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Re: [TRNSYS-users] Chiller and Zones
Nguan,
Again, I must emphasize that I am not an expert on air conditioning
systems, but I can try to give you some advice based on my own experiences
with simulating a chilled water system.
I believe that instead of sizing the chiller based directly on the cooling
load of the building, you should size the device(s) you are using for
transfering cooling power from water to air based on this load. If, for
example, you are using a fan-coil system, the required cooling load will
affect the air flow rate, water flow rate and water temperature needed to
meet the load. Then you can size the chiller based on
m_dot*C_p*(T_water_in-T_water_set), which is the equation for chiller load
(see the documentation).
I would have only one chiller and one (duct based) or several devices (for
example fan coils) to cool the zones. Also make sure that you recalculate
the m_dot ventilation input to zone air change rate (fraction of zone air
mass per hour, 1/h).
Hope this is of some help.
Kind regards,
Knut Erik Enerstvedt
trnsys-users-requ
est@cae.wisc.edu
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Please respond to Subject
trnsys-users@cae. TRNSYS-users Digest, Vol 49, Issue
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----- Message from "#TEO NGUAN TECK#" <Z050128@ntu.edu.sg> on Thu, 8 Jan
2009 15:55:47 +0800 -----
To: <TRNSYS-users@cae.wisc.edu>
Subject: [TRNSYS-users] Chiller and Zones
Hi ALL,
I have obtained the cooling load of my building (based on QCOOL and QLATD)
using idealized cooling in TRNBuild. I have also sized my chiller to meet
the peak load of my model. I am intending to use a single chiller to meet
my model’s cooling demand.
My model consists of 8 zones and the peak load is based on the summation of
the cooling loads from these 8 zones.
I have also created inputs (i.e. RH, Temp, M_dot) to allow my model to
accept the external cooling device, which is a water chiller system. I am
setting the ventilation of all 8 zones to these inputs (i.e. only one
ventilation type).
My query is:
By using a single chiller sized at peak load and setting each zone to
accept the chiller system, would I be oversizing my chiller? Since I
believe each zone’s load is only a fraction of the peak load and my
ventilation type only targets one zone instead of all zones together.
Or, should I be using a chiller for each of my 8 zones (i.e. altogether 8
chillers) and sized them to the respective peak loads of the zones?
PS: My model requires a central core in the middle of the room, so in order
to have the central core, I created 8 zones around it using the Multizone
building.
I hope I am clear with my description.
Any help is deeply appreciated.
Nguan Teck
NTU, Singapore
Final Year Undergrad
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