Correction of Some Problems in the ChillerHeater Model

[RKStrand]

Pull request overview

• Fixes CentralHeatPumpSystem / ChillerHeater Misbehavior #10065 and CentralHeatPumpSystem-CentralChillerHeaterSystem_Cooling_Heating.idf #7838
• Changes were made to the ChillerHeater model to correct some issues that users noted. First, when in heating mode or heating dominant mode, the evaporator heat flow and compressor power consumption were always fixed at maximum PLR and thus the evaporator and compressor sum would be higher than the condenser heat flow. This was traced back to a bug in the algorithm for when the ChillerHeater was in that mode where when the condenser heat transfer was reduced the evaporator heat transfer and compressor power were never reduced accordingly. This has been corrected. Second, when there were cases where when in simultaneous heating and cooling mode that zero electric consumption from the compressor was being reported despite there being heat transfer at both the evaporator and condenser. This was traced back to a problem in a key logic decision in the ChillerHeater code that caused the compressor energy to be left at zero and the condenser to not be simulated when in heat recovery mode when heating was dominant. These issues along with a few other improvements in some parts of the algorithm and making the code much easier to read were made and 5 new unit tests were added to exercise new subroutines that were added as part of the code improvements. Differences in the output were noted only for the two files that have ChillerHeaters in the file and this was expected because of the fixes to the problems noted above.

NOTE: ENHANCEMENTS MUST FOLLOW A SUBMISSION PROCESS INCLUDING A FEATURE PROPOSAL AND DESIGN DOCUMENT PRIOR TO SUBMITTING CODE

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[RKStrand]

@Myoldmopar @mjwitte Ok, this is a significant improvement over what we had before. I think that the bugs noted by the users previously have been fixed now. Not saying that this model is without problems but this should be a good step forward. Let me know if you have any questions or concerns.

[RKStrand]

Graphs showing fix of evaporator/compressor always at full power when they should not be (this is for control mode 2--heating only):

[Myoldmopar]

This looks fine to me. Good testing and description of the issue and changes. And good improvement just for a few dozen lines of code. I'm happy with this.

[Myoldmopar]

And CI has just the expected diffs in two files, otherwise clean. I'm inclined to merge, anyone have any issues here?

[rraustad]

No issues. It looks much better than before.

[Myoldmopar]

Great, this is clean and ready! Thanks @RKStrand and @rraustad