[TRNSYS-users] TRNFLOW

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Hi everyone,

I'm currently learning the use of TRNFLOW. To make it simple, I designed
a 1m3 box with SketchUp.
In TRNSYS:
- Firstly I just observed the air temperature inside the box without any
incoming thermal perturbation
- Secondly I set up a large opening (window) with an opening schedule.

The result is:
In the second case, I do observe a dramatic decrease of the temperature
inside the box when the window is opened. However, right after it is
closed, the temperature "jumps" to the temperature in the first case. To
say it briefly, when I put the two graphs together, the only difference
is when the window is opened. For the rest, it matches almost perfectly.

It shouldn't be like that since the outside air temperature is far below
the inside temperature. I expected the same temperature in both cases
before the windows is opened. Then a dramatic decrease of the
temperature when the window is opened. And after closing the window, I
expected the temperature to slowly decrease according to the outside air
temperature, keeping a temperature difference between the two cases.

Do you have any idea of the problem?
(there is not heating in my model)

Wirich Freppel

freppelw at noirot.fr's picture
Joined: 2016-04-05
Reputation: 0

Dear Wirich,

your zone is very small and has a small zone capacity, too.

The cooling due to the opening has a small impact compared to the heat transfer through window and walls.

Increasing the zone capacity or changing your zone to 5x5x5m? geometry will show the effects that you were expecting.

If you use a small or no window, the effect can be seen even better.

Best regards
Jakob

_________________________________________________________________________________________________

Jakob Merk

TRNSYS Software Team

Transsolar Energietechnik GmbH

Curiestra?e 2

70563 Stuttgart

Fax: +49 711 67976-11

Email: hotline at transsolar.com

Web: www.trnsys.de

-----Urspr?ngliche Nachricht-----
Von: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org] Im Auftrag von freppelw at noirot.fr
Gesendet: Freitag, 11. M?rz 2016 10:26
An: TRNSYS-users at lists.onebuilding.org
Betreff: [TRNSYS-users] TRNFLOW

Hi everyone,

I'm currently learning the use of TRNFLOW. To make it simple, I designed a 1m3 box with SketchUp.

In TRNSYS:

- Firstly I just observed the air temperature inside the box without any incoming thermal perturbation

- Secondly I set up a large opening (window) with an opening schedule.

The result is:

In the second case, I do observe a dramatic decrease of the temperature inside the box when the window is opened. However, right after it is closed, the temperature "jumps" to the temperature in the first case. To say it briefly, when I put the two graphs together, the only difference is when the window is opened. For the rest, it matches almost perfectly.

It shouldn't be like that since the outside air temperature is far below the inside temperature. I expected the same temperature in both cases before the windows is opened. Then a dramatic decrease of the temperature when the window is opened. And after closing the window, I expected the temperature to slowly decrease according to the outside air temperature, keeping a temperature difference between the two cases.

Do you have any idea of the problem?

(there is not heating in my model)

Wirich Freppel

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TRNSYS-users mailing list

TRNSYS-users at lists.onebuilding.org

http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org

hotline's picture
Offline
Joined: 2016-04-05
Reputation: 0

Dear Wirich,

I will suggest you to increase the zone capacitance to at least ?20-25
times of zone volume. If you model zone consists lot of furniture's then
make it 30-35 times of zone Volume.

As suggested by Jacob please consider bit larger geometry.

Regards,

Manoj

manoj kumar singh's picture
Joined: 2016-04-05
Reputation: 0