Technical
NATURAL REFRIGERANT- BASED CHILLERS
By Arshad Ali Khan , managing director at EHVAC
As fewer and fewer CFCs and HCFCs are available for use as refrigerants , companies are looking to natural options as a more effective replacement . This article is based on a technical talk with SAIRAC members .
On the one hand fossil fuels and Chlorofluorocarbons ( CFCs ) that are synthetic gases used in Air conditioning , have brought us to the stage we find ourselves today . Global warming has resulted in the average earth temperature increasing abnormally . Extreme heat or cold spells are breaking records year after year too and so the time is now to look to renewable energy and natural gases for air-conditioning systems .
On the other hand , we have a totally natural gas that can be used as an efficient refrigerant as remedy to this problem we have , it is called Ammonia .
WHY IS AMMONIA GROWING IN POPULARITY ? According to The American Society of Heating , Refrigerating and Air-Conditioning Engineers ( ASHRAE ) and the International Institute of Ammonia Refrigeration ( IIAR ), ammonia is a costeffective , efficient alternative to CFCs and HCFCs that is also safe for the environment .
Ammonia ( NH3 ) is a gas comprised of two elements — nitrogen and hydrogen . Whether found in nature or made by man , ammonia is colourless but has a sharp , pungent odour . Ammonia , that is frequently used commercially in large freezing and refrigeration plants is also called ‘ anhydrous ammonia ’ because it contains almost no water ( it is 99.98 % pure ). Household ammonia , by comparison , is only about 10 % ammonia by weight mixed with water . 1 . As a refrigerant , ammonia has four major advantages over
CFCs and HCFCs :
2 . An ammonia-based refrigeration system costs 10-20 % less to build than those that use CFCs because narrower-diameter piping can be used .
3 . Ammonia is a 3-10 % more efficient refrigerant than CFCs , so an ammonia-based system requires less electricity , resulting in lower operating costs .
4 . Ammonia is safe for the environment , with an ozone depletion potential ( ODP ) rating of 0 ( zero ), and hence zero global warming potential ( GWP ).
5 . Ammonia is substantially less expensive than CFCs or HCFCs .
Zudek
The latest air-cooled ammonia chiller – the Airmatik .
There are however two key disadvantages to using ammonia as a refrigerant : 1 . It is not compatible with copper , so it cannot be used in systems with copper pipes .
2 . Ammonia is poisonous in high concentrations . Two factors , however , mitigate this risk being ammonia ’ s distinctive smell is detectable at concentrations well below those considered to be dangerous , and , ammonia is lighter than air , so if leak occurs , it will rise and dissipate in the atmosphere where there is no further harm to the environment .
After years of research , curiosity and testing , Zudek ( Italy ) came up with an air-cooled ammonia chiller with aluminium microchannels that is efficient , reliable and compact . EHVAC has introduced the world ’ s first air-cooled chiller that offer a COP of 4.14 to the South African industry . It is called Airmatik . The system offers : Microchannel condensers - the best technology currently available with aluminium microchannels , ensure the maximum heat exchange and very low ammonia levels . Each condenser can be individually partitioned .
Condenser fans are 1600mm diameter , the large diameter of the fans guarantees low energy consumption for ventilation and 2.1k We for every 100kW of heat with quiet operation .
www . hvacronline . co . za RACA Journal I April 2021 45