|
Hi Vikram,
The latest release of EnergyPlus (v. 1.1.1) added a model for
light pipes, i.e. tubular daylighting devices. The model is fully
described in the documentation that comes with the program.
Just to give you an
idea in brief, light pipes can add both solar gains and conductive/convective
gains to the space below. The solar gains are calculated by analyzing the
multiple internal reflections of the incident beam, sky, and
ground radiation entering the pipe. The amount of radiation
transmitted depends on the incident angle, reflectivity, and geometry of the
pipe, and on the properties of the glazing at either end of the pipe.
Fortunately, all of this is entirely handled by the program.
The conductive/convective gains, on the other
hand, require the user to enter an effective thermal
resistance (R-value) between the top and bottom of the light pipe. The
problem is knowing what R-value to use. Very little research has
been done on this area of the problem (as of about 1 year ago--the last time I
looked). I have only found one paper that analyzes the
conductive/convective behavior of light pipes:
Harrison, S. J., McCurdy, G.
G., Cooke, R. "Preliminary Evaluation of the Daylighting and Thermal
Performance of Cylindrical Skylights", Proceedings of International Daylight
Conference, Ottawa, Canada, 1998, pp. 205-212.
They
report an
average thermal resistance of 0.279 m2 K/W for a pipe measuring 1.83 m by 0.33
m.
Hope this
helps!
Peter Graham
Ellis
National Renewable
Energy Laboratory
Center for Buildings
and Thermal Systems
1617 Cole
Boulevard
Golden, Colorado
80401-3393
303-384-7443
-----Original Message-----
From: Vikram Sami [mailto:Vikram@xxxxxxxxxxxxxx] Sent: Wednesday, January 21, 2004 4:04 PM To: BLDG-SIM@xxxxxxxx Subject: [BLDG-SIM] Heat gain from light pipes Hi,
I have a question about light
pipes. We are using then for a project, and I was wondering if there was
any way to calculate the heat transmitted to the space below through the
pipes.
Thanks
Vikram Sami =====================================================You received this e-mail because you are subscribed to the BLDG-SIM@xxxxxxxx mailing list. To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE@xxxxxxxx =====================================================You received this e-mail because you are subscribed to the BLDG-SIM@xxxxxxxx mailing list. To unsubscribe from this mailing list send a blank message to BLDG-SIM-UNSUBSCRIBE@xxxxxxxx |