Feature capacities ranging from 118kW to 914kW . R32 refrigerant is also commonly used adding to the aforementioned .”
AHI Carrier Trane / Service First
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Every Carrier chiller installed today is connected to the Carrier Smart Service and provides their customers with 24 / 365 visibility and trending .
A hybrid chiller installed at a filling station in Kwazulu-Natal .
circuit which is then in turn cooled by a cooling tower ,” says Deo du Plessis , associate at Spoormaker and Partners .
“ While you might think that an air-cooled chiller should offer better savings as heat rejection is direct , a water-cooled chiller is in fact more efficient . There are various reasons for this but the two most important are ( i ) water is more efficient at taking away heat and ( ii ) a cooling tower approaches the wetbulb temperature while an air-cooled chiller approaches the drybulb temperature ,” adds Hattingh .
Water-cooled plants are generally more complex , since they require cooling towers , water treatment , separate real-estate locations for the chillers and cooling towers , but are popular for large cooling applications ( big buildings , process cooling , mine air cooling ) due to their superior efficiency . These chillers use HFC ( R134a ), HFO ( R1233zd , R514b ) and Ammonia .
Roelofse ’ s comment concurs with Hattingh on large applications . “ Water cooled chillers are suitable in cooling capacities ranging from 12kW to 9MW , and then heating
RACA Journal I March 2021
• Adiabatic systems for chillers Adiabatic systems are employed on air-cooled chillers , by evaporatively pre-cooling the air entering the condenser , either by water sprays or wetted pads .
“ This chiller type offers a pretty neat way of both saving water and electricity during peak load demands ,” Hattingh notes .
While adiabatic systems work very well on cooling towers they have some draw backs when it comes to chillers , as most systems are retrofitted . Good water quality and careful design is required to ensure these systems continue to perform as intended .
• Absorption chillers “ The free lunch ! While these units are often perceived to provide ‘ free ’ cooling there are a couple of provisos that apply . Cooling can be obtained cheaply only if there is a waste source of heat and if cooling water is abundant ,” says Hattingh .
An absorption chiller doesn ’ t use a compressor to drive the refrigerant circuit but rather uses a chemical process . Heat and cooling are used by various heat exchangers to achieve the same end result as any other chiller ( cold water ).
But there is a small catch . The process is somewhat inefficient ; meaning a large amount of heat is required to provide a certain amount of cooling . This heat has to be dispensed along with the building ’ s heat , in the cooling towers . What this means is that an absorption chiller generally requires a cooling tower that is twice as big as a conventional water-cooled chiller ’ s cooling tower ( and therefore uses about double the amount of water ).
SOME PROS AND CONS OF EACH CHILLER TYPE :
• Air cooled chillers “ Air-cooled systems are increasingly being used . Originally this was primarily because water is not consumed , but efficiencies of air-cooled systems have improved significantly over the past few years with new technologies such as variable speed compressors , frictionless bearings , smart controls , and so on . The main drawback in some applications is reduced life expectancy such as in coastal or aggresive atmospheric environments ”, says du Plessis .
Hattingh adds , “ air-cooled chillers make for simple installations but they also have some practical limitations . For medium-sized buildings or applications , air-cooled chillers can be ideal . They are also well suited for areas where there isn ’ t an abundance of water . For large facilities air-cooled chillers require significant real estate and the number of units becomes impractical .”
“ On the pro-side , air cooled chillers don ’ t typically require an internal plant room , have simplified water piping runs ,
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