Re: [TRNSYS-users] Decrease of temperature with Type 56

2011/6/7 Marion Hiller <hiller@transsolar.com>

Augustin,

Assuming no infiltration/ventilation the behaviour of the zone air temperature as well as the operative temperature after switching

off gains depend on the surface temperatures.

I run the attached files, but the entities on the online weren’t sufficient to see your problem (Top and Text).

If you talk about temperature are you looking at Top or Tair?

You may check surface temperatures TSI and the NTYPE QCOMI for heat transfer.

I suggest add Onlines with all relevant entities like TSI, TAIR, QCOMI, rad. GAINS, conv. Gains etc. .

Marion

Von: Augustin CUQ [mailto:augustin.cuq@gmail.com]
Gesendet: Montag, 6. Juni 2011 18:17
An: Aaron J. Danenberg
Cc: trnsys-users
Betreff: Re: [TRNSYS-users] Decrease of temperature with Type 56

Dear Aaron,

Thanks for answering so quickly.

Changing the infiltration rates (setting it to 0) doesn't change the phenomenon I describe... I had tried but the decrease can still be observed. Concerning the weather data, I wanted to simplify as much as I could the model, to be sure the problem wasn't the result of the weather variations. If you delete the heating device (or set it to 0) and the soil temperature too, you will see that the temperature decreases logically up to 0°C.
The conditions for the external walls are set to a default value 0, in order to be sure the evolution of the temperature remains constant (increase when there is a heating device and decrease when there is no heating device). In that way, the temperature shouldn't increase after stopping the heating device (it is the case in my simulation for the third time step following the interruption of heating), and it shouldn't decrease so fast for the two time steps following this interruption (comparing with the evolution after 4 time steps = 1 hour).

BR.

Augustin CUQ

2011/6/6 Aaron J. Danenberg <danenberg@hartford.edu>

Augustin,

You infiltration rates seem relatively high (0.6ACH), if it is this high I would assume you are in a windy location, or the building is old and leaky (or you include some mechanical ventilation in this number). Since the building is well insulated, I would assume the problem lies within your control (signal) scheme, or double checking your ACH assumption against the results of a blower door test. I use the data reader and TMY2 weather data to define the conditions for external walls. I did not understand how you defined your conditions for the external walls, that may be something you want to double check on, I cannot say if it is incorrect or correct, but may be a likely source of your problems.

Aaron J. Danenberg

Graduate Research Assistant

University of Hartford

From: Augustin CUQ [mailto:augustin.cuq@gmail.com]
Sent: Monday, June 06, 2011 10:03 AM
To: trnsys-users
Subject: [TRNSYS-users] Decrease of temperature with Type 56

Dear all,

I sent a mail two weeks ago to expose the problem I had but it was not very clear. So I have made an Excel file to illustrate it.The model has been simplified.

It represents a two rooms building, with no internal gain. The outside temperature remains constant to 0°C and all the other parameters used by the .bui are equals to a default value: 0.
The only parameter which is a variable input of the model is a heating power. It remains constant until the steady state is obtained and then it is put to 0.

The variation of the temperature, for the three time steps following the stop of the heating device seems to be weird. The decrease of the temperature is very fast, then it increases (???) before going down with an acceptable derivative value (around 0.3°C/hr).
Find attached the model I have used.

Can anyone explain to me the reason of this phenomenon?
Thanks in advance.

Best regards.

--
Augustin CUQ

--
Augustin CUQ

Elève-Ingénieur en dernière année à l'Ecole des Mines de Nantes,

Spécialisation en Génie des Systèmes Energétiques

Stagiaire chez ETAMINE, Bureau d'Etudes Techniques en thermique et aéraulique et en conseil HQE