Thermoacoustic heat driven cooling
Kees de Blok
Aster Thermoacoustics, Smeestraat 11, 8194LG Veessen, The Netherlands
c.m.deblok@aster-thermoacoustics.com
Douglas Wilcox
Chart-Qdrive, 302 10th Street, Troy, NY 12180, USA
douglas.wilcox@chartindustries.com
Developments since the 1e workshop on thermoacoustics
Features of multi-stage TA engines
Multi-stage TA engine application examples
Thermoacoustic liquefaction of natural gas
Conclusions
7 april 2015
1
Developments since 1e workshop on thermoacoustics
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Pulse tube cryocoolers or cold heads
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Thermoacoustic engines with standing wave
resonator
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Since 1980
Driven by (E-A) pressure wave generator
Commercially available today
Image: www.qdrive.com
Since 1997
High efficiency
High onset and operating temperatures
Large internal (resonator) volume
Most studied / copied configuration
Multistage thermoacoustic engines with
traveling wave resonance and feedback
circuits
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Image: www.lanl.gov
Since 2008
Low onset and operating temperatures
Small internal (feedback) volume
Prototypes build up to 100kW T at 160C
Image: www.aster-thermoacoustics.com
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Features of multi-stage TA engines
Typical TA engine operating temperatures
Properties of multi-stage traveling wave
thermoacoustic engines
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Acoustic power gain proportional with
number of stages
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Less acoustic loop power relative to the
net acoustic output power (more compact
design)
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Onset temperature difference < 30 C
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"Economic" operating temperature
difference > 100 C
4-stage thermoacoustic traveling wave engine/cooler (THATEA project, 2010)
Enables low and medium temperature heat
sources as useful input heat
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Waste heat (industry)
Flue gas (e.g. CHP, …)
Solar heat (vacuum tube collectors)
……..
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Features of multi-stage TA engines
1) Default acoustic impedance matching
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In case of 4 stage TA engines, acoustic in- and output impedances are matched by default, because of the ¼ 
mutual distance between stages.
2) Traveling wave feedback multi-stage systems build so far hardly showed any streaming, Why?
Streaming is proportional with pressure amplitude and transported heat is proportional with temperature
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For the same acoustic power, pressure amplitude in traveling wave feedback systems is nearly half the amplitude
in standing wave systems
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Multi-stage systems typcally operate at low and medium temperatures
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Asymmetry in minor losses at the in- and output junctions to the feedback tubes due to difference in local gas
density (temperature) .
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Multi-stage TA engine application examples
ThermoAcoustic Power (TAP)
Conversion of industrial waste heat into electricity
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Dutch SBIR project, phase2
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Design and built of a TAP converting 100 kW
waste heat at 160ºC into 10 kW electricity
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Location: Smurfit Kappa Solid Board,
Nieuweschans(Gr), The Netherlands
3m
100 kW T Thermo Acoustic Power generator
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Multi-stage TA engine application examples
Solar powered cooling (SOTAC)
Add-on for vacuumtube collector systems
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Latitude <35: Cooling only
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Latitude >35: Combined heating and
cooling
SOTAC demonstration setup (2012)
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Thermoacoustic liquefaction of natural gas
Thermoacoustic liquefaction of natural gas (LNG)
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Basic idea since 1998 by LANL (Swift), Cryenco (later
Praxair)
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Thermoacoustic Stirling engine (TASE) drives multiple
pulse tubes sharing the same standing wave resonator
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Minimum engine input temperature:
TH_engine = TC_engine . TH_cooler /TC_cooler
In theory: TH_engine = 330*300/110 = 900K (627C)
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In practice: TH_engine > 900C
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High temperature (red) hot hex and pressure vessel
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Limited heat reduction burned gas (1300 C  900 C)
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Recuperation required, but limited by high exhaust
temperature
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High temperature contruction materials required
 Construction cost too high to become economic viable
Image: www.lanl.gov
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Thermoacoustic liquefaction of natural gas
Thermoacoustic liquefaction of natural gas (LNG) or bio
gas for transport and storage
The idea behind:
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Combine high performance pulse tube(s) with low input
temperature multi-stage traveling wave thermoacoustic
engine to lower input temperature
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Reduce minimum engine input temperature by # stages
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Typical engine input temperature less than 300C
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Improved heat reduction burned gas (1300 C  300 C)
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Recuperation not required (optional)
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Allows for use of ordinairy construction materials
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 Cost reduction brings back the concept on stage
 Simple construction
 Scalable
 No moving parts
 Little or no maintenance
 Stand-alone operation
7 april 2015
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Thermoacoustic liquefaction of natural gas
The experiment measurement layout
Gas mean pressure: 2.4 Mpa
Heat source: thermal oil heater
Heat sink: water cooling
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4-stage traveling wave engine
 Available at Asterthermoacoustics
 Gas: helium-argon
 Frequency: 50-77Hz
(set by ratio helium-argon)
 Pressure amplitude cold hex #4:
65 kPa ( dr: 2.7%)
 Theat source : 224C
 Theat sink : 25C
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Cold head
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Type 102 supplied by Qdrive
Gas: helium
Operating frequency: 60Hz
Pressure amplitude cold head:
226 kPa ( dr: 9.4%)
Electric heater: 5.2
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Thermoacoustic liquefaction of natural gas
First experiment january 2014
Results
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First experiment
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Reached a cold head temperature of -110C
Proved the concept
Recent experiment
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Reduction of engine losses
Heat load added to cold head
Modified gas filling system
Cold head cooling power at engine input temperature of 224C
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Cold head
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temperature: -160C
Heat sink cold head 25C
TA engine
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Heat input temperature: 224C 
Heat sink: 25C
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Conclusions
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Brief overview of features and projects making use of multi-stage traveling wave thermoacoustic engines
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Alternative concept for liquefaction of natural gas or bio-gas for transport and storage
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Combines a high performance pulse tube and a multi-stage traveling wave thermoacoustic engine
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Reduced engine input temperature down to 300C
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High temperature reduction (extracting more heat) of combustion gas prior to exhausting
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More than one order of cost reduction by using ordinary construction materials
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Brings back on stage, the concept of (combustion) heat driven liquefiers, not only for liquefaction of natural gas
(LNG) but also for storage and transport of bio-gas or other gasses
Thermoacoustics is on its way to full scale techno-economic viable applications
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