Feature
CHILLERS : OVER A HUNDRED YEARS IN THE MAKING
Compiled by Benjamin Brits
Most processes today involving mechanical elements generate heat as a by-product , and if not removed from the system will result in unfavourable conditions .
No matter if you are looking at a processing plant , manufacturing facility , laboratory , or the cooling in a building , a version of the chiller would be a suitable solution in managing the various ways heat is generated that causes , amongst others , a negative effect on efficiency , comfort in the case of occupied spaces , and can ultimately cause varying degrees of system failure .
Chiller technology itself is by no means anything new and the first patented centrifugal water chiller dates back to 1921 . With the development , trials and errors involved in getting a new system to a patent stage , it means that the product has stood the test of time ; having already remained relevant for over a century .
CHILLER TYPES AND RESPECTIVE APPLICATIONS ( RELATED TO HVACR ) “ Chillers are classified by the way in which they reject heat . Heat rejection is necessary in order to satisfy the laws of ‘ give and take ’ ( or energy conservation ). Since heat is ‘ taken ’ from the building , space , or process that is being cooled , it must be ‘ given ’ to the outside air . The emphasis here is on heat , not on air . We don ’ t take the air from the building and dump it outside . Although that could provide some cooling , that is not the principle behind a refrigeration / cooling unit . All refrigeration units work on the same basic principle ( refrigeration cycle ), from a water chiller to basic air conditioner or even a fridge . Where and how the heat is dumped and how the refrigeration circuit is driven is where the differences lie ,” says Russell Hattingh , Pr . Eng . at BBE Consulting .
• Air-cooled chillers Air-cooled chillers simply reject transferred heat directly to ambient air via air-cooled condensers .
Today ’ s air-cooled chillers use mechanical compressors to drive the refrigeration circuit ( they are vapour compression type units ). ( Note the distinction made with reference to absorption chillers further along in the article .)
Hattingh notes , “ An air-cooled chiller uses fans to directly cool their condensers , or to reject heat . Hot refrigerant flows through a radiator type coil , which could be microchannel or conventional
© RACA Journal | Benjamin Brits
tube-and-fin . Fans ensure the removal of the heat from the coils . Air-cooled chillers are self-contained units and make for a relatively simple installation . These chillers will typically use screw or scroll compressors and HFC ( R134a , R410 ), HFO ( R32 , R1234ze , R454b ) or HC ( propane ) refrigerants .
Air cooled chillers typically support cooling capacities ranging between 5kW to 2MW and in addition to screw and scroll compressors , Ian Roelofse , industrial segment manager at Daikin South Africa adds swing compressors to the list . These compressors types being available with or without inverter capacity control .
Roelofse further says , “ The evaporators in chillers are generally brazed plate heat exchanger or shell and tube ( direct expansion ). Efficiency can vary between standard , high or premium options – similar to the model of car you buy – for the extras you pay extra , and these could include things like reduced sound levels , heat recovery options and heat pump compatibility versions .”
• Water-cooled units The main types of water-cooled units use screw and centrifugal compressors , which would also be classified as vapour compression . “ Water-cooled chillers reject the heat transferred from the cooled medium ( usually water ) to a condenser water
Here , three 250kW water chillers are installed atop an office building .
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