Closed mwetter closed 2 years ago
The development branch is issue101_caseStudyFullHVAC_sizingDataVAV
.
Todo
50, !- Maximum Heating Supply Air Temperature {C}
but we use 45 degC as the maximum heating water temperature. The 50 degC should likely be reduced, and then the Modelica sizing data be updated accordingly (see THeaDisVAV_nominal
, THeaWatSup_nominal
and THeaWatRet_nominal
).
conAHU
, tab "Supply Air Temperature", group "Temperature limits".Note that the heating water temperatures and heating air flow rates at design conditions need to be changed. With 45/35C, we get
Error: The following error was detected at time: 0
eps_nominal out of bounds, eps_nominal = 1.87907
To achieve the required heat transfer rate at epsilon=0.8, set |T_a1_nominal-T_a2_nominal| = 75.1628
or increase flow rates. The current parameters result in
CMin_flow_nominal = 339.181
CMax_flow_nominal = 2039.5
Failed condition: vav.VAVBox[1].terHea.eps_nominal > 0 and vav.VAVBox[1].terHea.eps_nominal < 1
FixInitials:Init: Integrator failed to start model.
E.g., for the air and water flow rates from EnergyPlus, we would need 75K temperature difference between heating water supply and air inlet temperature.
@yanchenpnnl: There seems to be something wrong with the flow rates from EnergyPlus. I transferred them to issue101_caseStudyFullHVAC_sizingDataVAV
, commit cb1238d8a8f19d6c0f79020a6faff08e5be268ef.
The terminal box computes eps_nominal = QHea_nominal/( CMin_flow * dT_nominal)
where dT_nominal
is the design temperature difference of the inlets. With this, the modeI gets eps_nominal = 1.87907
which is not physical, and the model stops after initialization due to an assert that checks for eps_nominal
. Can you please verify what heat exchanger efficiencies result from the EnergyPlus design calculations with 45/35C heating temperatures, and 13 degC AHU discharge temperature. The above error indicates that we would need 13+75=88 C heating water temperature to have a heat exchanger effectiveness of 0.8. Note that CMin_flow_nominal
is from medium 2, which is the air-side.
All updated sizes are in SizingParameter.mo
.
This issue is to add to the branch
issue92_caseStudyFullHVAC
the sizing data from the EnergyPlus simulations.