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Copyright 2001, Praxair Technology, Inc. All rights reserved. Copyright 2003 Praxair Technology, Inc.
ThermoacousticThermoacoustic
RefrigerationRefrigeration
Bayram Arman, Ph.D.Praxair, Inc.
Tonawanda, NY
Presented at ASHRAE Annual Meeting
Kansas City, MO, June 29, 2003
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Disclaimer
THIS INFORMATION WAS PRESENTED AT AN ASHRAE SEMINAR HELD
AT THE 2003 SUMMER MEETING IN KANSAS CITY, MO. THE SEMINAR
FORMAT IS TO PRESENT INFORMATION OF CURRENT INTEREST AND
TO PROVIDE A VENUE FOR INTERACTION BETWEEN ASHRAEMEMBERS. THESE SEMINARS SHOULD NOT BE CONSIDERED PEER-
REVIEWED (OR THE FINAL WORD ON ANY SUBJECT). ASHRAE HAS
NOT INVESTIGATED, AND ASHRAE EXPRESSLY DISCLAIMS ANY DUTY
TO INVESTIGATE ANY PRODUCT, SERVICE, PROCESS, PROCEDURE,
DESIGN, OR THE LIKE WHICH MAY BE DESCRIBED HEREIN. THEAPPEARANCE OF ANY TECHNICAL DATA OR EDITORIAL MATERIAL
IN THIS PRESENTATION DOES NOT CONSTITUTE ENDORSEMENT,
WARRANTY, OR GUARANTY BY ASHRAE OF ANY PRODUCT, SERVICE,
PROCESS, PROCEDURE, DESIGN, OR THE LIKE. NEITHER ASHRAE,
THE AUTHORS OR THEIR EMPLOYERS WARRANT THAT THE
INFORMATION IN THIS PRESENTATION IS FREE OF ERRORS. THEENTIRE RISK OF THE USE OF ANY INFORMATION IN THIS
PRESENTATION IS ASSUMED BY THE USER. BEFORE MAKING ANY
DECISION OR TAKING ANY ACTION ON THIS SUBJECT, YOU SHOULD
CONSULT A QUALIFIED PROFESSIONAL ADVISOR.
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Definitions
Thermoacoustic refrigerator is a device that converts acousticpower into refrigeration
Linear motor is a device that produces linear oscillatorymotion in a gas or acoustic power
Thermoacoustic engine is a device that produces linearoscillatory motion or acoustic power utilizing heat
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Outline
Introduction
Drive Options
Linear Motor Compressors
Standing Wave Thermoacoustic Coolers
No Feedback Thermoacoustic Cryocoolers (Orifice Pulse
Tubes)
Full Feedback Thermoacoustic Coolers
Free-Piston Stirling Coolers & Cryocoolers
Closure
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Introduction
New Opportunities
0
1
50
100
150
200
250
300
10 100 1000 10000 100000 1000000 10000000
Cold
Temperature(K)
Cooling Power (watt)
PHYSICS,
MEDICAL
RESEARCH
AIR SEPARATION & LNG
AIR CONDITIONING
RESIDENTIAL COMMERCIAL INDUSTRIAL
REFRIGERATION & FREEZING
VENDINGRESIDENTIAL
COMMERCIAL
New Markets
Vacuum TrapsMedical OxygenHigh Temperature SuperconductorsSensorsSmall LNGVOC RecoveryBiofreezing
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Introduction
Thermoacoustic Coolers
Robust, Static Cold Parts
Make it Reliable
Integral, Efficient Drivers
Make it Practical
Efficient, Scalable, Stirling Gas Cycle
Makes it Possible
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P
V
Qhot
Qcold
Introduction
Stirling Efficiency, Ideal & Real
Unlike the ideal cycle, the real machines
operate in a sinusoidal manner -- rounded P-V
for smooth operation
Qreg
Similar to any other real cycle, it has losses
associated
Adiabatic spaces
HX Temperature Differences
Mechanical Losses
Stirling cycle is made up of four reversible
process -- time-varying P-V in enclosed gas
The ideal cycle performance is Carnot
equivalent -- Tc/(Th-Tc) 9.0 @ 0C/30C, 0.3 @ 73K/30C
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Introduction
Thermoacoustic Refrigerators Are Acoustically-
Phased Stirling Systems
No Feedback (Orifice Pulse Tube):
Ideal Efficiency Tc/Th:0.9 @ 0C/30C, 0.24 @ 73K/30C
Same Cooling Physics, Frequency
Dependent Trade ideal efficiency for
mechanical simplicity
Real efficiencies similar under
100K!
Full Feedback = Full Stirling
Critical for high temperatures
Carnot equivalent ideal efficiencyTc/(Th-Tc)
Net mass flow in the feedback loopis detrimental
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Compressor
Heat ofCompression
Regenerator
QQ
Cold HeatExchanger
Pulse Tube
Q
Reservoir
Hot HeatExchanger
Orifice
Aftercooler
Piston moves down and adiabatically compress PT gas
PT gas flows through the orifice into reservoir and exchanges heat. Flow stops when PPT= Pave
Piston moves up and adiabatically expands gas in the PT
Cold low P gas in the PT is forced toward the cold end by gas flow from the reservoir
Refrigeration load is picked up by the cold gas and flow stops when PPT> Pave
Regenerator precools the incoming high P gas before reaches the cold end
Proper gas motion in phase with pressure is achieved by the use of orifice and reservoir volume tostore the gas at half cycle
Gas is in the pulse tube could be divided into three segments with middle segment is acting like adisplacer to insulate both ends
Gas in the pulse tube functions to transmit hydrodynamic power in oscillating gas system from one endto the other across a temperature gradient with a minimum power dissipation and entropy generation
Introduction
No Feedback Refrigerator (OPTR)
Tambient
Tcold
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Introduction
History of Development
Giffo
rd
Mc
Mahon
(1960s)
GM Refrigerator
Giffo
rd
&
Lon
gsw
otrth
(1960s
)
LANL
(198
0s)
Taco
nisOscilla
tions
&Rott
Standing Wave
Radebaugh & NISTTeam (1984-1995)
M
ikulin
M
BTI(1983)
No Feedback (Orifice Pulse Tube)
Low & High Frequency105K 60K
LANL(1997)
Garret (02)
Full Feedback
Free Piston StirlingPh
ilipsC
o.
(1946)
Herschel (1834)
Kirk (1861)
Stirling (1816)
Stirling Refrigerator
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Introduction
Practical Limits of Thermoacoustic Coolers
Capacity scales withcross section
Regenerator flow uniformity
0
50
100
150
200
250
300
1 10 100 1000 10000 100000 1000000 1000000
Cold
Temperature(K)
Cooling Power (watt)
AIR CONDITIONING
RESIDENTIALCOMMERCIALINDUSTRIAL
PHYSICS,MEDICALRESEARCH
AIR SEPARATION & LNG
REFRIGERATION & FREEZING
VENDINGRESIDENTIAL
COMMERCIAL
New MarketsVacuum TrapsMedical OxygenHigh Temperature SuperconductorsSensorsSmall LNG
VOC RecoveryBiofreezing
Frequency
Temperature: Fixed heat transfer length
High T
Acoustic Dissipation Penalty Regenerator low-T heat capacity
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Drive Options
Linear Motor (Electrodynamic)
Most Common Input Many Types
Burner
Engine
Refrigerators
Thermoacoustic Engine
Large Systems
Solid State (piezoelectric)
Low Efficiency, Stroke
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Drive Options
Electrodynamic Drives
Static Coil (Motor)
More Copper Fits! Efficiency w/o Large Moving Mass
Moving Magnet or Iron
Many Morphologies
One Type Spans The Opportunity Range There are many manufacturers
Moving Coil (Loudspeaker)
Cheap, less efficient
Better for low power
Standard for Military Cryocoolers (
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N S
S N
#1
#2
N S
S N
#1
#2
MID-STROKE, Showing Internal Cancellationand External Balanced Influences
FULL STROKE, ShowingResidual Cancellation
from Out Magnet
A
A
B
B
Drive Options
Linear Motor Drive Family
Moving Magnets on Small Core
Requires Rotational Control
True 1-D Zero-Wear Flexure
Enables Compact Plan, Scale-up
Standard Electric Motor Mfg Methods
100 to 10,000 Watt Developed
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Radially-Rigid Suspension
Easy Clearance Seals
Shock Proofing
Completely Sealed in Vessels ZERO Contamination
Modulating Operation
Low-Load Maintenance
Quick Cool-Down
Twin-STAR Arrangement
Near-zero Vibration
Drive Options
Linear Motors
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Family of PWGs 2x100 (2s114W)
2x300 (2s160W)
2x2000 (2s241W*) 2x5000 (2s297W)
2x10000 (2s362W)
*two housing styles
Drive Options
Picture of Pressure Wave Generators
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Drive Options
Linear Motor Based Compressors
When fitted with Reed valves the linear motor drivesbecome oil-free compressors
One manufacturer is developing first prototypes forcompressors up to 20kW input power
Another manufacturer commercialized small compressors(200W) for mechanical refrigeration
For the 200W compressors, a substantial efficiencyimprovement over the conventional compressortechnologies is reported!
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19921990 1994 1996 1998 2000 2002
Linear Motor Driven OPTR (LOPTR) 0.1 kW @ 80KFirst Tested
No Feedback Thermoacoustic Cryocoolers
Linear Motor
Pressure WaveGenerator
OPTR
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No Feedback Thermoacoustic Cryocoolers
80K OPTR -- Commercially Available
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No Feedback Thermoacoustic Cryocoolers
30K OPTR -- being Developed
Warm HX
Transition
Cold HX
LN2 HX
Inertance
Pulse Tube
2nd Stage
19921990 1994 1996 1998 2000 2002
LOPTR20kW CFIC Driver
0.5kW @ 30KFirst Tests
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No Feedback Thermoacoustic Cryocooler
The Largest Thermoacoustic Engine Driven OPTR
TADOPTR
2.1 kW @ 125KAchieves World Record
Performance
19921990 1994 1996 1998 2000 2002
TADOPTR Achieves2kW at 130K (-225F)and over 20% of Carnotin both TAD and OPTR
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No Feedback Thermoacoustic Cryocooler
The Largest Thermoacoustic Engine
19921990 1994 1996 1998 2000 2002
TASHE-OPTR II8 kW @ 125K
Startup
PX/LANL
TASHE-OPTR I0.5 kW @ 125K
First TestedPX/LANL
3 OPTRs - 8 kW cooling power
@ -150 oC
TASHE - 60 kW acoustic power@ 50 oC
Natural gas burner - 150 kW heat
@ 700 oC
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No Feedback Thermoacoustic Cryocoolers
Pulse tubes are commercially available.
0%
5%
10%
15%
20%
25%
10 100 1000 10000
Motor/Compressor Input Power (W)
TRW #126Raytheon #84
LMNIST
Sunpower
DRS #14
Sumitomo #83
Cryomech
PT -- Stirling Type
PT -- G-M Type
Stirling
G-M
MR J/T
Turbo-Brayton
Praxair
CarnotEfficiency%
80K
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Full Feedback Coolers
A university and an ice cream manufacturer are developingunits for ice cream display cases (Garret 2002)
Bellows Bounce (Compact) Vibro-Acoustic Design
No acoustic resonator, everything fits inside the bellows Motor mass resonates with bellows/gas stiffness Thermoacoustic-Stirling thermal core for higher efficiency
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Stirling Coolers & Cryocoolers
Helium working fluid
Light weight
Full turn down capability
High ambient operation
Good COPs
One manufacturer measured COP of 3 between 0 and30C
Development of units for cooling from ambient downto -80C is underway
A unit as cooler thermoelectric replacement iscommercialized by a Japanese manufacturer.
Stirling cryocoolers have been commercially available
Thermoaco stic Coolers and Cr ocoolers
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Thermoacoustic Coolers and CryocoolersAre Here! Reliable
Scalable
Efficient
Environmentally friendly
Full turndown
High ambient operation
Available Stirling coolers ambient down
to 70K
No feedback thermoacousticcryocoolers (pulse tubes) 150Kto 4K
0
50
100
150
200
250
300
1 10 100 1000 10000 100000 1000000 1000000
Cold
Temperature(K)
Cooling Power (watt)
AIR CONDITIONING
RESIDENTIALCOMMERCIALINDUSTRIAL
PHYSICS,MEDICALRESEARCH
INDUSTRIAL GAS SEPARATIONLNG
REFRIGERATION & FREEZING
VENDINGRESIDENTIAL
COMMERCIAL
New MarketsVacuum TrapsMedical OxygenHigh Temperature SuperconductorsSensorsSmall LNG
VOC RecoveryBiofreezing
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Linear Motor Compressors Are Here!
Reliable
Oil-free
Scalable Efficient
Full turndown
Commercially available
Linear Compressor
2x10kW Linear Motor
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Additional Slides
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Large Thermoacoustic Systems -- Introduction
Standing Wave Engine
Spontaneous acoustic oscillations occur onesa critical temperature gradient is established
A typical parcel of gas oscillates along the axis
During its travel it experiences changes intemperature caused by compression and
expansion of gas by the sound pressure andby heat exchange with solid wall
A thermodynamic cycle with the time phasingresults from the coupled pressure,
temperature, position and heat oscillations
Time phasing between gas motion andpressure is such that the gas moves hotward
while P is risingand coolward when pressureis falling
Deliberately imperfect heat transfer in order tointroduce a significant time delay between gas
motion and thermal expansion/contraction
TAMBIENT
THOT
QHeatSource
Stack
QSink
Resonator
StackTT
Blob Location
12
34
1
P
V
2
3 4
L Th i S I d i
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Large Thermoacoustic Systems -- Introduction
Traveling Wave Engine
TAMBIENT
THOT
Mass flux
suppressor
Thermal buffer tube
Feedback Inertance
Compliance
Regenerator
Resonator Conversion of heat to power
occurs in the regenerator
Good heat transfer between the
solid and gas is required Gas moves toward the hot HX
while the P is highand towardambient HX while P is low
Acoustic power must be injectedinto ambient end of theregenerator in order to amplify theacoustic power
Swift et al. at LANL introduced ajet pump or mass flux suppressorto get substantial powerproduction
RegenT
Blob Location
3
21
4
1
P
V
2
4
3
Heate
d
Coole
d