ammonia as a refrigerant in the water chiller for apple storage cooling

Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning

ANNUAL MEETING OF THE

Belgrade, May 10, 2011 Slobodan PejkovićAmmonia as a Refrigerant in the Water Chiller for apple storage cooling

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ANNUAL MEETING OF THEREGIONAL OZONE NETWORK

FOR EUROPE & CENTRAL ASIABELGRADE, SERBIA, 10 -13 MAY 2011

Case study:Ammonia as a Refrigerant in the Water

Chiller for apple storage cooling (cold storage capacity is 8000 t)

Dipl.-Ing. Slobodan Pejkovi ć

Filter Frigo - Serbia


[email protected]


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For chilling and storing apples, cooling installationhas been planned with water chiller using Freon 404Aas a refrigerant, and cools secondary fluid, mix of waterand glycol to -6ºC temperature and lower. Advantageof the secondary fluid is the possibility of temperaturecontrol in cold storages with small difference betweenthe air and secondary fluid’s temperature. In this way


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the air and secondary fluid’s temperature. In this wayloss in weight of products is decreased. Besides that, itis also important that the quantity of a refrigerant insuch cooling systems is small.

Necessary cooling capacity for cooling and storing8000 tons of apples is around 1.1 MW.


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4Belgrade, May 10, 2011 Slobodan PejkovićAmmonia as a Refrigerant in the Water Chiller for apple storage cooling

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Freon 404A as three component mixture of arefrigerants R143a / R125 / R134a has high globalwarming potential (GWP=3780). Therefore in theEuropean Union measures are contemplated whichwould lead to decreased use of this refrigerant. Thefirst of the measures introduced by Denmark since2011 is ecological tax for use of Freon 404Aamounting to 79€/kg, which shall be collected during


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amounting to 79€/kg, which shall be collected duringFreon procurement.

That made us think of envisaging some of thenatural refrigerants for this cold storage. The choice

was ammonia.


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Ammonia as a natural refrigerant has GWP=0,meaning that it does not influence global warming ofthe Earth, therefore its use is being stimulated.Advantages in using ammonia with strong smell is thatduring leakage which happens occasionally in coolinginstallations is that you can immediately sense it,


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installations is that you can immediately sense it,remedy the failure and top-up the installation withrefrigerant without stopping. Differently from that,Freons, even R404A are without smell and its leakagefrom the cooling installation can not be observed untilpressure drops, that is, capacity decreases.


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Because R404A is three-component mixture ofdifferent Freons, in case of leakage one mustdischarge the whole quantity from the installation(installation charge is around 300 kg), the failure mustbe remedied, than the installation should be vacuumed


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be remedied, than the installation should be vacuumedand refilled. This procedure requires several hourswork and during that period the cooling installation cannot operate.


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Ammonia as a refrigerant is cheaper. Exploitationcosts and maintenance costs of modern ammoniainstallations are lower than for Freon installations.

Installations with ammonia as a refrigerant aremore energy efficient, meaning that for achieving the


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more energy efficient, meaning that for achieving thesame cooling capacity they shall spend lesselectricity. Due to poor mixing with oils for lubricatingcompressor, ammonia can be used in floodedevaporators at higher evaporating temperatures inrelation to Freons, simultaneously using lesselectricity.


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In order to achieve the necessary glycoltemperature of -6ºC with ammonia as a refrigerant,the compressors can work with evaporationtemperature of -10ºC in flooded plate&shellevaporator and with suction gas superheat of 1K.

In order to achieve the same conditions (glycol


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In order to achieve the same conditions (glycoltemperature and capacity) with Freon R404A as arefrigerant, the installation must have an directexpansion evaporator where the evaporationtemperature can not exceed -12ºC while suction gassuperheat must be from 6 to 10K.


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Bitzerscrew

compressor

Ammonia R717 Freon R404A

Cooling

capacity

[kW]

Power

Consumption

[kW]

Energy Efficiency

Ratio

EER

Cooling

capacity

[kW]

Power

Consumption

[kW]

Energy Efficiency

Ratio

EER

Model OSKA8581-K

324 83.4 3.88 293 94.7 3.09


In order to present real difference between the ammonia and Freon404A installations, we shall present table with the cooling capacity and powerconsumption of screw compressor, product of Bitzer.

OSKA8581-K

Bitzerscrew compressor

Ammonia R717 OSKA8581-K

Freon R404A OSKA8581-K

Evaporation Temperature [°C] -10 -12

Condensing Temperature [°C] 35 35

Liquid Subcooling [K] 3 3

Suction Gas Superheat [K] 1 10


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Operating regimes

Tables show that in installations using ammoniaas a refrigerant for the same compressor model,cooling capacity is 10% higher in relation to R404Awith smaller absorbed power for 11.3 kW.

During the first 27 days of work of the coldstorage with full capacity, when the daily apple intakeexceeds 300 t/day, electricity savings during work of4 screw compressors, products of Bitzer, model


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4 screw compressors, products of Bitzer, modelOSKA8581-K with ammonia as a refrigerant would be29 MWh. Simultaneously, these compressors wouldhave 10% higher cooling capacity than the Freonones, and would enable quicker cooling of apples,which is very important for apple quality.


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Analyses of different solutions using ammoniahave been made. One of the solutions was a chillerwith one screw compressor of 1150 kW coolingcapacity. Maximum cooling capacity for this type ofcold storage is necessary during the first 30 days ofwork, from start of apple picking. After that, needs forcooling decrease, as well as the external temperature,


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cooling decrease, as well as the external temperature,and the water chiller has better condensing conditions.Therefore a solution with three water chillers has beendiscussed – chillers in variant 1 with water cooledcondenser, and in the variant 2 with air cooledcondenser. Both solutions have their advantages andshortcomings.


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Advantage of the chiller with air cooledcondenser is installed in the container outside the coldstorage facility, so no special safety measures arerequired. Besides that, apples are stored in the periodfrom October to June, when we don’t have extremely


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from October to June, when we don’t have extremelyhigh air temperatures, and the condensingtemperatures are such that they render sufficiently highEnergy Efficiency Ratio – EER.


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Microchannel Condenser


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AUTOMATIC OIL RECOVERY SYSTEM

For a regular, efficient and continuous operation of a chiller, it’s necessary to guarantee oil recovery to the compressor.

Oil often collects in the bottom part of the


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Oil often collects in the bottom part of the evaporator, with the risk to compromise efficiency and heat exchange of the evaporator. For this reason an oil recovery system has been introduced; thanks to an ejector, oil at low pressure is conveyed from evaporator, with high pressure ammonia to the compressor suction.



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Unit prices for the equpment:

� Ammonia water chiller; piston compressor,water cooled condenser - - - - - - - - - - - - - - € 135.000

� R134a water chiller; 2 Turbocor compressors,


� R134a water chiller; 2 Turbocor compressors,water cooled condenser - - - - - - - - - - - - - - € 92.000

� R134a water chiller; 2 screw compressors,water cooled condenser - - - - - - - - - - - - - - € 59.000

� Cooling capacity 400 kW


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Price for the cooling system:

� R404a glycol chiller system;cooling capacity – 1.200 kW4 screw compressors,


4 screw compressors,1 evaporative condenser

for 4 compressors € 260.000


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CONCLUSION Advantages of ammonia as a refrigerant:� Ammonia as a natural refrigerant does not influence global warming of

Earth.� Ammonia as a refrigerant is cheaper than Freon.� Exploitation costs and maintenance costs of modern ammonia installations

are lower than for Freon ones.� Installations with ammonia as a refrigerant are more energy efficient.


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Shortcomings of ammonia as a refrigerant:� Investment costs in making ammonia installations significantly exceed the

costs of making Freon installations.� Safety measures that should be undertook in using ammonia installations

due to its explosiveness cause fear with investors and influence the final price of the installation.


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Thank You For Your Attention


Question?


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Question?

ammonia as a refrigerant in the water chiller for apple storage cooling

Technology

apple storage cooling

water chiller

cooling installation

necessary cooling capacity

cold storage capacity

c temperature

freon installations

freon r404a