupling air flow through wall (p.125
section 5.2.11.8.5. - this is in the range of my interest) and coupling flow
between two airnodes of one zone (p.85 section 5.2.4.10.)

My previous statement should read:

“But if you define air from A to B as coupling flow then TRNBuild assume
that the same amount of air leave zone B as QTRANS.”

We are looking for Big Explanatory! ;)

Regards

Karol

From:  <mailto:damien.gondre at gmail.com> damien.gondre at gmail.com
<mailto:[mailto:damien.gondre at gmail.com]> [mailto:damien.gondre at gmail.com]
On Behalf Of Damien Gondre
Sent: Friday, November 18, 2011 11:05 AM
To: Karol Bandurski
Cc:  <mailto:trnsys-users at cae.wisc.edu> trnsys-users at cae.wisc.edu
Subject: Re: [TRNSYS-users] energy bilans for Type 56

Hi Karol,

I had the same questions a while ago and someone else would probably gives
you more trustable answers than me. But I will try to answer you with what I
figured out (someone please corrects me if I'm wrong).

"It is mean that if I introduce some supply air (ventilation manager) in
zone then TRNBuild assume that there is also exhaust air?"  

This is true. If you introduce in zone A 50m3/h of air at Tout for instance,
Trnsys will assume that the same amount of air (50m3/h) leaves zone A at
temperature of zone A (T_A).

"Then you define ventilation for zone B and parameters of air will be taken
from zone A"

That is what I would naturally do but it actually causes convergence
problems: if you use T_A to define parameters of air supplied to zone B by
the ventilation type, you will use an output of type 56 as an input to type
56. Air supplied in zone B will change temperature in zone B and it will
affect temperature in zone A (since zone A and B have an adjacent wall).
Then the temperature of air supplied in zone B will change and it will
change temperature in zone B and
 temperature in zone A (and so on
). 

If you still want to do that, you need to use type 93 (input value recall)
to supply air with temperature of zone A at timestep (t-1), in zone B at
timestep (t).

“But if you define air from A to B as coupling flow then TRNBuild assume
that the same amount of air leave zone B as coupling flow, not as exhaust
air”

That is not true. If you define air from A to B as a coupling flow TRNBuild
doesn’t assume automatically that the same amount of air flows from B to A.
(See the note in section 5.4.1.2 in Multizone Building Manual, page 145).
When you use coupling flows you have to perform air balance by yourself
which means that if you define a coupling from A to B, you will overload
zone B. 

How do you define exhaust air in zone B to balance the coupling flow from
zone A? I don’t know :). Maybe someone else can tell us more about this
 I’m
looking for this answer too!

Damien.

On Fri, Nov 18, 2011 at 10:13 AM, Karol Bandurski
<karol.bandurski at put.poznan.pl> wrote:

Hi!

Thanks for this quotation Damien but I don’t understand what is mean.

It is mean that if I introduce some supply air (ventilation manager) in zone
then TRNBuild assume that there is also exhaust air?  

Let us assume the situation:

I have ventilator in zone A but there is no ventilator in zone B. Between
zone A and B is wall with door. I calculated that air supply to zone A flows
to zone B.

This quotation say to me (in above situation):

you should define ventilation for zone A (supply air) then TRNBuild assumes
the same amount of exhaust air for this zone but without any destination.
Then you define ventilation for zone B and parameters of air will be taken
from zone A, TRNBuild again assume the same amount of exhaust air, without
any destination. But if you define air from A to B as coupling flow then
TRNBuild assume that the same amount of air leave zone B as coupling flow,
not as exhaust air.

1)       It is true???

If YES: 

2)      What does TRNBuild assume for infiltration? If during infiltration
air is supplied to zone then how it is ejected form there?  

3)      If coupling flow is assumed then air “leave” part of its heat in
wall? (because wall has some heat capacity)

Thanks again Damien for you tip, but

I am asking for more explanation!

Regards

Karol

From: Damien Gondre [mailto:damien.gondre at insa-lyon.fr] 
Sent: Thursday, November 17, 2011 2:26 PM
To: Karol Bandurski
Cc: trnsys-users at cae.wisc.edu
Subject: Re: [TRNSYS-users] energy bilans for Type 56

Hi Karol,

I have never used energy balances for zones so I don't know what Qvent,
Qtrans or Qsolgain represent, but have you looked in the multizone building
manual, section 5.4.1.11, page 156 : "Equal amounts of air are assumed to
leave the airnode at the airnode temperature".

I don't know if it helps or not, but I think it might change your vision of
how the energy balance is defined.

Regards,

Damien.

On Thu, Nov 17, 2011 at 1:28 PM, Karol Bandurski
<karol.bandurski at put.poznan.pl> wrote:

Hi,

I has modeled two version of one family house: 

a. with mechanical ventilation

b. with natural ventilation + exhaust fans in dirty rooms (bathroom, WC,
Kitchen) 

Then I has define balance output Ntype 904 (Energy Balance for Zones) for
one zone of this house.

The balance is seems to me false because in TRNBuild in Ventilation Manager
I can define only supply air ventilation. So, QVENT represents only heat
from supply air, heat connect with exhaust air is probably contained in
QTRANS. QTRANS has influence on temperature of walls, so maybe QSOLGAIN is
also not so accurate? 

My question:

It is true? 

How can I change it?

Does TRNFlow change this imperfection? (I don’t have this soft, I has only
Contam)

Regards,

Karol

------------------------------------------------

Karol Bandurski MSc.

 <http://www.ee.put.poznan.pl/> Institute of Environmental Engineering

Poznan University of Technology

 <http://www.ee.put.poznan.pl/> www.ee.put.poznan.pl

www.put.poznan.pl <http://www.put.poznan.pl/> 

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