POTENTIAL OF CARBON DIOXIDE COMPRESSOR TECHNOLOGY FOR REFRIGERATION APPLIANCES

CENTRO STUDI GALILEO

INDUSTRIA & FORMAZIONE

CENTRO RICERCA AMBIENTE ED IMPRESAUNIVERSITA’ DEGLI STUDI DI MILANO

European seminar: carbon dioxide as a refrigerantMilan, 27th November 2004

POTENTIAL OF CARBON DIOXIDE COMPRESSOR TECHNOLOGY FOR REFRIGERATION APPLIANCES





Outline

• New Applications for an Old Refrigerant

• Making CO2 Refrigeration Technology Feasible

• Performance Assessment and Perspectives

• Preliminary Results from Appliances Tests

• Closure





New Applications for an Old Refrigerant

CO2 Refrigeration advertisement in a business magazine in 1921:

“1 to 150 tons in single units”

“The ideal equipment for Refrigeration purposes”

“Carbonic Safety System”

Source: South Central Library System’s website

Usage in the Past






CO2 Replacement - CFCs Era Begins

CFC granted patent by Thomas Midgley in 1931:

“...a process of heat transfer in which these desirable properties,

such as non-flammability and non-toxicity, are obtained in

combination with the desired boiling point.”

Source: United States Patent Trade Office






Reasons:

• International regulations on HFCs• Lack of long term solutions for refrigerant fluids• Environmental consciousness• “Ecological appeal”• Market demand

Applications Envisioned:

• Automobile Air-Conditioning• Heat Pump Water Supply Systems• Light Commercial Refrigeration (Beverage Cooling, Ice Cream Freezing, ... )

CO2 Revival





Making CO2 Refrigeration Technology Feasible

Refrigeration Means with Practical Use

• Vapor Compression• Vapor Absorption• Air-Cycle• Solid State (Thermo-Electric, ...)

• High Efficiency• Low Cost• Better Cost-to-Benefit Ratio • Simple Mechanical Embodiments

”...the refrigerating effect is produced by making a volatile fluid boil at a suitably low temperature...”






Vapor Compression Systems






Refrigeration Cycle Inefficiency

Typical conditions for MBP Application






TEWI Methodology

En1mGWPnLGWPTEWI )(

• Direct EffectGWP - Refrigerant Global Warming Potential [kgCO2/kg]

L - Annual Leakage Rate [kg/year]

n - Life time [years]

m - Refrigerant charge [kg]

- Recycling factor [%]

• Indirect EffectE - Annual energy consumption [kWh/year]

- CO2 emissions on energy generation

[kgCO2/kWh]

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

Emis

sion

s [k

g CO

2]

TEWI Analysis for a Light Commercial Refrigeration Appliance

R134a/32oC Ambient Temperature/15 Years Lifetime/75% Refrigerant Recovery Factor

TEWI Analysis 0.7 99.3

Direct Global Warming Potential [% of Total CO2 Emission]

Indirect Global Warming Potential [% of Total CO2 Emission]






Overcoming Inefficiency of the CO2 Refrigeration Cycle

32oC Ambient Temperature65% Relative Humidity





Performance Assessment and Perspectives

Phase I: CO2-Oriented Compressor Design

Results Efficiencies560.381.42

394.00 -70.92 82.0%21.28 93.4%301.80 62.1%4.50 -6.60 -

290.70 -70.82 -32.42 -187.46 35.02%121.81 -

65.65 -

Isentropic Power [W]Cycle Power [W]

Carnot Power [W]

Discharge [W]Effective Power [W]

Other Thermod. [W]Superheating [W]

Motor [W]Mechanical [W]

Indicated Power [W]Suction [W]

CO2 PrototypeName

Total Power [W]

Cooling Capacity [W]COP [W/ W]






Phase II: CO2-Optimized Compressor Design

Results Efficiencies683.291.71

398.70 -- 82.00%- 92.92%- 75.24%- -- -- -- -- -

228.58 35.02%148.53 -

80.05 -Carnot Power [W]

Superheating [W]Other Thermod. [W]

Isentropic Power [W]Cycle Power [W]

Indicated Power [W]Suction [W]Discharge [W]

Effective Power [W]

Name

Total Power [W]Motor [W]Mechanical [W]

Cooling Capacity [W]COP [W/ W]

CO2 Prototype






Compressor Data - Baseline and BenchmarkCompressor Model T 6213Z CO2 Phase I CO2 Phase II

Refrigerant fluid R134a R744 R744

Application Light commercialM-HBP

Light commercialMBP

Light commercialMBP

Version 220-240 V / 50 Hz 220-240 V / 50 Hz 220-240 V / 50 Hz

Evaporating temperature [ oC ] -10.0 -10.0 -10.0

Condensing temperature [ oC ] 42.0 85 bar (* ) 85 bar (* )

Return temperature [ oC ] 32.0 32.0 32.0

Liquid temperature [ oC ] 32.0 32.0 32.0

Cooling capacity [ W ] 767.0 676.8 756.3

COP [ W/ W ] 1.866 1.560 1.740

Compared to T 6213Z (Baseline) 0.0% -16.4% -6.8%(* ) Reference Pressure - only for Thermodynamic cycle comparison





Preliminary Results from Appliance Tests

Beverage Cooling - 405 Cans Vending Machine

32oC Ambient Temperature65% Relative Humidity337.7

334.3

306.8

275.0

290.0

305.0

320.0

335.0

350.0

T6213Z (R134a) CO2 Phase I CO2 Phase II

Ener

gy C

onsu

mpt

ion

[kW

h/m

onth

]





Closure

Concluding Remarks• All the comments stated below take into account HFC technology currently in

the field, without considering any improvement on it;

• Replacing current HFC refrigerant fluids by CO2 is meaningful only if the overall energy consumption is at least at the same level of the respective baseline;

• Theoretical CO2 refrigeration cycles point to efficiencies lower than their respective HFC cycles; the higher the ambient temperature the higher the penalty in efficiency is;

• In real applications, optimized CO2 compressors can deliver better compression and volumetric efficiencies than current HFC compressors;

• Superior compression and volumetric efficiencies can make the CO2 application feasible, overcoming the intrinsically low cycle efficiency;

• Preliminary results from an appliance testing employing optimized CO2 compressors have pointed to competitive performance in terms of energy consumption;





QUESTIONS ?

Contact Information:Ricardo Maciel

EMBRACO - Empresa Brasileira de Compressores SARui Barbosa 1020 - Costa e Silva

Joinville - SC - BrazilPhone: +55 47 441.2762

Fax: +55 47 441.2650email: [email protected]

POTENTIAL OF CARBON DIOXIDE COMPRESSOR TECHNOLOGY FOR REFRIGERATION APPLIANCES

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