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Advancements in Centrifugal Chillers Magnetic Bearing Oil-Free Technology
Bruce Barrett Product Sales Manager McQuay International
Minneapolis, Minnesota [email protected]
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• Energy cost expected to rise
• HVAC equipment accounts for over 25% of the
primary energy consumed in commercial buildings in
the US1
• Energy efficiency and reliability are key concerns
Today’s Building Market Demands
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•Best Water Cooled Chiller Efficiency
Water-cooled, centrifugal chillers are the most versatile class of
chillers available, meeting customer needs in capacities > 100 Tons
•How do you improve what is already great? Centrifugal Chillers are the largest consumer of energy in the HVAC
system
•Engineering/design improvements limited to <2% were considered significant! No room to get better…maybe
Efficiency improvements difficult within same framework of the
technology
Past and Current Technologies
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New Technology/New Standards in Efficiency
High Pressure Refrigerant
Permanent Magnet
(PM) Motors
Magnetic Bearings
High Speed VFDs
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Enabling Technologies for Efficiencies
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What’s really important?
System Energy Efficiency and Operating Costs
Sustainability and Green
+ + = High
Efficiency
Reduced
Maintenance Sustainability
Lower Total
Cost of
Ownership How were the choices made?
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Crucial Design Choice
…the right refrigerant
Refrigerant
Specific
Volume,
ft3/lb
Normalized
Flow Rate,
CFM/ton
R-123 5.9327 18.33
R-134a 0.9528 2.86
Conditions:
40°F saturated vapor
5.78 psia for R-123
49.94 psia for R-134a
100°F saturated condensing
8°F subcooling and 0.5°F superheat
R-123
R-134a
Positive Pressure Keep contaminants out
Low specific volume
Lower normalized flow rate (cfm/ton)
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Crucial Design Choice
…Motor Type
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100 110
Eff
icie
ncy (
%)
Percentage Speed
Induction Motor
Permanent magnet synchronous motor
25-30%
Efficiency Gain
5-7%
Efficiency Gain
0
5
10
15
20
25
30
35
0 2000 4000 6000 8000 10000 12000 14000 16000 18000
fric
tio
nal p
ow
er
loss
es
(h
p)
speed (rpm)
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Crucial Design Choice…Bearing Type
Hydrodynamic has significant frictional power losses
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Crucial Design Choice…Bearing Type
Magnetic Bearings-very limited losses
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Advancements in Magnetic Bearings
High speed digital processing
Lower cost than 5-10 years ago
High reliability
Standardized design
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Comparisons
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DCBA
NPLVorIPLV
12.045.042.001.0
1
Controlling the compressor speed …what works best?
Where:
A = kW/ton at 100% & 85°F CEWT
B = kW/ton at 75% & 75°F CEWT
C = kW/ton at 50% & 65°F CEWT
D = kW/ton at 25% & 65°F CEWT
AHRI Standard 550/590-2003, Appendix D
Full Load 1%
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0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80 90 100 110
kW
/ t
on
Chiller percent load
Fixed speed
Traditional VFD
High speed VFD w/
Magnetic Bearings 10% energy
reduction
Fixed Speed? Traditional VFD?
High speed VFD w/Magnetic Bearing?
~ $243,287/year
~ $164,934/year
~ $131,709/year
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Sustainability?
From ASHRAE Research Project 751-RP,
“Experimental Determination of the Effect of Oil on
Heat Transfer with Refrigerants HCFC-123 and
HFC-134a”,
Conclusions and Recommendations:
“The effect of POE oil on the heat
transfer coefficient of R-134a flowing
across a bundle of Turbo-B2 (HP) tubes
is a reduction in heat transfer
coefficient. The heat transfer ratio
drops steadily with oil concentration
and reaches a value of 0.65 [from 1.0
normalized] at an oil concentration of
10%.”
Small grooves or dimples in the tubes create more surface area and better heat transfer. However, they
also hold onto oil
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Sustainability Benefits
Positive pressure, oil-free design eliminates the
performance degradation due to non-condensables and oil
contamination of the refrigerant
Source: The News, 04/15/04, by Jack Sine
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3.5% Oil in
Refrigerant =
8% Efficiency
Loss
1 2 3 4 5 6 7 8
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14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
.576 kw/ton
.38 IPLV .622 kw/ton
.410 IPLV 7-12 gallons
Oil degrading performance is counter to sustainability!
Are you getting what you paid for long term?
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More Sustainability Benefits
Traditional Centrifugal
Chiller
Oil-Free Chiller
Oil YES NO
+ Oil Heater YES NO
+ Oil Cooler YES NO
+ Oil Pump/Starter YES NO
+ Oil Reservoir YES NO
+ Oil Filter YES NO
+ Oil Piping/Valving YES NO
+ Oil
Sensors/Controls
YES NO
+ Annual Oil
Analysis
YES NO
= More things to break, more
maintenance, more $
No energy losses, no concerns,
no annual oil change and
disposal, maintenance savings
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Let’s make this simple:
Oil in the chiller evaporator creates a decrease
in efficiency over time as the tubes foul,
lessening heat transfer. The best efficiency you
can get out of an oil chiller is when it first starts
up.
No oil in the chiller equates to less maintenance,
less start up concerns, no other parasitic loads
related to oil.
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• Resistant to Power Line Disturbances
• Rides through voltage drops
• Meets semi conductor industry standard SEMI F47
__________________________________________________
Regenerative power system keeps bearings powered until shaft stops spinning
• Rides through short duration power loss
• Extremely low inrush at Start Up
Other Advantages
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• Low Maintenance-no oil related issues
• Reliability-no friction, less wear
• Maximum equipment uptime
• Quiet operation
• Ease of installation-compact
• Ease of service
• Utilities- rebates improved for better for IPLV
• Some even giving bonus credit for being oil-free!
What Else?
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Magnetic Bearing Chiller Timeline
2004/2005
First Centrifugal
Chiller for
commercial use
Used on Navy ships
and the aerospace
industry prior decade
2006
~100 installed
2007
~500 Installed
2008
~800 Installed
2 Other major
manufacturers join
market
2009
>40% of Centrifugals
<400 ton are
Magnetic Bearing
2010
Single compressor
developed for
markets up to 700
tons
This is not a new product, only
gaining more momentum as the
industry understands the
benefits and confidence in the
technology
2011
At least 4
manufacturers with
AHRI certification
now in market
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Installations
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• Higher first-cost
• Limited voltages and frequency (460V and 575V)
• New skills /concepts required for servicing
• Perception, taking the technology leap still real
Challenges
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Lower Total
Cost of
Ownership
Sustainability Reduced
Maintenance
(No oil, No purge)
High
Efficiency
+ = +
What does the technology mean to owners?
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Thank you!
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• Refrigerant data for R-123 and R-134a, ASHRAE Handbook Fundamentals, I-P Edition, 2005.
• Kauffman, R., ASHRAE Research Project 601-TRP, “Chemical Analysis and Recycling of Used Refrigerant From Field Systems”, April 1990.
• Payvar, P., ASHRAE Research Project 751-RP, “Experimental Determination of the Effect of Oil on Heat Transfer with Refrigerants HCFC-123 and HFC-134a”, June 1999.
• Edney, S., Waite, J., and DeCarnillo, S., “Profiled Leading Edge Groove Tilting Pad Journal Bearing for Light Load Operation”, Dresser-Rand, Wellsville, NY, 2003
Bibliography