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Heat Recovery Chiller Autosizing

asked 2016-06-22 18:59:43 -0500

I'm modeling heat recovery from a Chiller:Electric:EIR in EnergyPlus 8.5.0. I'm using the loop configuration from the HeatRecoveryElectricChiller.idf example file with some additional objects for (attempted) autosizing:

Model setup:

  • The chiller heat recovery inlet and outlets nodes are on a branch on the demand side of a heat recovery loop
  • There is a WaterHeater:Mixed on the supply side of the heat recovery loop, connected via the Source inlet and outlet nodes
  • This same WaterHeater:Mixed is on the supply side of my hot water loop, on a branch in parallel with an existing boiler, connected via the Use inlet and outlet nodes.
  • There is a SetpointManager:Scheduled on the supply outlet node of the heat recovery loop set to 95F
  • The Sizing:Plant for the heat recovery loop is set to Heating, with 95F exit and 10F delta-T
  • The heat recovery loop has an PlantEquipmentOperationSchemes listing a PlantEquipmentOperation:HeatingLoad listing the WaterHeater:Mixed for the entire capacity range.

I'm getting zero autosized flow through the heat recovery loop and trying to figure out why.

Here's the link to my idf.

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@jmcneill@Lyle K I've seen your previous questions on related topics. If you've got working IDFs with autosized heat recovery chillers I'd love to see them. Assuming I can figure out the correct configuration, I'll write a Measure to add this in OpenStudio.

aparker gravatar imageaparker ( 2016-06-22 19:02:49 -0500 )edit

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answered 2016-06-23 03:14:57 -0500

Chandan Sharma gravatar image

Looks like EnergyPlus currently allows Design Heat Recovery Water Flow Rate to be autosized for Chiller:Electric:ReformulatedEIR and Chiller:Electric objects only. Though Chiller:Electric:EIR in the Energy+.idd mentions this field as "autosizable", the source code, is missing the below calculations which are in and (only for electric and not other chillers in the modules). In your file, changing the EIR chiller to reformulated EIR gets the E+ to size heat recovery flow rates.

        if ( ElectricChiller( ChillNum ).HeatRecActive ) {
            tmpHeatRecVolFlowRate = ElectricChiller( ChillNum ).Base.CondVolFlowRate * ElectricChiller( ChillNum ).HeatRecCapacityFraction;
            if ( ! ElectricChiller( ChillNum ).DesignHeatRecVolFlowRateWasAutoSized ) tmpHeatRecVolFlowRate = ElectricChiller( ChillNum ).DesignHeatRecVolFlowRate;
            if ( PlantFirstSizesOkayToFinalize ) {
                if ( ElectricChiller( ChillNum ).DesignHeatRecVolFlowRateWasAutoSized ) {
                    ElectricChiller( ChillNum ).DesignHeatRecVolFlowRate = tmpHeatRecVolFlowRate;
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Thanks! Looks like this is a bug in E+ then. @MJWitte can you confirm?

aparker gravatar imageaparker ( 2016-06-23 08:45:02 -0500 )edit
Edwin gravatar imageEdwin ( 2016-06-23 11:55:21 -0500 )edit

@Edwin do you want me to file this?

aparker gravatar imageaparker ( 2016-07-05 10:49:13 -0500 )edit

apartker posted this as a new issue #5765

MJWitte gravatar imageMJWitte ( 2016-09-09 17:16:00 -0500 )edit

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Asked: 2016-06-22 18:59:43 -0500

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Last updated: Jun 23 '16