Hello friends,
My name is Mansi Jayswal. I am a final year student of Masters Programme at
CEPT University, India. By profession I am an architect. Currently I am
doing thesis on passive cooling technique (Passive down draught evaporative
cooling system- PDEC ). And try to identified that how much cooling load of
HVAC system can be replaced through this system.
Now my query is that is it eQuest is capable to simulate such building with
wind tower or PHDC (PDEC ) system? If anybody knows please kindly reply. I
have very days left for final submission and I am stuck here.
Thanks
--
Regards,
Mansi,
I doubt you can do this credibly in eQUEST. You really need a CFD type package to be able to simulate this. . A word of caution - the effort to develop the simulation for this is a master's thesis in itself.
Vikram Sami, LEED AP BD+C
Mansi -
We have done some schematic modeling of wind towers with Fluent, a CFD package as noted.
Our climate didn't justify evaporative pre-cooling.
eQUEST has a natural ventilation module, which I have not fully dived into.
I believe it requires inputs that would likely be validated by a CFD model - for example, I don't think eQUEST's natural ventilation model allows for evaporative pre-cooling as a temperature driver for natural air exchange in a space.
As eQUEST models each zone as a fully mixed space, and has limited air transfer between zones, you may also have trouble getting the thermal stratification from eQUEST that would typically be needed to drive natural ventilation in a PDEC.
Aaron Dahlstrom , PE, LEED(r) AP
You may wish to explore the free trial of Design Builder, as it has CFD,
natural ventilation and evaporate cooling.
Tho I am not sure if it can be used for your passive cooling requirement or
not..
Best of luck
I beg to differ on this. eQUEST has an evaporative cooling module. The system that Mansi
describes is essentially a direct evaporative cooler that uses natural forces instead of a
fan to provide the air flow. What I would do using eQUEST would be to model the building
with a direct evaporative cooler at 100% outside air, and play around with the air flow
rates to get a sense of how much cooling loads can be replaced. To go further, you can
also develop a functional equation relating the amount of air flow to the outdoor wind
speed and temperature difference between the evap cooler outlet and the room air
temperature. If you were working with DOE-2.1E, an earlier version of the DOE-2.2 engine
in eQUEST, you could put that in as a FUNCTION, but unfortunately DOE-2.2 doesn't accept
FUNCTIONs.
Joe
Joe Huang
Thank you all for your quick response and Information.
Is it possible that if i use PHDC software to design the PDEC system and
simulate the same building in eQuest ?? PHDC software can give me
the required size of the passive down draught evaporating cooling towers
for the building.
Another option to look into is CoolT developed by Nader Chalfoun at University of Arizona in Tucson. It's a Dos program that is based on empirical data that they collected from the extensive testing they did on Cool Towers (Passive Downdraught Chimneys).
Again - I would throw in words of caution. Passive downdraught chimneys rely on buoyancy driven forces - something that you cannot approximate with a fan driven evaporative cooler or wind driven. eQUEST might be able to model this, but its beyond my knowledge. Also - The folks at UA (Nader Chalfoun & Martin Yoklic) did some testing with cool towers in enclosed spaces. I would try writing to them to get some feedback on issues to consider.
I think Nader is on this list - not sure if he's still active.
Vikram Sami, LEED AP BD+C
Hi Mansi,
CONTAM might help you. http://www.bfrl.nist.gov/IAQanalysis/ It should be
faster to set up a model than CFD.
As Aaron pionted out, eQuest can handle natural ventilation in a single
zone, but that's about it.
Shaun
Shaun Martin LEED AP
Thanks Vikram,
Could you tell me from where i can download this Software " CoolT" ? i
have tried to Google but did not find it anyware. I have even found one of
your research paper. it seems you have already worked on it. it will be
great if you could guide me.
Mansi,
If CoolT is as Vikram describes, this might be the solution to your problem. The main
issue for you is to know the air flow output of the PDEC in actual operations, not under
design conditions, so that other program you mentioned for sizing the PDEC is of little
help. If CoolT is not able to give you air flow rates based on the ambient conditions and
the indoor air temperature, you could try building a simple two-zone model (PDEC,
Building) using CONTAM and then run that stand-alone to get the air flows between the two
zones.
In reference to Vikram's comment, I've said all along that the difference between the PDEC
and a standard DEC
is the mechanism used to drive the air across the media - using natural bouyancy forces in
the first case and a mechanical fan in the second case. Once you have the air flow rate,
the PDEC is actually simpler to model because there's no need to model fan efficiency and
heat gain, etc. In fact, it just takes a single effectiveness curve, or even just a
constant effectiveness number.
Joe
Joe Huang
Dear Mansi,
I am attaching the CoolT program for sizing Passive Downdraft Evaporative Cooling devices. As Vikram said, the program is a dos based and can be run from windows XP. The program calculates temperature drop, water consumption and other important thermodynamic values based on many variables including Pads evaporative cooling efficiency, thickness and area, tower effective height (z), discharge mode (bottom or side) indoor (with screens or outdoor).
The only issue is that it has 8 built-in climate zones. If your climate zone is not included, I have to added and re-compile the program. If your climate zone has somehow close moisture and temperature data than the once included, you can approximate the results.
Good luck with that and let me know if I could be of additional assistance to you.
Cheers,
Nader
Nader V. Chalfoun, Ph.D., LEED? AP, CEA
Since outlook and the university usually blocks any .exe files I have renamed the program CT.txt and you should rename back to CT.exe once you receive it
Nader
-------------------
What is the attached file?
Could you send it as .exe, because it did not translate..
*Jeremiah D. Crossett*
Please don't send EXE files to the mailing list. If you want
to announce that an EXE is available that is fine. Let
people download it or email it directly to them. When EXE's
are sent to the mailing list, I get dozens (maybe hundreds)
of bounce messages as servers reject them.
Thanks,
Jason