Danfoss Cooling Danfoss Multi Ejector · Ejector is used instead of throttling device and it can utilize part of ... Commercial refrigeration R744 systems equipped with ejectors can

RC Business Presentation 1 |

Danfoss Cooling Danfoss Multi Ejector

www.danfoss.com


Transcritical Booster system most common CO2 systems

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R744

Aprx 7000 systems up today with Danfoss components ( 2000 has been count in 2015)


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Ambient temperature

Transcritical booster compared to R404A

Above 27oC is not efficient compares to R404A R404A is used as the benchmark for energy and CO2 booster system as benchmark for the swept volume of compressors

Transcritical Booster system Energy comparison

27 °C


Transcritical vs. Subcritical

Subcritical CO2

Transcritical & Subcritical CO2

Transcritical & Subcritical CO2

Subcritical CO2

Energy savings of

transcritical CO2 compared

to single stage R404A

Melbourne -4%

•Copenhagen 9% Paris 0%

•Rom -10% Seattle 3% Sapporo 3%

Cape Town -10%

•Buffalo 1%

RC Power Point Guideline 5 |

New technologies targeting efficient CO2 systems in warm climate

• Heat reclaim

• Parallel compressions

• Ejectors:

• Vapor ejector in DX system

• Liquid ejector in Flooded system

• Ejectors in flooded system

Evolution of Technology How can we move / remove the CO2 equator?


Parallel compression system

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R744

• Improvement of COP in warm climates • Reduction of swept volume of the compressors • Aprx 50 installations in 2014 and 200 in 2015


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Ambient temperature

Energy - Parallel compression compared to

R404A Crossing point moved from 27 °C to 38 °C

Parallel compression system

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Ambient temperature

Swept volume-Parallel compression compared

to Booster system

38 °C


What is an Ejector

• Expansion work recovery

Ejector is used instead of throttling device and it can utilize part of expansion work . The primary flow of the ejector (flow form Gascooler) drives the secondary flow (from the evaporator) and “pump” it up in higher pressure levels than suction pressure levels.

Which are the benefits

• First Cost savings

Lower cost compared to parallel compression trans critical CO2 racks due to lower swept volume of compressors. (i.e. smaller compressors or less number of compressors).

• Fast Pay Back – Energy saving

Improved COP, enhanced operation of parallel compressors and lower swept volume to the MT compressors ,result to lower energy consumption. Saving for End Users

Ejector! What and Why?

MT

LT

Ejector in the place of High Pressure valve


EJECTOR DESIGN - EJECTOR PRINCIPAL

Mixing chamber

motive nozzle

Suction port

Diffuser

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• Motive nozzle is connected to gas cooler. • Motive flow : high velocity

• Suction port to the evaporator outlet • low velocity, low pressure

• Motive flow is driving the suction flow, mixed in the mixing chamber. • Diffuser is use to recover pressure • The Exit of the ejector is connected to a receiver.


Let’s have a closer look How does it work?


EJECTOR IN THE SYSTEM ( with parallel compression) Transcritical operation

System with a medium pressure receiver and a receiver compressor to compress.

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MT

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EJECTOR IN THE SYSTEM ( with parallel compression) Subscritical operation

For ambient temperature is less that 21 oC ejectors are not efficient to pump and the system is operating as a parallel compressor system or a booster system (if receiver compressors are off)

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Ejector in a CO2 system

Pressure HP inlet 75-110 bar Pressure suction inlet

25-30 bar

Pressure outlet 32-37 bar

Typical working pressures

• Pressure difference between receiver and suction pressure is aprx 7 to 10 bar

• Ejector is “pumping” a part of the evaporated mass flow to the receiver pressure.


Mass flow distribution System operating with out parallel compressor and with out ejector (equivalent to booster system)

100%

55% 55%

100% 45%


• Booster system, not energy efficient for high ambient temperatures ( >27 oC)

• Illustration of transcritical operation (~33 oC ambient temp.)


Mass flow distribution System operating with parallel compressor but with out ejectors

100%

55%

55%

45%


• Parallel compressors, compresses gas from a higher start pressure and is therefore delivering a higher COP

• Efficient in higher ambient temperatures



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60% 60%

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Ejector in a CO2 system Mass flow distribution System operating with parallel compressor and ejectors

• Ejector is lifting a part of the gas from a low pressure to the parallel compressor suction pressure and enhancing the effect of the parallel compressor.

• Increased COP

• The Use of ejectors is a saving on swept volume of the compressor

• Energy saving in high ambient temperature

• Ejector operate efficiently for temperature >21 oC)

• Ejector may enable operation of parallel compressor at lower temperatures


80%


Ejector system

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Ambient temperature

Gas ejector high and low compared to R404A

Ej low 25%

Ej High 35%

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Gas ejector compared to Booster system

The energy saving a function of the ambient conditions and system design

Commercial refrigeration R744 systems equipped with ejectors can achieve COP higher than for conventional R744 systems (booster assisted by parallel compression) even by 20% at high ambient temperatures


Liquid ejector system Enable systems with flooded evaporators

GC

MT

* HP diagram from A. Hafner (SINTEf) presentation @ NorskKjøleteknisk Møte 2014

• Liquid ejector systems allow the MT evaporator to be flooded. • Ejector is used as pump for excessive liquid • System run with higher suction pressure. (increase saving) • Evaporation temperature is in average raised by 5K.

• Trials has been running since 2013 (ENEX)


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Gas ejector compared to Booster system

Ej low 25%

Ej High 35%-40%

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Ambient temperature

Gas and liq. ejector high and low

compared to R404A

Liquid and vapor ejector system

• There are few (3-4) stores operating in Europe (Enex) • Limited experience on the design and configuration of

the systems • Limited experience with case controllers • Technology currently not availed to other OEMs


Energy Efficiency

System Energy saving VS. R404a

Compressor saving VS. Booster

Booster -25% 0%

Parallel compression 3% 19%

Gas ejector 7% 28%

Liquid & gas ejector 16% 35%

Comparison made @ 40 °C

The energy saving a function of the ambient conditions and system design

System Energy saving VS. R404a

Compressor saving VS. Booster

Booster -11% 0%

Parallel compression 7% 15%

Gas ejector 10% 18%

Liquid & gas ejector 22% 27%

Comparison made @ 32 °C


• Parallel compression is not a possibility on small systems (<100kW)

• Large energy saving potential in warm ambient with ejector technology – COP can increased by ~20% compared to the parallel compression systems

• Liquid ejector solution is not ready for the large market yet. Better/optimal controller

are required.

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Capacity [kW]

Pack price comparison (estimate)

Booster pack [%]

Parallel compressionpack [%]

Gas ejector pack [%]

Gas and liq ejector pack

[%]

CO2 SYSTEMS Fist cost


EJECTOR IN THE SYSTEM ( Future simple system) Bringing the first cost down

1

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• Targets low first cost for small to middle size installation

• Danfoss is working towards that technology.

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Capacity [kW]

Pack price comparison (estimate)

Booster pack [%]

Parallel compression pack [%]

Gas ejector pack [%]

Gas and liq ejector pack [%]

Simple pack [%]


Danfoss Multi Ejector

Documents

Danfoss Cooling Danfoss Multi Ejector · Ejector is used instead of throttling device and it can utilize part of ... Commercial refrigeration R744 systems equipped with ejectors can