COMPRESSOR TECNOLOGY
FOR THE LOW GWP
REFRIGERANTS
London - 26° April 2012
RAC question time
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Eng. Marco Caldara
Frascold R&D laboratory manager
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Introduction
Compressor
Technology
Refrigerants
and Application
Engineering
Manufacturing
and Process
Engineering
Frascold Research
Philosophy
Material
Sciences
Compressor
Design
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Forensic
Engineering
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Current activities
Refrigerants
• HFO
• R407F
• CO2
Compressor design
• Design evaluation for drop-in allowance
• Design evolution for performance increasing
• Application envelope extensions
Validating application
• Suggest refrigerant choice
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• Hybrid system
• Field test in different location for seasonal
TEWI calculation purposes
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R&D case study
R1234ze
TESTING
EXPERIENCE
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Summary
Testing routine instruction
Testing equipment and methods
Refrigerant properties databases
Results
Operations
Current state of test program
Design evolution
Selection software update
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Testing routine instruction
TEST PLAN
1. Measure compressor parts
2. Assembling compressor
3. Tightness test
4. Oil charge
5. Installing on test rig and evacuate for 12 h
6. Test and record time + working condition
7. Recover refrigerant and uninstall from test rig
8. Taking oil sample for analysis
9. Dismantle compressor
10.Measure compressor part (500 h).
Each test result contributes to the entire project final result
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Test equipment and methods
TEST RIG: 300kW
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Test equipment and methods
TEST RIG: 300kW
 Built by ILK Dresden in 2004.
 Test according to EN13771-1
 Two Coriolis mass flow meter
 LP side, method D1
 HP side, method D2
 Oil separator
 Power supply from stabilized grid
 Four independent PID controllers
 Pressure measurement uncertainty lower than 1%
 Temperature measurement uncertainty lower than 0,3 K
 Power measurement uncertainty lower than 1%
 Water cooled condenser and subcooler
 Performance uncertainty lower than 5%
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Test equipment and methods
PERFORMANCE DATA PROCESSING STEP
1.
2.
3.
4.
5.
6.
7.
8.
9.
Placing testing point
Expect limits
Break-in time (24 h)
Reproduce conditions
Go outside limits
Check results
Use interpolation software
Evaluate efficiency curve
Create performance model
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Refrigerant databases
REFRIGERANT PROPERTIES DATABASE:
 NIST refprop 9.0
 ILK REFLIB for MS Excel 2.1
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Results – key points
Compressor performance
 Performance test
 Numeric simulation
Refrigerant comparison
Oil behavior
Compressor parts wearing
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Results – performance test
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Results – Numeric simulation
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Results – Refrigerant Comparison
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Results – Oil behavior
EVALUATED OIL:
 POE 68 cst
 PAG 68 cst
 POE 170 cst (screw)
 POE 68 cst
Oil level was regulated at half of the sight glass on compressor
crankcase by an optical level switch.
 LUBRICATION AT COLD START UP
 SUDDEN PRESSURE DECREASE (FOAM)
 FORCED LUBRICATION – PUMP
DIFFERENTIAL PRESSURE
 GAS TRAPPING WHEN DISCARDED
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Results – compressor parts wearing
EVALUATED COMPONENTS:
 PISTON AND PISTON RINGS
 SHAFT
 RODS
 BUSHES
 VALVE PLATE REEDS
 LIGHT WEARING (NORMAL)
 NO OVERHEATING SIGN ON VALVE
REEDS AND ROTATING PARTS
 ABSENCE OF DIRT OR PARTICLES
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Operations
NEEDING ADDITIONAL CARE FOR:
 LOADING – UNLOADING OF THE REFRIGERANT
 FLAMMABILITY ISSUE: VENTILATION OF AREA
 STOCK AND HANDLING
 VACUUM OPERATION
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 No difference in loading operation, but
lower pressure at given temperature
 Same ambient condition
 Same stock area and procedure
 Additional vacuum time to sample oil
after test
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Test program
 1° step: drop in of refrigerant in standard model
 2° step: Evaluated R134a model
range
 3° step: HFO dedicated model to enhance
favorable behavior
 4° step: field test running and confirmation test
 99% compatible with standard model
(dedicated oil)
 different performances requires
technology adaption
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Design evolution
•New valve
plate
•Reduced
clearances
•Motor optimized
for HFO
•Optimized
bore-stroke
ratio
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Design evolution
 Different motor size tested to
catch higher efficiency
 different bore-stroke solutions
will be evaluated in future.
 New design of valve plate
under evaluation
 Thanks to lower power consumption
motor
efficiency
improvement
is
possible and necessary
 Shorter stroke compression helps with
low density refrigerant in suction stage
 Valve plate for higher specific volume
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Selection software update
 Refrigerant model available
 Compressor efficiencies available for tested models
 Other models could be calculated having tested
performaces with HFC and conversion tools
 Models need confirmation test on oher sizes
 Thanks to similarity with R134a
conversion is plausible and tested to
define accuracy
 Performance calculation in progress.
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Thanks !
COMPRESSOR TECNOLOGY
FOR THE LOW GWP
REFRIGERANTS
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