FEATURE
INCORPORATING COLD CHAIN
BITZER Supplied by Hennie Basson .
The BITZER CKHE7 CO 2 compressor for large capacity trans-critical applications .
Modulation technologies in scroll compressors is another technology that De Beer describes as having been around for some years . According to Copeland ’ s website , it allows systems to run at varying capacities to meet cooling demands . These technologies offer several benefits , including increased temperature control , less dehumidification , higher efficiency , reliability , and comfort .
In commercial applications , modulation technologies enable cooling systems to adjust capacity as needed . These technologies include multiplexing , variable speed systems , and modulating compressors with 10-100 % modulation capabilities . They provide flexibility in meeting cooling demands while reducing energy consumption .
Digital modulating scroll compressors feature infinite capacity control between 10 % and 100 %. An internal unloading mechanism opens a bypass port or vent at the end of the first compression pocket , allowing the compressed gas to be vented into the beginning of a suction pocket within the scroll . When the bypass port is opened , the effective displacement of the scroll is reduced to 0 %, and when it is closed , the scroll operates at 100 % capacity . The adoption of this technology has surpassed that of the use of variable speed drives ( VSD ). This is mostly driven by the simplicity of the technology , where you only have a coil which is either energised or not . Should one have a coil failure , the compressor maintains 100 % capacity .
These modulation technologies have become increasingly important due to government mandates around the world for energy-efficient cooling systems and the phaseout of refrigerants like R-22 . They
One of the first compressors from Bundesfachsule Kaiti Kilma Technik Museum , Frankfurt , Germany . offer improved efficiency and performance for both residential and commercial applications .
Compressor installation and maintenance come with some associated safety hazards . De Beer explains that the use of natural refrigerants has increased risks associated with installations and maintenance . “ This can easily be mitigated through ongoing training and development programmes , which the industry needs to invest in .”
There are seldom failures when it comes to installing Copeland compressors . Where there are , De Beer says : “ We find that most issues and failures can be prevented through proper installation and commissioning practices . Compressors are not made to fail , and a well-installed and properly maintained compressor will outlast most of its applications .”
He notes that compressors are becoming increasingly energy-efficient and environmentally friendly : “ We drive constant innovation throughout our product range and our compressors technologies are best in class . We utilise our global footprint and our extensive regional distribution network to drive customer support . In addition to this , we constantly invest in training , which we found to be the best tool to support our techno-savvy contractor base in the sub- Saharan Africa region .”
DIGITAL UNLOADING
De Beer lists newer innovations to the technology as being the use of smart controls in the compressors .
“ In South Africa , the energy crisis has prompted companies to seek different types of modulating technology as well . Even though variable speed technology exists , it adds complexity to a design by requiring an electrician – and so in South Africa we have shifted more and more towards the use of digital unloading for modulation which is a simpler , mechanical means of reducing load from a compressor as opposed to the use of VSD .”
Digital unloading is a method used to
control the capacity of a compressor . It is
Sabroe an alternative to using VSDs in certain compressor applications .
VSDs are commonly used in compressors to control the speed of the motor , which in turn controls the capacity of the compressor . By adjusting the motor speed , VSDs can modulate the output of the compressor to match the demand for compressed refrigerant . This allows for energy savings and improved efficiency , as the compressor only operates at the required capacity .
Digital unloading , on the other hand , is a method that uses digital control algorithms to adjust the capacity of a compressor without the need for a VSD . It achieves this by controlling the opening and closing of inlet valves or unloading mechanisms in the compressor . By adjusting these mechanisms ,
SCROLL VS SEMI-HERMETIC
A scroll compressor and a semihermetic compressor are two different types of compressors used in various applications . Here are the pros and cons of each :
Scroll compressor : Pros :
• Energy efficiency : Scroll compressors are known for their high energy efficiency , which can lead to reduced energy consumption and lower operating costs
• Better ability to handle unwanted liquid returning to the compressor
• Lower oil carry-over ( less than 1.5 %) leads to improved system efficiency
• Lower cost compared to other technologies , making this a favourable alternative in a price-sensitive environment
• The design of the Copeland scrolls provides mechanically unloaded starts , which improves efficiency
• Quiet operation : They operate quietly , making them suitable for noisesensitive environments
• Fewer moving parts : Scroll compressors have fewer moving parts compared to other compressor types , resulting in reduced maintenance requirements and improved reliability
• Compact design : They have a compact design , making them suitable for applications with limited space
• High reliability : Scroll compressors are known for their high reliability and long service life
A Sabroe screw compressor . digital unloading can effectively modulate the capacity of the compressor to match the demand for compressed gas , with the use of a solenoid only .
The effect of digital unloading is similar to that of VSDs in terms of energy savings and improved efficiency . By adjusting the capacity of the compressor to match the demand , both methods will reduce energy consumption and minimise wasteful operation . However , digital unloading may have some advantages over VSDs in certain applications . For example , digital unloading can be more cost-effective , is simpler to implement compared to VSDs , is less impacted by load shedding challenges and provides better oil management due to the fact that the system operates at full volume flow .
Cons :
• Limited capacity range : Scroll compressors are generally available in smaller capacity ranges compared to other compressor types
• Non-serviceability : when a compressor fails it is replaced with a new one
Semi-hermetic compressor : Pros :
• Serviceability : Semi-hermetic compressors can be repaired in case of failure , as the casing can be opened without damaging it
• Durability : They offer more durability than open-type compressors as they are sealed against external contaminants
• Copeland semi-hermetic compressors are supplied with ‘ discuss valves ’, which provide optimal compression efficiency
Cons :
• Maintenance : Semi-hermetic compressors require regular maintenance , including oil changes , to ensure optimal performance and longevity
• Larger size : They have a less compact construction compared to scroll compressors , which may limit their suitability for applications with space constraints
• Higher cost compared to scroll compressors
18 www . coldlinkafrica . co . za COLD LINK AFRICA • November 2023