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Advancements in Centrifugal Chillers Magnetic Bearing Oil-Free Technology

Bruce Barrett Product Sales Manager McQuay International

Minneapolis, Minnesota bruce.barrett@mcquay.com

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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

15

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