Re: [TRNSYS-users] Problem with Active Layer

Hi David and thanks for your answer. I tried, as I wrote to David, to increase the total mass flow rate of the system but it does not work anyway. I tried as well to set the "manual geometry" in order to segment the active layer but it does not work.

If I set a pipe distance to 13 cm, it works, but if I reduce the distance to 10 cm, it does not work anymore even if I segment the active layer or I increase the total mass flowrate through the pump of the system or if I increase the minimum desired mass flow rate through the active layer to at least 1.1 of the minimum.

Is there no other way to solve this problem?

Attached the files of my model. Maybe you can help me…

Toni Calabrese, MSc.

Wissenschaftlicher Projektmitarbeiter

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 David Offtermatt via TRNSYS-users
Sent: Tuesday, February 9, 2021 8:38 AM
To: TRNSYS users mailing list at OneBuilding.org <trnsys-users@lists.onebuilding.org>
Cc: David Offtermatt <david.offtermatt@hft-stuttgart.de>
Subject: Re: [TRNSYS-users] Problem with Active Layer

Hi Toni

I assume that by reducing the distance, the tube length has also increased. Does this happen?
By approximating the ACT layer, the return temperature can drop below the core temperature because the fluid temperature decreases over the length of the tube. To avoid this, you need a minimum mass flow. In order to reproduce a realistic temperature curve, you can make the layers smaller. But be carefull with the IN and OUT temperature.

Here you will find a detailed description: "Koschenz, Markus / Lehmann, Beat: Thermoaktive Bauteile tabs. [1. Aufl.], Dübendorf: EMPA Energiesysteme/Haustechnik, 2000. S.25"

kind regards from antohter David

Von: TRNSYS-users <trnsys-users-bounces@lists.onebuilding.org> im Auftrag von David BRADLEY via TRNSYS-users <trnsys-users@lists.onebuilding.org>
Gesendet: Montag, 8. Februar 2021 15:06:48
An: TRNSYS users mailing list at OneBuilding.org
Cc: David BRADLEY
Betreff: Re: [TRNSYS-users] Problem with Active Layer

***** ACHTUNG! Dies ist eine externe Mail. Öffnen Sie keine Anhänge und klicken Sie nicht auf enthaltene Links, solange Sie dem Absender nicht trauen und wissen, dass der Inhalt sicher ist *****

Toni,

I have run into this problem from time to time as well and was never able to discover the cause. I found that if I increased the flow rate to about 1.1 times the stated required flow the the error usually went away. The other thing you can do, of course, is to segment the floor so that it will allow you to enter the flow that you wanted.

kind regards,

David

On 02/08/2021 03:08, Toni Calabrese via TRNSYS-users wrote:

Hi everyone,

For a pilot project we are analyzing a heating system in which an "external wall heating system" is installed on the façade. Basically we have a wall with an active layer that is insulated on the back in order to decrease the losses of this active layer to the outside.

With a pipe spacing of 13.5 cm the system was working good. For a parametric study, I would like to run a study varying the pipe spacing. Setting the pipe spacing to 10 cm (instead of 13.5 cm) the system does not simulate anymore. It gives me the following error:

Message               : Specific fluid mass flow of active layer in surface   24 below minimum value of 8.01 kg/m2h Please, increase the minimum mass flow rate or use the autosegmentation feature of TRNBuild for subdividing the surface.

I checked the massflow rate and I am sure that the mass flow rate is higher than the minimum. I tried to increase the massflow rate through the pump of the system but it does not work. Which is the problem?

Here the data of my simulation:

1.     TRNSYS 17

2.     Wall area: 10.16 m2

3.     Massflow rate system: 86 kg/h

Toni Calabrese, MSc.

Wissenschaftlicher Projektmitarbeiter

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.
_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@lists.onebuilding.org
http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org

--

***************************

David BRADLEY

Principal

Thermal Energy Systems Specialists, LLC

3 North Pinckney Street - suite 202

Madison, WI  53703 USA

P:+1.608.274.2577

d.bradley@tess-inc.com

http://www.tess-inc.com

http://www.trnsys.com