Warnings When Modeling Walk-in Freezer Using Air-Chiller Object - Internal Temperature Fluctuations
Hello everyone,
I am currently working on modeling a walk-in freezer using the air-chiller object and have encountered some warnings that I am struggling to understand and resolve.
IDF file is accessible here: IDF file
I use E+V9.2 you can find it here
Here are the key points of my model:
- Objective: I am attempting to model
a walk-in freezer using the
air-chiller object.
- Setpoint: The walk-in setpoint is
-22°C ± 2K. To account for internal temperature fluctuations, I have
used the "Temperature difference
between cutout and setpoint"
approach, setting the temperature at
-18°C and the cutout at 2K.
- Material Construction: I have
utilized Polystyrene High Density as
the construction material with a
thickness of 0.2m and a thermal
conductivity of 0.036 W/m.K.
- Defrost Cycles: Three defrost cycles
are defined in the model.
The figure below plots the internal temperature fluctuations over a 3-hour period. it can be seen the the fluctautions exhibit a high frequency.
Upon checking the error and warning file, I found some warnings, but I am unsure about their causes.
The warnings (File.err):
EnergyPlus V9.2
Program Version,EnergyPlus, Version 9.2.0-921312fa1d, YMD=2024.01.02 15:58,
** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR NTZ136-9B" unused.
YMD=2024.01.05 15:54,
** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR NTZ108-9B" unused.
** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR VTZ038-G" unused.
************* Testing Individual Branch Integrity
************* All Branches passed integrity testing
************* Testing Individual Supply Air Path Integrity
************* All Supply Air Paths passed integrity testing
************* Testing Individual Return Air Path Integrity
************* All Return Air Paths passed integrity testing
************* No node connection errors were found.
************* Beginning Simulation
** Warning ** Zone Air Heat Balance is out of balance for zone named WALK-IN ZONE
** ~~~ ** Zone Air Heat Balance Deviation Rate is more than 154.6 163.7 {W}
** ~~~ ** Occurrence info: Environment=RUN PERIOD, at Simulation time=08/10 00:02 00:00 - 00:03
00:01
************* Simulation Error Summary *************
** Warning ** The following fluid names are "Unused Fluids". These fluids are in the idf
** ~~~ ** file but are never obtained by the simulation and therefore are NOT used.
************* Refrigerant=NH3
** Warning ** The following schedule names are "Unused Schedules". These schedules are in the idf
** ~~~ ** file but are never obtained by the simulation and therefore are NOT used.
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=ZONE CONTROL TYPE DUAL SET POINT SCHED.
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=WORK EFF. SCHEDULE
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=REF SYSTEM WORK SCH
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=ZONE CONTROL TYPE SCHED DUAL YEARROUND
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=NO DEFROSTSCHED
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=NO DRIPDOWNSCHED
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=INFILTRATIONSCHEDULE
*************
************* ===== Recurring Error Summary =====
************* The following recurring error messages occurred.
*************
************* ** Warning ** Refrigeration:System chilling WarehouseCoils WALK-IN LOWTEMPSYSTEM - Refrigeration system unable to meet load of warehouse coils chilled by system ... continues by derating coil load
************* ** ~~~ ** This error occurred 99 25 total times;
************* ** ~~~ ** during Warmup 93 25 times;
************* ** ~~~ ** during Sizing 0 times.
*************
************* ** Warning ** Zone Air Heat Balance is out of balance ... zone named WALK-IN ZONE
************* ** ~~~ ** This error occurred 656 553 total times;
************* ** ~~~ ** during Warmup 0 times;
************* ** ~~~ ** during Sizing 0 times.
************* ** ~~~ ** Max=2776.636668 Max=3737.796328 {W} Min=2.026235E-002 Min=2.899823E-002 {W}
*************
*************
************* ===== Final Error Summary =====
************* The following error categories occurred. Consider correcting or noting.
************* Zone Air Heat Balance Warnings
************* ..Zone Air Heat Balance out of Balance warnings are currently used by developers.
************* ..Users can safely ignore these warnings.
*************
************* EnergyPlus Warmup Error Summary. During Warmup: 0 Warning; 0 Severe Errors.
************* EnergyPlus Sizing Error Summary. During Sizing: 0 Warning; 0 Severe Errors.
************* EnergyPlus Completed Successfully-- 759 582 Warning; 0 Severe Errors; Elapsed Time=00hr 00min 6.72sec
6.28sec
EnergyPlus V23.2
Program Version,EnergyPlus, Version 23.2.0-7636e6b3e9, YMD=2024.01.05 15:55,
** Warning ** CheckEnvironmentSpecifications: SimulationControl specified doing design day simulations, but no design environments specified.
** ~~~ ** ...No design environment results produced. For these results, add appropriate SizingPeriod:* objects for your simulation.
** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR NTZ108-9B" unused.
** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR VTZ038-G" unused.
************* Testing Individual Branch Integrity
************* All Branches passed integrity testing
************* Testing Individual Supply Air Path Integrity
************* All Supply Air Paths passed integrity testing
************* Testing Individual Return Air Path Integrity
************* All Return Air Paths passed integrity testing
************* No node connection errors were found.
************* Beginning Simulation
** Warning ** Zone Air Heat Balance is out of balance for zone named WALK-IN ZONE
** ~~~ ** Zone Air Heat Balance Deviation Rate is more than 204.7 {W}
** ~~~ ** Occurrence info: Environment=RUN PERIOD, at Simulation time=08/10 00:01 - 00:02
************* Simulation Error Summary *************
** Warning ** The following lines are "Unused Objects". These objects are in the input
** ~~~ ** file but are never obtained by the simulation and therefore are NOT used.
** ~~~ ** Each unused object is shown.
** ~~~ ** See InputOutputReference document for more details.
************* Object=HeatBalanceSettings:ConductionFiniteDifference=HeatBalanceSettings:ConductionFiniteDifference 1
** Warning ** The following fluid names are "Unused Fluids". These fluids are in the idf
** ~~~ ** file but are never obtained by the simulation and therefore are NOT used.
************* Refrigerant=NH3
** Warning ** The following schedule names are "Unused Schedules". These schedules are in the idf
** ~~~ ** file but are never obtained by the simulation and therefore are NOT used.
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=ZONE CONTROL TYPE DUAL SET POINT SCHED.
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=WORK EFF. SCHEDULE
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=REF SYSTEM WORK SCH
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=ZONE CONTROL TYPE SCHED DUAL YEARROUND
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=NO DEFROSTSCHED
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=NO DRIPDOWNSCHED
************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=INFILTRATIONSCHEDULE
*************
************* ===== Recurring Error Summary =====
************* The following recurring error messages occurred.
*************
************* ** Warning ** Refrigeration:System chilling WarehouseCoils WALK-IN LOWTEMPSYSTEM - Refrigeration system unable to meet load of warehouse coils chilled by system ... continues by derating coil load
************* ** ~~~ ** This error occurred 25 total times;
************* ** ~~~ ** during Warmup 25 times;
************* ** ~~~ ** during Sizing 0 times.
*************
************* ** Warning ** Zone Air Heat Balance is out of balance ... zone named WALK-IN ZONE
************* ** ~~~ ** This error occurred 495 total times;
************* ** ~~~ ** during Warmup 0 times;
************* ** ~~~ ** during Sizing 0 times.
************* ** ~~~ ** Max=2894.112149 {W} Min=1.764212 {W}
*************
*************
************* ===== Final Error Summary =====
************* The following error categories occurred. Consider correcting or noting.
************* Zone Air Heat Balance Warnings
************* ..Zone Air Heat Balance out of Balance warnings are currently used by developers.
************* ..Users can safely ignore these warnings.
*************
************* EnergyPlus Warmup Error Summary. During Warmup: 0 Warning; 0 Severe Errors.
************* EnergyPlus Sizing Error Summary. During Sizing: 0 Warning; 0 Severe Errors.
************* EnergyPlus Completed Successfully-- 526 Warning; 0 Severe Errors; Elapsed Time=00hr 00min 0.92sec
I am uncertain about the cause of these warnings and how they might be contributing to the observed temperature fluctuations. I would greatly appreciate it if someone could explain why these warnings are occurring and provide insights on how to resolve them.
Thank you in advance for your time and assistance.
Best regards,
