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Re: [EnergyPlus_Support] Re: Fwd: Central Heat Production vs terminal units

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Re: Fwd: Central Heat Production vs terminal units
From: Richard Raustad <RRaustad@xxxxxxxxxxxx>
Date: Fri, 29 Aug 2008 14:32:34 -0400
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Yes, if the air temperature entering the heat pump water heater is 5C, 
then the heat pump's DX cooling coil will likely freeze. Is your heat 
pump water heater outdoors? It would typically be located in a 
mechanical room, storage room, or other similar type of space.

anarui.oliveira wrote:
>
> Temperatures below 5ºC have npo reason to cause that kind of
> behaviour, have they?
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> <mailto:EnergyPlus_Support%40yahoogroups.com>, "anarui.oliveira"
> <anarui.oliveira@...> wrote:
> >
> > Thanks.
> > I based my adpated model on that Example File, and I've checked
> again
> > now... I think that node connections and the like are correct...
> > I get some warnings about freezing possibility, but other than
> that,
> > it seems OK... except that the Heat Pump DX Coil gives a lot more
> > energy than is being used by the demand side coils.
> > I'll keep trying to find out the bug, I guess...
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > <RRaustad@> wrote:
> > >
> > > Look at the example file HeatPumpWaterHeater.idf. In your file,
> > hook up
> > > the plant loop to the USE SIDE nodes in the WaterHeater:Mixed
> > object.
> > > Just use a 1 for the use side effectiveness value.
> > >
> > > HEAT PUMP:WATER HEATER,
> > > Zone5HeatPumpWaterHeater,!- Heat Pump Name
> > > HeatPumpWaterHeaterSch, !- Availability Schedule Name
> > > HPWHTempSch, !- Heat Pump Compressor Set Point
> > > Temperature Schedule Name
> > > 2.0, !- Dead Band Temperature Difference
> > {deltaC}
> > > HPWHWaterInletNode, !- Condenser Water Inlet Node Name
> > > HPWHWaterOutletNode, !- Condenser Water Outlet Node Name
> > > autocalculate, !- Condenser Water Volumetric Flow
> > Rate {m3/s}
> > > autocalculate, !- Evaporator Air Volumetric Flow
> Rate
> > {m3/s}
> > > Zone and Outdoor Air, !- Inlet Air Configuration
> > > HPWHAirOutletNode, !- Heat Pump Air Inlet Node Name
> > > HPWHAirInletNode, !- Heat Pump Air Outlet Node Name
> > > HPWHOutdoorAirInletNode, !- Outside Air Node Name
> > > HPWHExhaustAirOutletNode,!- Exhaust Air Node Name
> > > , !- Inlet Air Temperature Schedule
> Name
> > > , !- Inlet Air Humidity Schedule Name
> > > SPACE5-1, !- Inlet Air Zone Name
> > > Water Heater:Mixed, !- Water Heater Tank Type
> > > HPWHTank, !- Water Heater Tank Name
> > > , !- Water Heater Tank Use Side Inlet
> > Node Name
> > > , !- Water Heater Tank Use Side Outlet
> > Node Name
> > > Coil:DX:HeatPumpWaterHeater, !- DX Coil Type
> > > HPWHDXCoil, !- DX Coil Name
> > > 5.0, !- Minimum Inlet Air Temperature for
> > Heat
> > > Pump Compressor Operation {C}
> > > Zone, !- Compressor Location
> > > , !- Compressor Ambient Temperature
> > Schedule Name
> > > Fan:Simple:OnOff, !- Fan Type
> > > HPWHFan, !- Fan Name
> > > Draw Through, !- Fan Placement
> > > 15.0, !- On-Cycle Parasitic Electric Load
> {W}
> > > 5.0, !- Off-Cycle Parasitic Electric Load
> > {W}
> > > Zone, !- Parasitic Heat Rejection Location
> > > HPWHInletAirMixerNode, !- Inlet Air Mixer Node Name
> > > HPWHOutletAirSplitterNode, !- Outlet Air Splitter Node Name
> > > HPWHMixerInletAirSch; !- Inlet Air Mixer Schedule Name
> > >
> > >
> > > WATER HEATER:MIXED,
> > > HPWHTank, !- Name
> > > 0.3785, !- Tank Volume {m3}
> > > Hot Water Setpoint Temp Schedule, !- Setpoint Temperature
> > Schedule
> > > 2.0, !- Deadband Temperature Difference
> > {deltaC}
> > > 82.2222, !- Maximum Temperature Limit {C}
> > > CYCLE, !- Heater Control Type
> > > 5000, !- Heater Maximum Capacity {W}
> > > 0, !- Heater Minimum Capacity {W}
> > > , !- Heater Ignition Minimum Flow Rate
> > {m3/s}
> > > , !- Heater Ignition Delay {s}
> > > ELECTRICITY, !- Heater Fuel Type
> > > 0.95, !- Heater Thermal Efficiency
> > > , !- Part Load Factor Curve
> > > 10, !- Off-Cycle Parasitic Fuel
> > Consumption
> > > Rate {W}
> > > ELECTRICITY, !- Off-Cycle Parasitic Fuel Type
> > > 0, !- Off-Cycle Parasitic Heat Fraction
> > To Tank
> > > 30, !- On-Cycle Parasitic Fuel
> Consumption
> > Rate {W}
> > > ELECTRICITY, !- On-Cycle Parasitic Fuel Type
> > > 0, !- On-Cycle Parasitic Heat Fraction
> To
> > Tank
> > > ZONE, !- Ambient Temperature Indicator
> > > , !- Ambient Temperature Schedule
> > > SPACE5-1, !- Ambient Temperature Zone
> > > , !- Ambient Temperature Outside Air
> Node
> > > 2.0, !- Off-Cycle Loss Coefficient To
> > Ambient
> > > Temperature {W/K}
> > > 1.0, !- Off-Cycle Loss Fraction To Zone
> > > 2.0, !- On-Cycle Loss Coefficient To
> > Ambient
> > > Temperature {W/K}
> > > 1.0, !- On-Cycle Loss Fraction To Zone
> > > 0.00379, !- Peak Volumetric Use Flow Rate
> {m3/s}
> > > Hot Water Demand Schedule, !- Use Flow Rate Fraction Schedule
> > > , !- Cold Water Supply Temperature
> > Schedule
> > > , !- Use Side Inlet Node
> > > , !- Use Side Outlet Node
> > > , !- Use Side Effectiveness
> > > HPWHWaterOutletNode, !- Source Side Inlet Node
> > > HPWHWaterInletNode, !- Source Side Outlet Node
> > > 0.95; !- Source Side Effectiveness
> > >
> > >
> > > COIL:DX:HEATPUMPWATERHEATER,
> > > HPWHDXCoil, !- Coil Name
> > > 4000.0, !- Heating Capacity {W}
> > > 3.2, !- Rated COP {W/W}
> > > 0.6956, !- Rated SHR (gross)
> > > 29.44, !- Rated Evaporator Inlet Air Dry-
> Bulb
> > > Temperature {C}
> > > 22.22, !- Rated Evaporator Inlet Air Wet-
> Bulb
> > > Temperature {C}
> > > 55.72, !- Rated Condenser Inlet Water
> > Temperature {C}
> > > autocalculate, !- Rated Evaporator Air Volumetric
> > Flow
> > > Rate {m3/s}
> > > autocalculate, !- Rated Condenser Water Volumetric
> > Flow
> > > Rate {m3/s}
> > > No, !- Evaporator Fan Power Included in
> > Rated COP
> > > No, !- Condenser Pump Power Included in
> > Rated COP
> > > No, !- Condenser Pump Heat Included in
> > Rated
> > > Heating Capacity and Rated COP
> > > 150.0, !- Condenser Water Pump Power {W}
> > > 0.1, !- Fraction of Condenser Pump Heat
> to
> > Water
> > > HPWHInletAirMixerNode, !- Evaporator Air Inlet Node Name
> > > HPWHDXCoilAirOutletNode, !- Evaporator Air Outlet Node Name
> > > HPWHWaterInletNode, !- Condenser Water Inlet Node Name
> > > HPWHWaterOutletNode, !- Condenser Water Outlet Node Name
> > > 100.0, !- Crankcase Heater Capacity {W}
> > > 5.0, !- Maximum Ambient Temperature for
> > > Crankcase Heater Operation {C}
> > > wet-bulb temperature, !- Evaporator Air Temperature Type
> for
> > > Curve Objects
> > > HPWHHeatingCapFTemp, !- Heating Capacity Modifier Curve
> > Name
> > > (function of temperature)
> > > , !- Heating Capacity Modifier Curve
> > Name
> > > (function of air flow fraction)
> > > , !- Heating Capacity Modifier Curve
> > Name
> > > (function of water flow fraction)
> > > HPWHHeatingCOPFTemp, !- Heating COP Modifier Curve Name
> > > (function of temperature)
> > > , !- Heating COP Modifier Curve Name
> > > (function of air flow fraction)
> > > , !- Heating COP Modifier Curve Name
> > > (function of water flow fraction)
> > > HPWHPLFFPLR; !- Part Load Fraction Correlation
> Name
> > > (function of part load ratio)
> > >
> > > anarui.oliveira wrote:
> > > >
> > > > Maybe this additional information helps:
> > > >
> > > > ...I started out with a model of a boiler created with Compact
> > HVAC,
> > > > and then expanded it and substituted the boiler by the Heat
> Pump
> > Water
> > > > Heater.
> > > > The expanded model with the boiler works fine... so I guess I
> > missed
> > > > something when adapting it to a model with a heat pump?...
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "anarui.oliveira"
> > > > <anarui.oliveira@> wrote:
> > > >
> > > > Hi everyone.
> > > >
> > > > I modelled a system with a central Heat pump (air-to-water),
> > producing
> > > > heat for a hot water loop serving 3 Air Treatment Units and some
> > > > terminal unit ventilators, but the thermal heating rate/energy
> > produced
> > > > by the central heat pump is much (2-3 times) higher than the
> sum
> > of the
> > > > heating rates/energy of all the coils in the ATUs and terminal
> > units...
> > > > It seems as if the control os this central unit is not
> performing
> > > > properly, but I can't figure out why...
> > > >
> > > > Could anyone help?
> > > >
> > > > Thanks in advance,
> > > > Ana Rui.
> > > >
> > > > --- End forwarded message ---
> > > >
> > > >
> > >
> > > --
> > > Richard A. Raustad
> > > Senior Research Engineer
> > > Florida Solar Energy Center
> > > University of Central Florida
> > > 1679 Clearlake Road
> > > Cocoa, FL 32922-5703
> > > Phone: (321) 638-1454
> > > Fax: (321) 638-1439 or 1010
> > > Visit our web site at: http://www.fsec.ucf.edu 
> <http://www.fsec.ucf.edu>
> > >
> > > UCF - From Promise to Prominence: Celebrating 40 Years
> > >
> >
>
>  

-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL  32922-5703
Phone:   (321) 638-1454
Fax:     (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu

UCF - From Promise to Prominence: Celebrating 40 Years


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References:
- [EnergyPlus_Support] Re: Fwd: Central Heat Production vs terminal units
  - From: anarui.oliveira

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