# RE: [EnergyPlus_Support] Fancoil total cooling power rate & total water cooling coil power rate

Thanks Richard,

I followed your advised and checked the air enthalpies of all the nodes
involved. Then I realized that the fancoil cooling power rates refer to the
effect of the fancoil on the controlled zone. On the other side, the cooling
coil power rates refer to the energy balance inside the fancoil. As I was
working on an open loop system, there is no relation between this variables.

Finally, I didn't find any documentation about how dehumidification is
managed in a simple cooling coil. I would appreciate if anybody could tell
me.

-----Mensaje original-----
De: Richard J. Liesen [mailto:rliesen@xxxxxxxx]
Enviado el: miércoles, 16 de julio de 2003 18:55
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx; EnergyPlus_Support@yahoogroups.
com
Asunto: Re: [EnergyPlus_Support] Fancoil total cooling power rate & total
water cooling coil power rate

Miguel,
The first thing you need to do is take one of your Fan Coil units and set
the Maximum Outside Air = 0.0 and then look at the reports.  When you do
this then you will see exactly what you expect in the reports, ie. Total >
Sensible, and Total Water Coil Cooling Rate = Fan Coil Total Cooling Rate
+
Fan Power. After you are confident that the variables are reporting what
you expect then add the mixed air stream to the results.  Total Q across
the unit is just the enthalpy change and the sensible Q across the unit is
the change in enthalpy at a constant inlet humidity ratio.

Total Enthalpy
QTotUnitOut = AirMassFlow * (Node(OutletNode)%Enthalpy -
Node(InletNode)%Enthalpy)

Sensible Change
QUnitOut = AirMassFlow *
(PsyHTW(Node(OutletNode)%Temp,Node(InletNode)%HumRat)  &
-
PsyHTW(Node(InletNode)%Temp,Node(InletNode)%HumRat))

Remember that these variables are looking across the entire unit including
the mixed air contributions.

For the example case that I was looking at and when you look at and report
the Temperature and Humidity Ratio at each node location, ie. FanCoil1
#          Description
5,      ZONE1FANCOILAIRINLETNODE
56, ZONE1FANCOILEXHNODE
1,      ZONE1FANCOILOAINNODE
59, ZONE1FANCOILOAMIXEROUTLETNODE
62, ZONE1FANCOILFANOUTLETNODE
65, ZONE1FANCOILCCOUTLETNODE
4,      ZONE1FANCOILAIROUTLETNODE

You will find that the Latent Load added through the mixed air is greater
than what is extracted by the Cooling Coil.

Thanks
Dr. Richard J. Liesen  Ph.D. M.E.
Associate Director, Building Systems Laboratory
Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign
* * * * * * * * * * * * * * * * * * * * * * *

t 02:54 PM 7/16/2003, Miguel Angel Pascual wrote:
>hello,
>
>I'm running a simulation with a FAN COIL UNIT:4 PIPE with a
>COIL:Water:SimpleCooling object and  I have noticed an important
difference
>between the variables "Fancoil total cooling power rate" and  "total
water
>cooling coil power rate". I thought that both variables should be very
>similar, but the difference is much bigger than the electric power fan.
>
>I am taking 100% outside air to the fancoil, and under condensing
conditions
>"Fancoil total cooling power rate" and "Fancoil sensible cooling power
rate"
>are almost the same. In some cases, the total cooling power rate was
smaller
>than the sensible fancoil variables.
>
>Does anybody know what is going on?
>
>
>Miguel Ángel Pascual
>Dtor. Ingeniería
>MIYABI
>mapascual@xxxxxxxxxxxx
>948 203 644
>
>
>
>[Non-text portions of this message have been removed]
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