Hi, Xing
Zone Total Internal Heat Gain [J] probably included the latent heat gain. Zone Window Heat Gain [W] can be as high as 1000 watt/m2 of window area.
If there is no partition in the building, part of the solar beam power can enter one window and leave the other sindows.
If the 5000m2 is for one ground floor, the building surface ground temperature would be low. (35m from the eadge to the center of the building.) NanJing in Summer would be about 22°C or less.
If the building is comfortable with natural ventilatin in Summer, the HVAC power is zero. Therefore, 25.9 w/m2 is typical and not low. (75 kW or 25kW electrical power unit is quite a large cooling unit.)
The window heat gain can be reducec by external shading. The internal heat gain can be removed by venting the plenum and attic area.
Use as much as possible of natural lighting during the day.
That was the reason why I said that the LEED and ASHRAE comfort model need not be followed. If the building follows the New York style, then HVAC etc. will be needed.
EPlus is very useful to verify the effectiveness of the external shading, orientation of the windows, and the amount of insulation between the ceiling and the roof, and the cool roof design.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: xing.shi.2006@xxxxxxxxx
Date: Sun, 14 Aug 2011 09:05:05 +0000
Subject: [EnergyPlus_Support] Different zone cooling load???
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Zone Total Internal Heat Gain [J] probably included the latent heat gain. Zone Window Heat Gain [W] can be as high as 1000 watt/m2 of window area.
If there is no partition in the building, part of the solar beam power can enter one window and leave the other sindows.
If the 5000m2 is for one ground floor, the building surface ground temperature would be low. (35m from the eadge to the center of the building.) NanJing in Summer would be about 22°C or less.
If the building is comfortable with natural ventilatin in Summer, the HVAC power is zero. Therefore, 25.9 w/m2 is typical and not low. (75 kW or 25kW electrical power unit is quite a large cooling unit.)
The window heat gain can be reducec by external shading. The internal heat gain can be removed by venting the plenum and attic area.
Use as much as possible of natural lighting during the day.
That was the reason why I said that the LEED and ASHRAE comfort model need not be followed. If the building follows the New York style, then HVAC etc. will be needed.
EPlus is very useful to verify the effectiveness of the external shading, orientation of the windows, and the amount of insulation between the ceiling and the roof, and the cool roof design.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: xing.shi.2006@xxxxxxxxx
Date: Sun, 14 Aug 2011 09:05:05 +0000
Subject: [EnergyPlus_Support] Different zone cooling load???
We used the web-based example file generator to obtain an IDF file for System 8 (VAV + PFP boxes) and used the weather file of Nanjing, China. In HVACSizingSummary, we found the calculated zone cooling load is 129523 W. The specified design day is July 21.
We then opened the CSV file and added Zone Total Internal Heat Gain [J] (divided by 3600 to get Watts) to Zone Window Heat Gain [W]. Surprisingly, the largest number is 184643, much larger than 129523.
How could this happen? We did not even include heat gain through the opaque envelope and others.
By the way, the conditioned area is a little more than 5000 m2, giving a cooling load of 25.9 W/m2 (129523 divided by 5000). This seems to be too low. Is there anything wrong?
Thank you!
We then opened the CSV file and added Zone Total Internal Heat Gain [J] (divided by 3600 to get Watts) to Zone Window Heat Gain [W]. Surprisingly, the largest number is 184643, much larger than 129523.
How could this happen? We did not even include heat gain through the opaque envelope and others.
By the way, the conditioned area is a little more than 5000 m2, giving a cooling load of 25.9 W/m2 (129523 divided by 5000). This seems to be too low. Is there anything wrong?
Thank you!
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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