Re: [EnergyPlus_Support] Problems on Cooling load demand in condenser loop

["Michael J. Witte" <mjwitte@xxxxxxxx>]

It appears that there was never a response to this message.  My apologies for 
the very delayed response.  

When checking the energy balance on a loop, it is not always valid to sum up 
the report variables "Plant Loop Cooling Demand" and "Plant Loop Heating 
Demand".  These variables represent the required heating or cooling to bring a 
loop to its setpoint for a given timestep.  If the loop does not land exactly 
at its setpoint, then the loop demand for the next timestep will include the 
remaining load not met in the previous timestep.

To compare the energy flow in and out of a loop, it is better to sum up the 
heat transfer of the individual components on the loop and remember to include 
the Pump Heat To Fluid Energy.  If you still are unable to show a balance, 
please upload your input file to the yahoo files area or send it as a zipped 
attachment to energyplus-support@xxxxxxxx

Mike


On 4 Jul 2004, at 16:30, ekwtsang wrote:

> Dear all,
> I have modelled a building with two different condensing water 
> plants. The first one uses cooling tower only connected to electric 
> chillers. The second one uses cooling tower serves the electric 
> chillers plus a ground source heat pump at demand side.
> 
> Generally when i check the cooling demand, the sum of source side 
> heat transfer rate of heat pump and the cooling demand of the 
> condensing water loop of the second arragement is nearly the same as 
> the total cooling demand from the first one in condensing water loop.
> 
> However, when i sum up all heat transfer of the cooling tower in the 
> plant that with heat pump, it is found that the total heat transfer 
> in cooling tower < cooling load demand for the condenser plant loop. 
> Which it does not happen in the first one (condensing plant without 
> heat pump)(total heat transfer in cooling tower nearly the same as 
> the cooling load demand for the condenser plant loop). Also when i 
> check the outlet temperature for both plants, it is found that both 
> of them are at my setpoint temperature.
> 
> I want to ask do these results correct or any protential problem 
> with such arrangement?
> 
> Regards,
> Ernest Tsang
> 
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 



========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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