The compressor is commonly described as the ‘ engine ’ or ‘ heart ’ of a refrigeration system , with the refrigerant being the blood .
INCORPORATING COLD CHAIN
FEATURE
Compressors – the heartbeat of refrigeration By Eamonn Ryan
The compressor is commonly described as the ‘ engine ’ or ‘ heart ’ of a refrigeration system , with the refrigerant being the blood .
Compressors are mechanical devices used to increase pressure in a variety of compressible fluids , or gases – and in the case of HVAC & R equipment , to phase shift refrigerants for air conditioning and refrigeration . They come in a number of designs – the main ones being reciprocating , screw , scroll and centrifugal . The right choice depends on the operating environment , load and other design factors .
Hennie Basson , managing member of Coldfact , explains the key the key considerations when it comes to selecting a compressor as being , “ the capacity of the compressor , type and range : whether screw , scroll or centrifugal ; compressor operating pressures and temperatures ; energy efficiency ; and also the physical size or dimensions of the compressor ”.
Daniel de Beer , sub-Saharan Africa regional manager for Copeland , in turn lists the most important factors to consider when selecting a compressor for a specific application as being : efficiency , cost , availability , warranty and aftersales support . “ A more efficient compressor can help reduce energy consumption and operating costs . It is important to consider the overall cost-effectiveness of the compressor , considering factors such as energy efficiency , maintenance requirements , and expected lifespan . It is important to choose a compressor that is readily available in the market and supported through a reliable supply chain . It is also wise to consider the length and coverage of the warranty when selecting a compressor , as it can help protect against unexpected repair or replacement costs . Aftersales support must include technical support , maintenance , and repair assistance provided by the manufacturer or authorised service centers . It is important to choose a compressor from a manufacturer that offers reliable aftersales support to ensure prompt resolution of any issues that may arise ,” he expands . These factors play a crucial role in selecting a compressor that meets the specific requirements of an application while providing optimal performance , reliability , and cost-effectiveness .
The commercial refrigeration industry has changed drastically in recent years along with changes in customer requirements . Customers today demand an everwidening spectrum of applications , from large centralised systems to small walk-in freezers and coolers . Energy efficiency and environmental sustainability have become business priorities . And digital technologies promise connected , predictable visibility to refrigeration systems . These all affect the compressor market .
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The BITZER Ammonia Compressor Packs ( ACPs ) for industrial refrigeration .
UNPACKING SCROLL COMPRESSORS
De Beer says that Copeland has a rich history of innovation and development , having been at the forefront of compressor technology for 102 years . They introduced the first semi-hermetic and hermetic compressors in the 1940s and 1950s , followed by the high-efficiency Discus semi-hermetic , air conditioning , and heating scroll compressors in the 1980s and 1990s .
Copeland semi-hermetic compressors were the first to successfully operate with an electric motor inside the compressor casting in 1941 . Building upon that success , Copeland advanced the industry with its Copeland Scroll technology launched in 1987 .
A scroll compressor is a type of compressor that uses two interleaved spiral-like scrolls to compress refrigerant . It is a hermetic compressor , meaning that it is completely sealed and does not allow any air or pressure to escape . A hermetic scroll compressor is highly compact - as the compressor and motor are placed on a single shaft and sealed together .
The coefficient of performance ( COP ) of a scroll compressor is generally higher than that of a semi-hermetic compressor , says De Beer . This is because scroll compressors have fewer moving parts and are more efficient at compressing refrigerant gas . Additionally , scroll compressors have less leakage and lower friction losses than semi-hermetic compressors , which further improves their efficiency .
“ We are seeing a lot more scroll technology adoption within the marketplace ,
AHI-Carrier where people see it as a cost effective and efficient solution ,” he adds .
Copeland manufactures various types of compressors : “ We make small hermetictype compressors similar to that used in a domestic refrigerator , but larger applications as well . We also do semi-hermetic and screw compressor technology , which is where most of the market is positioned . None of that technology is new , having started in the 70s and 80s .
“ On top of that we developed the scroll technology – and this has been acquiring a share of the refrigeration market for the past 15 years or so to achieve a dominant position as people have transitioned from semi-hermetic to scroll compressors in other markets , while it is now gaining traction in the MEA ( Middle East and Africa ) region . While its relatively new here , it is by no means a new technology and something that certainly is not new for us ,” says De Beer . “ The main driver of scroll adoption is the fact that we use this technology in our ZX condensing units . The overall market adoption of our ZX range has put us in a leading position within this segment , where we use scroll technology . This drove adoption as more installers and end-users got familiar with the exceptional reliability of this technology . In addition to this , ongoing innovation has now expanded scroll technology into the hydrocarbon and
CO 2 market space , with capacity ranges up the 30HP .”
He argues that scroll compressor technology is by far the best in class from a COP perspective - its space and weight requirement takes approximately 30 % less space within a unit .”
He lists one of its greatest efficiency boosters as being the use of Copeland ’ s Enhanced Vapor Injection ( EVI ) with the sub-cooling of the liquid before it gets to the plant , making it a lot more efficient . An intermediate pause on a scroll compressor allows gas bypass from the intermediate compression chamber to the discharge side . This technique helps reduce overcompression loss and maintain high efficiency over a wider compression ratio range . This sub-cooling process uses some energy but increases the capacity of the compressor by 30 to 40 %. “ From a COP perspective , this is far superior over other technology .”
The Carrier 19DV centrifugal chillers are the only chillers fitted with a new type of compressor design .
COLD LINK AFRICA • November 2023 www . coldlinkafrica . co . za 17