Previously, I modeled a water system with desuperheater in Model 1 which gave happy results (about half water heating energy saving). Now I need to integrate this technology into another model( Model2) with exactly the same approach. However, the Model 2 results showed about 10X water heating energy usage than its baseline, which is unreasonable.
The approach I used to model desuperheater is quite straightforward, I'd like to elaborate as following:
- I created a constant temperature schedule of 55C (setpoint is 52.6667C)
.
Schedule:Constant,
desuperheaterStp, !- Name
Temperature, !- Schedule Type Limits Name
55; !- Hourly Value
- I used
Coil:WaterHeating:Desuperheaterobject, the snippet was like
.
Coil:WaterHeating:Desuperheater,
Desuperheater, !- Name
, !- Availability Schedule Name
desuperheaterStp, !- Setpoint Temperature Schedule Name
2, !- Dead Band Temperature Difference {deltaC}
0.25, !- Rated Heat Reclaim Recovery Efficiency
50, !- Rated Inlet Water Temperature {C}
35, !- Rated Outdoor Air Temperature {C}
60, !- Maximum Inlet Water Temperature for Heat Reclaim {C}
, !- Heat Reclaim Efficiency Function of Temperature Curve Name
DesuperheaterIn, !- Water Inlet Node Name
DesuperheaterOut, !- Water Outlet Node Name
WaterHeater:Mixed, !- Tank Object Type
water heater, !- Tank Name
Coil:Cooling:DX:SingleSpeed, !- Heating Source Object Type
central ac clg coil, !- Heating Source Name
0.001, !- Water Flow Rate {m3/s}
, !- Water Pump Power {W}
0.2; !- Fraction of Pump Heat to Water
- And finally I got these two water nodes connected with
WaterHeater:Mixed
.
WaterHeater:Mixed,
res wh, !- Name
0.136274824222915, !- Tank Volume {m3}
WH Setpoint Temp, !- Setpoint Temperature Schedule Name
2, !- Deadband Temperature Difference {deltaC}
99, !- Maximum Temperature Limit {C}
Cycle, !- Heater Control Type
5500.06477392209, !- Heater Maximum Capacity {W}
0, !- Heater Minimum Capacity {W}
0, !- Heater Ignition Minimum Flow Rate {m3/s}
0, !- Heater Ignition Delay {s}
Electricity, !- Heater Fuel Type
0.8, !- Heater Thermal Efficiency
, !- Part Load Factor Curve Name
0, !- Off Cycle Parasitic Fuel Consumption Rate {W}
Electricity, !- Off Cycle Parasitic Fuel Type
0, !- Off Cycle Parasitic Heat Fraction to Tank
0, !- On Cycle Parasitic Fuel Consumption Rate {W}
Electricity, !- On Cycle Parasitic Fuel Type
0, !- On Cycle Parasitic Heat Fraction to Tank
Outdoors, !- Ambient Temperature Indicator
, !- Ambient Temperature Schedule Name
, !- Ambient Temperature Zone Name
Model Outdoor Air Node, !- Ambient Temperature Outdoor Air Node Name
0.704227539803499, !- Off Cycle Loss Coefficient to Ambient Temperature {W/K}
1, !- Off Cycle Loss Fraction to Zone
0.704227539803499, !- On Cycle Loss Coefficient to Ambient Temperature {W/K}
1, !- On Cycle Loss Fraction to Zone
, !- Peak Use Flow Rate {m3/s}
, !- Use Flow Rate Fraction Schedule Name
, !- Cold Water Supply Temperature Schedule Name
Node 13, !- Use Side Inlet Node Name
Node 14, !- Use Side Outlet Node Name
1, !- Use Side Effectiveness
DesuperheaterOut, !- Source Side Inlet Node Name
DesuperheaterIn, !- Source Side Outlet Node Name
1, !- Source Side Effectiveness
Autosize, !- Use Side Design Flow Rate {m3/s}
Autosize, !- Source Side Design Flow Rate {m3/s}
1.5, !- Indirect Water Heating Recovery Time {hr}
IndirectHeatPrimarySetpoint, !- Source Side Flow Control Mode
, !- Indirect Alternate Setpoint Temperature Schedule Name
General; !- End-Use Subcategory
Water system energy results:
Model1
- Baseline : 13.21
- Desuperheater : 6.07
Model2
- Baseline : 11.09
- Desuperheater : 119.2
