Re: [EnergyPlus_Support] boiler:simple

[Linda Lawrie <linda@xxxxxxxxxx>]

At 07:14 PM 5/30/2003, zhaicq98 wrote:
>The cooling and heating of my building is provided by a fan coil unit
>in each zone and the cooling plant consists of a electric chiller
>while the heating plant consists of a boiler. When I tried to output
>the energy consumption of this system, I got something confusing.
>
>The theoretical efficiency of my boiler is 0.9 and the fuel use
>coefficents C1, C2 and C3 is 1, 0 and 0 respectively. As I understand
>from the user manual, this kind of input should be modeled as a
>constant efficiency boiler.
>
>I output the FANCOILHEATINGCOIL:Total Water Heating Coil Energy for
>each fan coil unit and sum them up. I also output the Heating:Gas. I
>expect the latter is the former divided by 0.9, which is my boiler
>efficiency, but it is not. In my output, the latter is the former
>divided by 0.34. I would like to know what is going on here.

As always, you can send us or upload the file so we can make a better 
guess.  One of the most knowledgeable of the boiler code had this to say:

>Since we've included thermal mass in the in the water loops, the 
>instantaneous heat transfer rate at the coil isn't the same as the 
>instantaneous heat transfer rate at the boiler.  I'm not a big fan of this 
>approach because it is does give counterintuitive results--everyone 
>assumes that the heat gains/losses in one part of the loop are 
>instantaneously felt in another part of the loop--but it does stabilize 
>the simulation.
>
>On the other hand, there could be a bug in the boiler model.  To check 
>divide HOT WATER LOOP:Plant Loop Heating Demand[W](TimeStep) by the fuel 
>used by the boiler.  This should be a constant 0.9.

Thanks!


Linda

EnergyPlus WebSite: http://www.energyplus.gov
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Member: EnergyPlus Development Team



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