Technical refrigerants are required , excess heat is available and grid congestion occurs .
This is especially important as the industry transitions from ozone-depleting refrigerants to those with low global warming potential ( GWP ). Natural refrigerants , including those that use water , have low to no GWP .
FLEXIBLE USE , OPERATING RANGE AND ENERGY SOURCING The evolution of absorption cooling technology has resulted in much greater application versatility for industrial process cooling installations . Absorption chillers have been successfully applied for gas turbine inlet air cooling applications , hazardous-area
outdoor applications and other uses .
Although absorption chillers are typically longer and heavier than electric centrifugal chillers , it is possible to adjust the dimensions and achieve the same cooling capacity . This can help solve installation challenges such as in tight spaces or other physical constraints that factor .
A revolutionary development in LiBr absorption chillers is that they can offer temperatures as low as -5 ° C .
EASE OF OPERATION AND MAINTENANCE One of the most common misconceptions about absorption chillers is that they are not easy to operate or maintain because the lithium bromide salt solution crystalises . The truth is that modern absorption chillers are equipped with PLC controls that ensure the concentration percentage of the operating lithium bromide solution does not enter the crystallisation zone .
" There is a misconception about the efficiency , flexibility , and maintainability of absorption chillers ."
The design method used can offer further protection against crystallisation . For instance , one method uses a combination of two-step , evaporator-absorber and parallel ( lithium bromide ) flow design instead of a series-flow or reverse-flow design . In this two-step design , the entering absorber spray concentration is usually only 58 to 61.5 percent , depending on the type of unit and design condition . Besides low solution ( salt ) concentration , the unit operates with the lowest temperature and pressure in the first stage ( high temperature ) generator section .
This type of low solution ( salt ) concentration cycle provides protection against crystallisation . It also can improve the reliability of the system and extend its life by reducing corrosion and the amount of non-condensable gases .
To determine the topping quantity of the corrosion inhibitor , the lithium bromide sample should be analysed once or twice annually based on the frequency of operation . A thorough understanding of the cycle is vital for successful operation and maintenance , in accordance with a manufacturer ’ s guidance .
Just like any other water-cooled chiller , cooling ( condenser ) water quality must be maintained in accordance with the manufacturer ’ s guidelines . The vacuum also requires maintenance ; however , modern absorption chillers have an automatic purge system that performs this service .
With modern controls and well-considered designs , absorption chillers are straightforward to operate and maintain .
In water cooled solutions , a cooling tower is hidden but heavy cost . More than electricity , this equipment costs water . On average , a cooling tower evaporate 10 % water to the atmosphere . This is a considerable volume and recurring cost .
Allow me to explain this with an example of a hot water fired absorption chiller with cooling capacity of 580kW . This machine will use 180 m 3 / h cooling water and evaporate 18 mm 3 / h to the atmosphere .
Roughly R1 000 / hour will be the estimated expense of such a cooling tower , for 8 hours per day and 24 days a month ; monthly – the water expense can be R 19 200 .
A solution we offer to our clients is the use of a water-to-water heat exchanger . With this technology we are able to replace air cooled cooling towers . In this , heat is transferred to water rather than air . No condenser fans required , no evaporation of water at all . A great saving on recurring expense .
To summarise this example in simple terms – 580kW chilled water generation using a generator ’ s jacket water ( 63 m 3 / h ) consume 3 kW electric power . To pump borehole water and circulate chilled water to the building addition 20 to 27kW electric power may be used , while 0 m 3 / h will be the water consumption . 600kW cooling capacity using 30kW electric power .
In conclusion , the time has come to see what absorption chillers really offer . Facilities searching for a chiller that makes
www . refrigerationandaircon . co . za RACA Journal I January 2023 49