[BLDG-SIM] Citi Multi Variable Refrigerant System
Tara Frentrop
tstreck at WoodHarbinger.com
Fri Aug 31 10:52:44 PDT 2007
Yes,
Contact Martyn Dodd with EnerySoft for that information.
Tara
________________________________
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Vaibhav
Potnis
Sent: Monday, August 27, 2007 10:27 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Citi Multi Variable Refrigerant System
Is there documentation about how these systems are represented in
EnergyPro?
Vaibhav Potnis
www.greenbuildingservices.com
________________________________
From: "Tara Frentrop" <tstreck at WoodHarbinger.com>
Reply-To: tstreck at WoodHarbinger.com
To: <BLDG-SIM at gard.com>
Subject: [BLDG-SIM] Citi Multi Variable Refrigerant System
Date: Wed, 22 Aug 2007 12:28:42 -0700
Dana,
A model has been created which can simulate Mitsubishi City
Multi. It is called EnergyPro and was developed by Energy Soft. Their
web address is:
http://www.energysoft.com/
Tara Frentrop
Mechanical Engineer
LEED Accredited Professional
Wood Harbinger, Inc.
Mechanical/Electrical Engineers
3009 112th Ave NE, Ste 100
Bellevue, WA 98004-8008
(425) 822-9499
(425) 822-4338 Fax
tstreck at woodharbinger.com
www.woodharbinger.com
________________________________
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of
Dana Troy
Sent: Wednesday, August 22, 2007 11:41 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Citi Multi Variable Refrigerant System
Hello again,
I recieved some great information from Sam Mason who is an
environmental designer at Atelier Ten Consulting Environmental Designers
in New York. He researched the City Multi for his Masters. Thank you Sam
for your help!
Here it is:
Dana,
The City Multi was the topic of my master's project and I ran
into several
problems trying to the model the system. My conclusion was that
using eQUEST, it is not possible to model the system for a few
reasons.
There is also a lack of information from Mitsubishi that makes
modeling
tough.
First, with regards to each indoor unit, setting a constant EIR
(like
you mentioned doing) does not allow for the variation in
performance due
to temperature changes in the space and outdoors. If you look in
the
engineering manual, there are power and capacity relations for
each unit
at various temperatures. These corrections need to be
incorporated for
each indoor unit and this may be possible using ms-dos batch
files.
Second, there is no way to account for the free-energy BC
controller
operation in terms of refrigerant transferred to/from zones and
the
effectiveness at which the refrigerant used. Even though the
coil loads
would be known for each zone from DOE2, the state and
temperature of the
refrigerant would be needed to figure out how much energy is
available
fro space conditioning in other zones.
Third, DOE2 is steady-state modeling software, but this system
is hugely
dynamic. From my monitoring of the system, I found that the
compressor
cycles at various frequencies over the course of one minute,
thus
changing the capacity of the system hundreds of times an hour.
Energy
Plus might be a better tool because it can run at 15 minute
intervals.
Fourth, Mitsubishi does not supply the part load curves for the
compressor operation. This means there is no way to accurately
model
the unloading and part load performance of the compressor. In
addition,
it is an inverter driven and not a hard start compressor, so the
part
load performance should be quite good.
These systems are going to become
more popular and already are in certain areas. I have found one
paper
referring to a module for energy plus that models these types of
systems, but I cannot get a hold of the author. I also know that
energy
soft has been working on developing a module for their software,
but I
do not know the status.
Sam
--
Sam Mason
Environmental Designer
Atelier Ten
Consulting Environmental Designers
45 East 20th Street, 4th Floor
New York, NY 10003
T +1 (212) 254-4500
F +1 (212) 254-1259
E sam.mason at atelierten.com
W www.atelierten.com
-----Original Message-----
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com]On
Behalf Of Dana Troy
Sent: Wednesday, August 22, 2007 8:29 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Citi Multi Variable Refrigerant
System
Hello all,
We have recently performed an analysis on a building
that is potentially going to incorporate the City Multi system. After
many hours of going through eQUEST, I devised a method of modeling it
that I would like to run past you all for any thoughts/ideas.
First, for those not aware of the problems, here is a
background of the systems:
The City Multi system consists of essentially three
parts: the condenser, the BC controller, and the heat exchanger unit at
each zone. Refrigerant is the only property used for heat exchange, i.e.
there is no water running from the condenser to the controller to the
zone units. Each zone unit is essentially a fan coil, in that there is
no compressor work at the zone, only fan energy. The BC controller is
essentially a heat exchanger which gives the City Multi system a large
advantage by being able to transfer heat, say from the south face of a
building, to the north face, which is in the shade. All of the
individual zone units connect to the BC controller and the BC controller
distributes the refrigerant accordingly. If there is not enough free
energy being generated by the system, the compressor kicks in and
supplies or rejects heat from the loop to meet the demand.
To model this in eQUEST, which has been suggested
before, the water source heat pump system should be selected in order to
account for the free transfer of heat from zone to zone. There are,
however, several problems with this. One is that pumping energy is
required to pump the water throughout the building. The second problem
is that at each zone, each heat pump runs a compression cycle in order
to supply or reject heat to or from the zone to the water loop. The
third is that a boiler and cooling tower take the place for the
condenser in the City Multi system. Each system requires a make-up air
unit which can be modeled the same in each simulation.
Now here is what I would like you all to review:
These are some of the steps I went to in order to make
the water source heat pump as much like the City Multi as possible.
* Made the boiler and electric boiler (to simulate
the electric compressor) and gave it the appropriate heating EIR that
was specified in the Citi Multi specification manual. I gave the fan the
same EIR as the cooling side of the compressor in the same manual.
* I made a spreadsheet to subtract out the pumping
energy (only from the water loop! Not the DHW loop!) to simulate the
suction of the refrigerant through the building in the City Multi
system. I had to do this in the BEPS and the BEPU report which made it
kind of a hassle to find the energy cost savings.
* For each heat pump, I set the EIR equal to
0.0001 to simulate the fan coil in the City Multi system. Therefore,
whatever heat is transferred to or from the water loop is only shown
with the fan energy from blowing the air over the coils. IF this is not
a proper way to do it, then what should the EIR be? It cannot be the EIR
from the condenser, because that has nothing to do with the free heat
transfer energy at the zones.
What do you guys think about this approach? I figure
that since this is a tough problem that other people have encountered as
well, I might as well use this huge resource that has many great minds
to come to a solution.
Please, any feedback would be greatly appreciated.
Regards,
Dana Troy
Energy Analyst
<http://www.glumac.com/>
________________________________
320 SW Washington, Suite 200
Portland, OR 97204-2640
T. 503.227.5280 F. 503.274.7674
D. 503.345.6286
Thinking. Inside the building.
www.glumac.com <http://www.glumac.com/>
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