Variable Capacity Heat
Pump RTF Sub-Committee
February 27, 2013
VRF Fan Energy Use and Part-Load
Performance
Richard Raustad, Senior Research Engineer
Florida Solar Energy Center
rraustad@fsec.ucf.edu
Full-Load Cooling Performance
Controlled Region
Uncontrolled Region
Full-Load Heating Performance
Manufacturer Performance Correction
(surrogate for part-load performance)
170
136
102
68
34
0
21 kW
72 kBTU/hr
28.1 kW
96 kBTU/hr
EnergyPlus Cooling Model Inputs
AirConditioner:VariableRefrigerantFlow,
autosize,
3.802,
-5,
43,
!- Rated Total Cooling Capacity {W}
!- Rated Cooling COP {W/W}
!- Minimum Outdoor Temperature in Cooling Mode {C}
!- Maximum Outdoor Temperature in Cooling Mode {C}
VRFCoolCapFT,
!- Cooling Capacity Ratio Modifier Function of Low Temperature Curve Name
VRFCoolCapFTBoundary, !- Cooling Capacity Ratio Boundary Curve Name
VRFCoolCapFTHi,
!- Cooling Capacity Ratio Modifier Function of High Temperature Curve Name
VRFCoolEIRFT,
!- Cooling Energy Input Ratio Modifier Function of Low Temperature Curve Name
VRFCoolEIRFTBoundary, !- Cooling Energy Input Ratio Boundary Curve Name
VRFCoolEIRFTHi,
!- Cooling Energy Input Ratio Modifier Function of High Temperature Curve Name
CoolingEIRLowPLR,
CoolingEIRHiPLR,
CoolingCombRatio,
VRFCPLFFPLR,
!- Cooling Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name
!- Cooling Energy Input Ratio Modifier Function of High Part-Load Ratio Curve Name
!- Cooling Combination Ratio Correction Factor Curve Name
!- Cooling Part-Load Fraction Correlation Curve Name (cycling losses)
Creating Performance Curves
• Raustad, R.A., 2012. Creating Performance Curves for
Variable Refrigerant Flow Heat Pumps in EnergyPlus,
FSEC-CR-1910-12.
https://securedb.fsec.ucf.edu/pub/pub_search
https://securedb.fsec.ucf.edu/pub/pub_show_detail?v_pub_id=4588
[59 F]
[60.8 F]
[64.4 F]
[68 F]
[71.6 F]
[75.2 F]
[41 F]
[50 F]
[86 F]
[95 F]
[78.8 F]
[-4]
[F]
[131]
Laboratory Measured Data
Full-load Cooling Performance
AHRI 1230
Buried TSTAT
setting
[-17.7]
[10]
[37.8]
[C]
[65.6]
[29.4/21.1]
[29.4/19.4]
[29.4/17.2]
[26.7/21.1]
[26.7/19.4]
[26.7/17.2]
[26.7/15.6]
[23.8/21.1]
[23.9/19.4]
[23.8/17.2]
[23.9]
[20.6]
WB
[17.8]
[15.0]
Normalized Capacity
Measured part-load operation
[15.3 kW]
Outdoor Temperature (F) [C]
[23.9 C]
[29.4 C]
[35 C]
[40.5 C]
[26.7 C/ 19.4 C]
[15.3 kW]
170
136
102
68
34
0
Model Characteristics
170
136
102
68
34
[kW]
[58.6]
Major Difference between VRF HP’s
and Conventional HP’s
• Avoid duct losses when using ductless terminal
units (no heat gain or leakage)
Major Difference between VRF HP’s
and Conventional HP’s
• Avoid duct losses when using ductless terminal
units (no heat gain or leakage)
Major Difference between VRF HP’s
and Conventional HP’s
• Avoid duct losses when using ductless terminal
units (no heat gain or leakage)
• Fan energy savings for ductless terminal units
Major Difference between VRF HP’s
and Conventional HP’s
• Avoid duct losses when using ductless terminal
units (no heat gain or leakage)
• Fan energy savings for ductless terminal units
• Moderate part-load
savings
170
136
102
68
34
[kW]
[58.6]
Major Difference between VRF HP’s
and Conventional HP’s
• Avoid duct losses when using ductless terminal
units (no heat gain or leakage)
• Fan energy savings for ductless terminal units
• Moderate part-load savings
• Space savings for refrigerant lines vs air ducts
Major Difference between VRF HP’s
and Conventional HP’s
• Avoid duct losses when using ductless terminal
units (no heat gain or leakage)
• Fan energy savings for ductless terminal units
• Moderate part-load savings
• Space savings for refrigerant lines vs air ducts
• Individual zone control
Future work
• Need more laboratory research and published
experimental data
• Better understanding of control logic
• Field demonstrations need more information
• Work closely with manufacturer’s
Questions?
Richard Raustad
rraustad@fsec.ucf.edu