[TRNSYS-users] Temperature course and reaction time

Dols, William Stuart william.dols at nist.gov
Wed Oct 22 14:29:05 PDT 2014

Here are a couple of papers related to this topic.

Delcroix, B., M. Kummert, A. Daoud, and M. Hiller. 2012. Conduction transfer functions in TRNSYS multizone building model: Current implementation, limitations and possible improvements. in Fifth National Conference of IBPSA-USA (SimBuild 2012). Madison, WI.

Delcroix, B., M. Kummert, A. Daoud, and M. Hiller. 2013. Improved Conduction Transfer Function Coefficients Generation in TRNSYS Multizone Building Model, in 13th Conference of International Building Performance Simulation Association (BS2013): Chambery, France.

- Stuart

From: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org] On Behalf Of David BRADLEY
Sent: Wednesday, October 22, 2014 4:29 PM
To: TRNSYS users mailing list at OneBuilding.org; masood.mobarak at yahoo.com
Subject: Re: [TRNSYS-users] Temperature course and reaction time

  The steps are probably caused by a large difference between your simulation time step and your building's timebase. A wall's response to a change in ambient conditions is characterized by equations that have a series of coefficients each of which can be thought of as a relative weighting factor for a particular ambient condition stepping backwards in time. For example, there are some coefficients that tell how important the temperature difference across the wall was one time base ago, two time bases ago, three time bases ago, etc. You can set the timebase in TRNBuild (open the "outputs" window) and it is best if the timebase matches your simulation time step.
  I am not sure what simulation time step you are using but please bear in mind that many of the models in TRNSYS are not appropriate when used with tiny time steps. I would not recommend using a time step less than about 1 minute.
Kind regards,

On 10/22/2014 10:40, Masood Mobarak wrote:

Hi @ all,

I am writing my master thesis about room simulation and I am new to TRNSYS.

I have two question and i hope that you can help me:

1. Question: How comes that the temperature course of a room (type 56) has alsways jumps/steps.

For Example: When the ambient temperature is very cold then the temperature in the room falls, but in many little steps (See attachment).

Is this a fault from the simulation? If not can someone explain me why this course is correct ?

2. The temperature in the room falls immediatly after the ambient temperature falls. Is this also correct? I thought there have to be some time until the temperature from the room will react to the ambient temperature or to heating the room. When the heating power beginn the temperature begins to raise. I thought that there have to be some minutes until it will beginn to raise.

Kind regards,

Masood Mobarak


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