You need to adjust your thinking to the simulation world. The zone sees that it receives a supplied air at said conditions (from a window or from a supply diffuser or both). It doesn't care where that air comes from.
That being said, I think you are right in the sense that the system must combat both latent and sensible loads, which in your case should be equal.
I suggest using a text editor to compare your files (expidf) to make sure the other fields are the same for all the other objects.
As a side note:
The mechanical system that delivers the air at said conditions, consumes energy (or not) to do that. For example, that system takes in a predifined outdoor air amount of cold outdoor air and needs to reheat it and humidify it (humidifiers eat energy) to bring it to your defined supply air conditions.
In your case A, you have a recirculation system. Depending on moisture loads from persons in the zone, the idealLoadshvac system may need to cool the extract air past the due point temperature to dehumidify and then reheat the air to the supply temp.
In case B, the window air is cold and causes drafts as it is not reheated as such. As the wellmixed zone simply mixes it in, this aspect is not considered by the program and the well mixed zone air temp seems fine. The mechanical system inserts enough warm air at preset condition to combate any loads that come from the cold air. The infiltration will however reduce the moisture content in the extract air.
Dear Kamran,
Dear Jean,
I guess as I am not a mechanical engineer but an architect, I don't quite understand you.
Kamran, I am not quite sure. But I guess as this system works at 100% efficiency, what you say is not the case. Am I right?
Jean, the humidity and the temperature that we specify in this objects belong to supply air. I think, when we set the system to provide a specific amount of outdoor air (optionally in another fields), this amount of air should be simply the outdoor air and not a conditioned air. What do you think?
Best,
Farhang
Univ. Ass. M.Sc. Farhang Tahmasebi
Department of Building Physics and Building Ecology
Vienna University of Technology
---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <jeannieboef@...> wrote:Air entering conditions (humidity and temp) are user defined for the idealloadshvac system.Window air is based on ODA conditions.Therefore the airloads from entering air are different.Mit freundlichen Grü�en- Sent from my iPhone (excuse the brevity)i. A.Jean Maraisb.i.g. bechtoldTel. +49 30 6706662-23On 14.01.2014, at 14:59, <farhang.tahmasebi@...> wrote:Hi,
Using HVACTemplate:Zone:IdealLoadsAirSystem object in EnergyPlus 8.1.0, I compared the Zone Ideal Loads Supply Air Sensible Heating Energy in 2 models:A) With an ideal load system, with no outdoor air provided by system, and an infiltration of 0.01 m3/sB) With an ideal load system with 0.01 m3/s outdoor air provided by system, no heat recovery, no economizer and no infiltration.However, despite the equal amount of outdoor air provided, the Zone Ideal Loads Supply Air Sensible Heating Energy in model B is 27% lower that model A. Does it make sense?I found out that the average amount of outdoor air that comes actually to the zone (based on the outputs) is 0.0104 m3/s in model A and 0.0102 m3/s in model B. But this difference can not explain that 27% relative deviation.Can somebody explain this? Does it make a difference that we bring the outdoor air via windows or a mechanical system without heat recovery?Regards,FarhangUniv. Ass. M.Sc. Farhang Tahmasebi
Department of Building Physics and Building Ecology
Vienna University of Technology
Karlsplatz 13, 1040 Vienna, Austria
e-mail: farhang.tahmasebi@...
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