Re: [EnergyPlus_Support] RE: Natural vs. mechanical ventilation

On Tue, Jan 14, 2014 at 7:04 PM, <farhang.tahmasebi@xxxxxxxxx> wrote:

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 Grüßen- Sent from my iPhone (excuse the brevity)

i. A.
Jean Marais
b.i.g. bechtold
Tel. +49 30 6706662-23

On 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/s

B) 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,
Farhang

Univ. 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@...

Kamran Naeiji

PhD. Student
Technische Universität Berlin
Faculty VI Planning Building Environment

Chair Design and Structure

Secretariat A 16

Straße des 17. Juni 152,

D-10623 Berlin

Tel.: +49 (0)30 314-21483

Fax: +49 (0)30314-21844

Re: [EnergyPlus_Support] RE: Natural vs. mechanical ventilation - difference in heating loads