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AIRAH - Chilled Water DiscussionAIRAH Chilled Water DiscussionTuesday 13 November 2012Phillip Carruthers

Viable RefrigerantsHCFC – currently at 65% phase out but 95% in 2015

HCFC22HCFC22 – Packaged plant– Packaged reciprocating chillers– Builtup DX refrigeration plant

HCFC123 (replaced CFC11, CFC113, & CFC114)– Low pressure centrifugal chillers

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Viable RefrigerantsHFC – Not yet mentioned but Carbon Tax levies has hit them hard.

HFC134a (CFC12 replacement)Normal temperature refrigeration (replaced CFC12)– Normal temperature refrigeration (replaced CFC12)

– Centrifugal chillers – Screw chillers – Scroll chillers – Packaged plant

HFC407c (HCFC22 replacement)– Screw chillers– Packaged plantg p

HFC410a– Usually small packaged plant

Carbon Tax levy is $23/equivilent tonne CO2/kg as from 1 July 2012

Viable RefrigerantsNatural Substances

Ammonia – scary to some because they don’t understand it!Ammonia – scary to some because they don t understand it!– Zero impact upon the environment– Stinks which is a problem – Plantrooms are Engine Rooms and must be freely ventilated– Very efficient and cheap– 1kg absorbs into 1kg of water.

CO l t f i tiCO2 – low temp refrigerationPropane – careful! Used in all new refrigerators built in Europe.– There are refrigerants on offer but look at them closely!!!!!

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Anything New????HFO – Hydro-fluro-olefin

They are coming and in some cases there’s here! 0 ODP and minimal GWP1234yf replaces 134a in automotive AC in Europe

Refrigerants - CommentsHCFC’s

No new equipmentReplace old equipment that failsAdvise replacement prior to 2015

HFC’s134a is okay in most applications407c is a blend and cannot be used in a flooded evaporator. If it leaks the whole charge has to be replaced.410a is high pressure and should be used with caution. g pCarbon Tax levies will hurt. (over $200/kg)

Ammonia Give it a go in packaged chillers.

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Recognising Chillers

Centrifugal Chillers

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Centrifugal ChillersUsually flooded evaporatorDo not like high head pressure

Hi h iHigh pressure surge is scaryCW water temperature is critical and should be as low as possible

BUTThere must be a differential between CHW temp and CW Temp to maintain a positive pressure across the impellor– Need 4OK to 8OK approach from LCHW Temperature dependant upon manufacturer

Surge occurs when the pressure across the impellor is low meaning there is no lift.Lift is the difference between entering pressure and leaving pressure and is affected b i ll d V i bl d hi b bl if t t ll dby impellor speed. Variable speed machines can be a problem if not controlled properly.

Centrifugal Compressor

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Centrifugal Compressor Hermetic

Centrifugal Compressor Open drive

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Magnetic Bearing Centrifugal Chiller

Magnetic Bearing Compressor

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Helical Screw ChillersCan be flooded or DX but usually floodedDoes not like short cycling on low loadDoes not like short cycling on low load

Oil transfer is by pressure difference only (no pump)Frequent starts will transfer oil out of compressorWill not handle low loads (don’t believe claims of 15%)Head pressure critical. Must remain at designCW should be at 29.5oC. Will not start with low CW temperatureCW should be at 29.5 C. Will not start with low CW temperature– Need about 18oK approach from LCHW Temperature.

Capacity control is usually four steps but can be infinite.

Helical Screw Compressor (Fixed Speed)

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Helical Screw Compressor (Fixed Speed)

Screw Capacity Control

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Helical Screw Compressors

Air Cooled Chillers

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Scroll CompressorsDX evaporators alwaysOne compressor one step of coolingOne compressor one step of cooling.

Digital compressors an internal unloading facility that modulates flow by a solenoid valve

Usually HFC407c refrigerant but HFC134a is also usedAre subject oil failure under repeated low load starts.

Scroll Compressor

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Pipework – There Are Questions To Answer

Chiller Connections – What might they be?

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Headers - Is there a problem here?

Pump Connections – Is there a problem?

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Flow Pipework – Is there a problem here?

What th’ ?

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Condenser Water Pipework – Problem?

Catastrophe

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Headers – Problem????

Why is this a problem?

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Why is this a problem?

Some Results