RE: [EnergyPlus_Support] Flow rate problem of domestic hot water

["Griffith, Brent" <brent_griffith@xxxxxxxx>]

Hi, 

 

The autosizing routines are only looking at the thermal loads on the
zone and are not quite smart enough to also factor in the added loads
from domestic hot water.   You'll have to manually size the pump and
plant loop design flow rate.   You can find the value by taking the
autosizing's flow rate result (reported in the eio) and then manually
add the additional flow rate for the domestic hot water.    

 

For a constant flow pump, you will also need a third bypass that is in
parallel with the coil and domestic hot water. 

 

Brent

 

  _____  

From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of energypluser
Sent: Tuesday, July 11, 2006 11:58 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Flow rate problem of domestic hot water

 

Dear all

I set a domestic hot water object that is parallel to a fan coil unit.
These two object are 
served by a water heater. And I set the flow rate of the domestic water
object equals to 
0.001m3/s. While I use the autosizing function of EnergyPlus to size the
fan coil unit, I 
find that the maximum flow rate of the plant loop is equal to the amount
of the fan coil 
unit rather than that of the domestic water in the EIO file. Since that
the flow rate of the 
fan coil unit is less than that of the domestic water, I wonder why
EnergyPlus does not use 
the flow rate of the domestic water. During the simulation, I use a
variable speed pump, 
and the autosizing result of the pump flow rate is equal to that of the
fan coil unit. When I 
changed the pump type into constant speed, and set the flow rate of the
pump equal to 
that of the domestic water, EnergyPlus showed warnings about that the
flow resolver is 
unable to calculate the flow rate correctly.The warning said that the
upper limit of the flow 
rate is equal to the flow rate of the fan coil unit, and the flow rate
of the constant speed 
pump is bigger than that of the fan coil unit.
I want to set a bigger flow rate for the plant loop in order to increase
the heating demand 
of the domestic water. Since the temperature difference of the water
mixer is around 8C, I 
can not make the heating demand of the domestic water big enough based
on the flow 
rate of the fan coil unit.
How can I fixed these problems?
Thank you in advance.

mac.cz

 



[Non-text portions of this message have been removed]



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