Auxiliary energy

[Julian]

Dear community,

I have created two different models. One of them is a 3 storey building and the other is a 7 storey building. Both have the same total floor area.

I have set an auxiliary ventilation air flow of 1,2 l/s·m2 under 'Air Exchange' tab in Building template manager for both models. My concern comes when I come to look at the energy consumption for fans in Vista and I get very close values. Does it make sense? I would expect larger difference in the auxiliary energy use. The ventilation ductwork should have quite the same lenght for both models due to their identical floor areas, but the second alternative is a 7 storey building and I would expect it to have higher pressure drop than the first.

These are my results from Vista:
Ap Sys aux + DHW/solar pumps energy: 45.8003 MWh and 45.8101 MWh

I am not quite sure if this has also to do with the energy consumption of the ventilation system (where the difference would be more evident):
Ap Sys heat rej fans/pumps energy: 7.3099 MWh and 14.672 MWh

Does anyone know how ApacheSim is calculating the energy consumption of the fans? Does it take into account the pressure drop of the ductwork? Else what is actually including??

I would really appreciate any comment.
Thank you in advance!

Julian

[PCully]

Hi,

The Air Exchanges won't affect your HVAC system fans, pumps energy use. All the air exchange represents is cool air coming into the building and so adding to heating demand (usually), you can see this by selecting rooms in Vista and viewing the Auxiliary Ventilation gains.

The results you are looking at come from the Apache system only, see the Auxiliary Energy tab on there and you will see they are similar for both buildings (I guess).

Have you had a look at the definitions in the Vista user guide? That might gives you some clues what you are seeing as well.

Phil

[Julian]

Hi Phil,

Thank you for your reply.

I have had a look at the user guides Apache View and Vista. However, they are from an older version of the software I am using now (IESVE 6.3) and are not completely clear to me. I think there have been small changes in how Vista displays results. According to the user guide I should find "System auxiliary energy" under the "Energy" tab in Vista. There is not such result though. The closest option I find is "Ap Sys aux + DHW/solar pumps energy" which I assume is the one I should look at, but I might be wrong.

What I am wondering is what part of the energy consumption of Apache system would correspond to ventilation demand. Is it what I am looking at or am I missing something?

Secondly, I would like to ask wether "Ap Sys heat rej fans/pumps energy" is also a part of the load of the ventilation system or not. Because in the user guide is expresed as Chillers heat rej. pump energy. The fact of not having the same nomenclature in the userguides and in the software is confusing... :/

Thank you for your time.

Julian