Re: [TRNSYS-users] shady place simulation

Karol,

as always there is possibility to model it with Trnsys J.
However the modelling is more complex because you have to make sure that the modelling assumptions still yield to a valid result.

The basic idea is to model the “semi-outdoor space” as an “indoor space” and you have think about how the main thermal processes

are modelled:

- short-wave radiation (direct and diffuse)

- long-wave radiation

- convection

- humidity

- comfort

For example:

short-wave radiation (direct and diffuse)

- depending on the size and distribution of the holes you can use the so-called “no window” with a 100 % transmittance
and the leaf part as an opaque surface with a solar absorptance or model the “leaf roof” as a single layer window with
an approximated optical properties.

- The direct distribution model is fine, for the diffuse radiation you need to check if the model is adequate.

- ….

Long-wave radiation

- What is the temperature of the “leaf roof” for long-wave radiation exchange within space?
Do the holes have to have sky temperature?

- …

Convection

- What input values do you have? Can a nodal model like TRNFlow solve this or do you need a CFD to define the ventilation rates?

- ….

Humidity

- Do you need to take into account the impact of vegetation with respect to humidity and cooling effects?

- ….

The success really depends on your project and what the aim of the simulation.

Marion

Dipl.-Ing. Marion Hiller

Transsolar Energietechnik GmbH

Curiestraße 2

70563 Stuttgart
Telefon: +49 711 67976-0
http://www.trnsys.de

Transsolar: KlimaEngineering- Technologien für energieeffizientes Bauen und Nutzerkomfort in Gebäuden

Stuttgart – München – New York – Paris

Geschäftsführer :Diplom-Ingenieur Matthias Schuler, Diplom-Ingenieur Thomas Auer, Diplom-Physiker Stefan Holst, Diplom-Betriebswirt Dieter Schnelle

Eingetragen beim Amtsgericht Stuttgart HRB 23347,

Steuernummer: 99073/00911,USt-IdNr.: DE 152272639

Von: TRNSYS-users [mailto:trnsys-users-bounces@lists.onebuilding.org] Im Auftrag von Karol BANDURSKI
Gesendet: Freitag, 13. Juni 2014 16:39
An: TRNSYS-users@lists.onebuilding.org
Betreff: [TRNSYS-users] shady place simulation

Dear Users and Developers,

I would like to model the zone that envelope is ‘fully of holes’, it consists of only shading elements. Like space inside upper branches of a tree or in the forest.

So, there is no thermal insulation and air and heat can flow into and across zone by natural ventilation, but sun radiation is limited.

I wonder if TRNSYS simulation (TRNBUILD+TRNFLOW) can be appropriate to model such objects (inside thermal comfort) or it is necessary to use CFD simulation.

I think to prepare zone (maybe a few airnodes) with very low thermal resistance (or thermal properties of construction material, e.g. steel) and with a lot of cracks in the walls, then to model shading elements using shading zones.

Do you have some idea or some experience with such objects?

Any comments, hints and tips are appreciated!

Kind regards,

Karol

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

Karol Bandurski MSc.

Institute of Environmental Engineering

Poznan University of Technology