Essentials
By Selele Mashilo
SELELE MASHILO
Selele Mashilo has a mechanical engineering diploma from Tshwane University of Technology and a refrigeration and air-conditioning diploma from Unisa . His experience includes over a decade in government as deputy-director building services before rejoining the private sector in 1998 as HVAC & R project engineer . He is the former chairperson of the Refrigeration and Air Conditioning Empowerment Forum of SA ( RAEFSA ), the Air Conditioning and Refrigeration Industrial Council of SA ( ACRICSA ), and Black Energy Services Companies ( BESCO ).
WATER TREATMENT IN AC SYSTEMS
Water is sometimes used as a secondary refrigerant in air conditioning , or it may be used in cooling towers for cooling purposes .
For cooling , water is mainly used in evaporative cooling systems . It plays a very important role in air conditioning , but it does not always come in a perfect condition as expected . It is water that contributes to corrosion of metals and can also react with other elements .
Water in air conditioning installations must be suitably treated to avoid calcium deposits on the surface of metals . The calcium deposits reduce heat transfer by cooling towers which may create system-tripping at high pressures . Material selection is therefore very important when being applied in air conditioning systems , and in various locations .
We are going to come across various terms in the field which define water treatment – knowledge of these makes it easier for one to understand the scientific approach required for water treatment . It is thus beneficial to look at the theory in application to realise the need for water treatment in these systems .
The result of poor water quality in water circuits is that metals used in most plants may be destroyed and thus shorten the lifespan of the plant . Water may be alkaline ; which is the sum of dissolved chemical bicarbonate , carbonate and hydroxide salts . The amount of dissolved calcium and magnesium in water determines its hardness . There might also be biological deposits in water like algae and slimes .
The pH value , or the logarithm of the reciprocal of the hydrogen ion concentration , which determines the acidity or alkalinity of water , may be too high or too low .
Water sludge formations , which are sedimentary water formed deposits , should be prevented . Water-formed deposits are also always found in the system where water is in contact with surfaces .
It can thus be deduced , that because of the various affecting factors that water in air conditioning systems can produce , treatment is required for both interior effects on the metals in a system , as well as corrosion which attacks the metal ’ s external surfaces . RACA
REFERENCES :
1 . ASHRAE
An Art student , sick of working at a fast food cafe for what had seemed an eternity , decided to get a job working as a labourer at a construction site . Being an over-confident Art student , he soon began to brag to the other workers about all sorts of things .
One day he decided to brag that he could outdo anyone in a feat of strength . He made a special case of making fun of the engineer on the site . After several minutes , the engineer had had enough .
HUMOUR
" Why don ' t you put your money where your mouth is ?" asked the engineer . " I will bet a week ' s wages that I can haul something in a wheelbarrow over to that outbuilding that you won ' t be able to wheel back ."
" You ' re on , little guy !" the braggart replied . " Let ' s see what you have !"
The engineer reached out and grabbed the wheelbarrow by the handles . Then , nodding to the young man , he said , " All right . Get in ." RACA
www . hvacronline . co . za RACA Journal I May 2021 45