Surface heat flux

Irene.Pau · Posts: 20

Hi Andy,

I have a few additional questions related to my previous surface heat flux query:

1) Is it possible to obtain heat flux values in DB from a single surface to the zone? From what I understand after reading your response, the DB results show the heat flux going through the surface itself. I would like to be able to get the heat flux out of the surface and into the zone.

2) May I also obtain surface temperatures for the different surfaces within my model?

3) What does E+/DB actually do when we specify an adiabatic surface? When I look at the surface heat flux for an adiabatic floor, for example, it seems to be losing a lot of heat through the surface during the day (for a summer day), which is not what I would expect. Does the surface "see" the external temperature, or does it actually model it as though there were an adjacent zone with similar internal conditions?

Thanks again,
Irene

Laurent_Support · Posts: 292 Location: Vincennes

Hello Irene,

george_s · Posts: 12

I have the same wonder about the adiabatic surfaces. When we are talking about "adiabatic" surface most of us have in mind a "wall" (or whatever) that its presence in the building does not influence in any way the heat flow. However, as you very well said there is a thermal mass that affect the behavior of this surface.

But as i can see in DB (i tried different material for ground floor) it seems that this infuence of thermal mass is bigger than I expected. For example the gain and losses from gound floor for a simple model (13mx15m default values) during a summer day (15 jul, London) have higher values (!) when i set the ground floor as an aniabatic surface than when it is "auto". This seems to be a bit strange, don t you think ? or is there something i missing ?

thanks

Laurent_Support · Posts: 292 Location: Vincennes

Hello,

The first idea explaining your ground floor has such influence could be that ground temperature (in Localization tab) is set at a low temperature.

Default value for ground temperature are 14°C for every months, too low to take into account the building effect on the ground.
For example, if internal temperature is 25°C, you have a delta T of 11° (internal - ground temp.). With adiabatic ground floor the delta T is 0° and of course change greatly zone heating balance.

If it is not your case, please give me more data about your settings.

Thanks,
Laurent

ceck · Posts: 48 Location: Padova

Having a surface solar flux would be useful to include photovoltai or solar panels.

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