Petter Neksa - Sintef Energy Research - ULTIMI RISULTATI NELLA REFRIGERAZIONE CON R744

Technology for a better society 1


SINTEF - A contract research organization based in Trondheim, Oslo, Bergen, Stavanger and Tromsø• SINTEF is one of the largest independent research organisations in Europe.

Social perspective

SINTEF wishes to contribute to the creation of value

and to a society in healthy sustainable development.

Business concept

SINTEF sell research-based knowledge and related services to Norwegian and international clients.

Fundamental values

Honesty, Generosity, Courage and Unity

SINTEF has 2145 employees,

1600 situated in Trondheim and 430 in Oslo.

SINTEF receives only 3% basic grants

Norway

Technology for a better society

CO2 applications, status transcritical

• Already developed and commercialised– Heat pump water heaters –

domestic, commercial and industrial sized

– Commercial refrigeration systems, supermarkets

– Beverage coolers – Ice cream chest freezers– Water chillers for moderate

climates, air conditioning and industrial

– Transport refrigeration (bus, train)

• Already developed – not yet commercialised– Mobile air conditioning systems

• Under development– Mobile heat pumps – Transport refrigeration systems

(containers, truck, marine)

• Under development, contd– Residential heat pumps (space heating

and reversible)– Vending machines for combined hot

and cold beverages – Combined heating and cooling of non-

residential and residential buildings– Heat pumps for space heating and

combined space and water heating– Heat pump dryers of residential and

commercial size, e.g. laundry applications

– Rankine power cycles for utilisation of low temperature surplus heat

• Early development– Residential air-conditioning systems – Water chillers for hot climates, air

conditioning and industrial– Industrial refrigeration and heat pumps


Commercial refrigerationLargest refrigerant GHG emissions of the refrigeration sector, more than 40% of the CO2-eq emissions

• General scepticism to CO2– pressure– efficiency

• However– Reduced pumping

power LT– Retrofit R22

• Rolfsmann 1995?

High pressurecompressor

Condenser

Intermediatepressurevessel

Low pressurecompressor

NH evaporatorCO condenser

CO liquidseparator

Brine cooler.

3

2

2

CO AS SECONDARY REFRIGERANT2

Condenser

NH compressor

CO compressor

Brine cooler.

3

2

Evaporators

Low pressure

reciever

Cascade

cooler

CO IN LOW TEMPERATURE CASCADE STAGE2

High pressurecompressorGas

Intermediatepressurevessel

Low pressurecompressor

Brine cooler.

reciever

Low pressure

Evaporators

cooler

TWO STAGE CO SYSTEM.2

CO2 as heat transfer fluid CO2 transcritical /(subcritical)CO2 in low temp cascade stage

• Good arguments for CO2 LT stage– No pump– Reduced swept vol– Standard pressure

level• And

– Very efficientcompression

• Norild 1993

• Why not all-CO2?• Benefits

– One refrigerant– Small dimensions– Less costly?

• Status– Several supermarket

chains and manufacturers has decided for CO2


CO2 is ideally for heat recovery concepts in moderate and colder climates (Kroppanmarka)

Energy Well

Accumulation

Tanks Floor Heating

DCV

II

DCV I

ECV

LT

Evaporator

Heat pump mode

Gascooler/condenser II

Gascooler/

Condenser I

MT

Normal Cooling

Freezing

HP-Compressors

LP-Com-

pressors

EV

Gaskjøler FH

DCV III

HPV

T LT

T MT

P M

P H

P M

P L

T EV

T GCIT GCII

T GCIII

E HPC

E LPC

E Pump

E Fans

MP

V

LPV

CO2 refrigeration system superior to HFC systems in moderate and cold climates


Status CO2 commercial, centralised system

Field test system in Belluno, Italy 1999

Centralised system

Nominal cooling capacity 11 kW

Medium temperature (-10oC)

Heat rejected to liquid loop

Dry cooler on the roof

Preliminary COP 2.4 at 30oC amb

• More than 1500 supermarkets in Europe with transcritical CO2

• 10 kW to 1 MW• Systems have been

installed also outsideEurope

• What about hot climates?– Too low efficiency with CO2

or ….?


7

Typical efficiency at varying condenser/gas cooler air inlet temperature

More than 90% of operationCOP is important

Less than 10% of operationCapacity is important

Condenser/gas cooler air inlet temperature

CO

P

R-744

R-404A


One possible way:

Transcritical R744 refrigeration cycle

Using a two-phase ejector for expansion work recovery and the corresponding pressure-specific enthalpy diagram


Proposal for next generation of

R744 commercial refrigeration system

Advantages- pressure drop in the evaporator, simple valves

- good refrigerant distribution and slightly overfed evaporator

- robust and reliable arrangement

- lubricant management in separator © SINTEF 2012


More efficient components, a key for improved efficiency

Joint development project between SINTEF and OE

18-90m3/h R744 compressor [2012]

technische Daten

Höhe x Breite x Länge [mm] 500 x 440 x 830

Gewicht [kg] 286

Volumenstrom [m³/h] 18 - 90

Hubraum [cm³] 380

Max. el. Leistungsaufnahme [kW] 100

Drehzahl [min-1

] 800 – 4 000

Frequenzbereich [Hz] 53 - 267


1500 rpm

discharge pressure: 80 bar

superheat at the compressor inlet: 10 K

18-90m3/h R744 compressor [2012]

[%]


55

60

65

70

75

80

85

500 1000 1500 2000 2500 3000 3500

Ove

rall E

ffic

ien

cy [

%]

Revolution [rpm]

75bar

90bar

100bar

18-90m3/h R744 compressor [2013]Overall efficiency at varying speed, p0=35 bara


R744 Compressor and Component

Test Facility @ SINTEF


Conclusions

14

We need to reduce

and GHGemissions

• CO2 systems has been developed and commercialised for a lot of applications

• Development of more efficient components and work recovery concepts will enable competitive performance also at hot ambient conditions

• CO2 will together with the other natural refrigerants give a long term solution to the refrigerant transition


Thank you for your attention &

Questions are welcome!

[email protected]

This publication forms a part of the SINTEF – NTNU CREATIV project, performed under the strategic Norwegian research program RENERGI (195182/S60). The CREATIV is financially supported by the Research Council of Norway and several industry partners

mailto:[email protected]

Petter Neksa - Sintef Energy Research - ULTIMI RISULTATI NELLA REFRIGERAZIONE CON R744

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Transcript of Petter Neksa - Sintef Energy Research - ULTIMI RISULTATI NELLA REFRIGERAZIONE CON R744