No Change in Zone Air Relative Humidity When Modifying Rated RH in AirChiller Object
Hello,
I am working on a modeling project in EnergyPlus for a refrigerated warehouse and I’m having trouble with the airchiller object used to model the evaporators. I’d really appreciate any insights or explanations from the community about this issue.
Context:
Here’s the setup I’m working with:
- Object Used: AirChiller
- Type: EuropeanSC3NominalWet
- Rated Cooling Capacity: 70 kW
- Cold Room Setpoint: -18°C ±1°C
- Rated Evaporating Temperature: -25°C
- Temperature Difference (DT1): 7 K
- Infiltration/Interzone Exchange: None
- Internal Loads: Only lighting and evaporators fan
Problem Description:
I’ve been experimenting with the AirChiller object by changing the rated relative humidity (RH) to observe its impact on the zone air RH. Initially, I set the rated RH to 95%, and the zone air RH fluctuated between 82% and 100%. When I changed the rated RH to 50%, I expected the zone air RH to approach this value, but I observed no change in the zone air RH, which still fluctuated between 82% and 100%.
Upon reviewing the EnergyPlus source code, I found that the zone RH is calculated as follows:
// Zone relative humidity (%)
Real64 ZoneRHPercent = Psychrometrics::PsyRhFnTdbWPb(state,
state.dataLoopNodes->Node(this->ZoneNodeNum).Temp,
state.dataLoopNodes->Node(this->ZoneNodeNum).HumRat,
state.dataEnvrn->OutBaroPress) * 100.0;
However, I couldn’t find where the rated RH input in the AirChiller object is used in the calculations. Can anyone explain why changing the rated RH has no effect on the zone air RH? Is there a specific setting or configuration I might be missing, or is the rated RH not directly linked to the zone RH in this model?
Any insights or suggestions would be greatly appreciated!
Thank you,
I’m using EnergyPlus 9.2 for co-simulation with MATLAB reasons, but these results are from standalone EnergyPlus runs.
