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University of Wisconsin-Madison

Emerging Refrigeration Technologies

Brandon F Lachner, Jr

Research & Technology ForumMadison, WIJanuary 20-21, 2005

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Today…Current Industrial Refrigeration

Ammonia in a vapor compression cycle dominates the industrial refrigeration market

Beyond TodayWhat about other refrigerants?Other equipment/technologies?

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Ammonia as a Refrigerant

The GoodReasonable working pressuresHigh heat of vaporizationInexpensiveGood heat transfer characteristicsEnvironmentally-friendly

The BadToxicSlightly flammable

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Refrigerant Alternatives

HalocarbonsHigh costEnvironmental impactsFuture availability questionableCompatibility w/existing infrastructureFractionation (mixtures)

Secondary refrigerantHigh cost – capital & operating

Watertemperature-limitedHigh capital costLarge footprint

HydrocarbonsBoom!

Carbon dioxideHigh working pressures

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“If it isn’t broke…”

“That’s what we’ve always used…”Why fix it?

Potential for first cost and energy savingsMovement away from global warming and ozone depleting refrigerants

Montreal Protocol (1992)Kyoto Protocol (1999)

Improved reliabilityIncreased production

Inertia

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Vapor Compression Developments

Compressor technologyCool Compression® (Vilter Mfg)Triple Screw (Carrier Co)Semi-hermetic (Mayekawa Mfg)

OtherMembrane technology “purger” (Enerfex)

Vilter Cool Compression

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Cool Compression

Oil cooling for screw is accomplished using direct contact heat exchange

Oil-liquid ammonia interfaceLiquid ammonia helps de-foam oil

Oil separator acts as cooler and coalescerApplicable use is high-stage only

Source: Vilter

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Triple Screw

Two active compression channels rather than one with single- or twin-screw systemsTriple Screw may soon break into the air conditioning market up to 500 TR

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Refrigeration Cycle Alternatives

Including (but not limited to):MagneticThermoacousticAbsorptionCO2

TranscriticalCascade

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Magnetic Refrigeration

Shows promise in performanceAt 5 T magnetic field, Active Magnetic Regenerator Refrigerator (AMRR) performs @ 60% of Carnot (high temp only)

No direct environmental impactsNon-toxicScalability?

Current research is on small scale

Secure your valuables!!!

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AMRR operation

Utilizes materials that have a large magneto-caloric effect (MCE)

magnetic field induces temperature swings

Using spatially varying alloys of Gd/Si/Ge, a maximum MCE point (Curie Temperature) can be optimized for the regenerator bed

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Magneto-caloric Effect

200 225 250 275 300 325 3500

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4

6

8

10

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Temperature (K)

Adi

abat

ic T

empe

ratu

re C

hang

e (K

)

0-5 Tesla

0-2 Tesla

(Engelbrecht, 2004)

“A Numerical Model of an Active Magnetic Regenerator Refrigeration System”, Engelbrecht, Kurt Masters Thesis, University of Wisconsin-Madison, 2004.

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MagnetizationHot-to-Cold FlowCold-to-Hot FlowDemagnetization

Cold

ReservoirHot

Reservoir

Heat Rejection

Refrigeration

Active Magnetic Regenerative Refrigerator Cycle (AMRR)

(Engelbrecht, 2004)

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AMRR layout

Development of rotary magnetic regenerator bed is analogous to the advent of centrifugal compressors from recips

(Engelbrecht, 2004)

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Thermoacoustic

Tuned high volume sound (pressure) waves cool working medium

Requires a buffer volume, regeneratorUses benign medium such as helium as refrigerant

No direct environmental impactsNon-toxicBen and Jerry’s have installed this system as a small ice-cream freezer

Penn State Team

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Thermoacoustic LayoutResembles pulse tubes

Buffer volumeRegeneratorPiston (compressor)

Requires large regenerator for high capacity

(courtesy of Thermoacoustic Refrigeration Team at Penn State)

US Patent #6,725,670

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Thermoacoustic

Essentially a reverse-Stirling cycle

Regenerator TemperatureHot Cold

Load

Heat rejection

regeneration

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Transcritical CO2

“No” direct environmental impactsGWP, ODP

Extremely high working pressuresLow side ~215 [psia]High side ~>1050 [psia]

Finding application in near future in auto industry (small scale)

No pressure!

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Transcritical CO2

Cycle SchematicSmaller componentsGas cooler instead of condenser

Evaporator

Gas Cooler(Condenser)

Compressor

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Transcritical v. Subcritical Vapor Compression Cycles

Transcriticalcycle

Subcriticalcycle

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Cascade System (NH3-CO2)

“No” direct environmental impacts

GWP, ODP

Manageable working pressures

Low side 70 [psig]High side 300 [psig]

Industrial scale systems currently in operation in both Europe and US Photos: Nestlé

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Cascade System (NH3-CO2)

CO2

NH3

to coolingtower

from coolingtower

Refrigeration load

Condenser/Evaporator

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Absorption

Utilizes low quality energyAble to provide refrigeration capacity where electricity is not availableCan be useful for recovering waste energy (heat ~140°C)Poor performanceAmmonia among typical refrigerants

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Ammonia-Water Absorption Operation

Compression process is replaced with generator/ regenerator/ absorber combinationHeat is driving energy rather than shaft work

Source: Energy Solutions Center

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Absorption Layout

Water (absorber) allows ammonia to be pumped rather than compressed –less energy consumption

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Any promise?

GoodGoodGoodLowTrans-crit

PoorGoodPoorHighAbsorption

PoorPoorPoorHighAcoustic

FairGoodFairHighCascade

GoodGoodGoodLowMagnetic

OverallFlexibilityPerformCost

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Future of Industrial Refrigeration

The end of ammonia in industrial systems is not in sightIRC is developing an industrial refrigeration “Technology Map”

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Industrial Refrigeration Technology Map

New equipmentEmerging cycle technologiesEvaluation of potential for technology success

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University of Wisconsin-Madison

Thank You

Questions?