24 August 2021
Nicol Low, chief operating officer at Vert Technologies, looks into the different factors refrigeration OEMs should consider when developing new solutions.
The compressor is an integral part of refrigeration equipment. Yet, despite the increased focus on the environmental credentials of the sector, innovation has not necessarily moved on at a similar pace. However, time does not stand still, and new solutions are needed to tackle the important issue of sustainability if the technology is to be fit for the future.
Insofar as compressors are concerned, the refrigeration sector has seen little innovation in the last 40 years. To an extent, this is understandable – as the old phrase goes, if it isn’t broke, don’t fix it. After all, a primary, prioritising concern for refrigeration OEMs has always been ensuring their products are compatible with varying loads and temperatures and can operate at high pressures. If a solution fits this remit, this has traditionally been sufficient.
As such, the current technology employed for compressors has usually been seen as the best choice for those in the industry. Used to control the circulation of the refrigerant throughout the equipment’s system while drawing vapour away from the evaporator at lower pressures and temperature for condensing, these are often picked solely for function.
F-Gas and long-term sustainability
The mounting legislative pressure on refrigeration OEMs to make equipment greener is significant and will only increase. Beginning with 1987’s Montreal Protocol, which outlawed chlorofluorocarbons (CFCs) and continuing with the 2016’s Kigali Amendment to gradually curb hydrofluorocarbon (HFC) use, the sector has been subject to gradually tightening environmental legislation. This has culminated in the F-Gas ban, which came into force in the UK and EU in January 2020 and banned any HFCs with a global warming potential of 2500 or over.
The ban specifically applies to all refrigeration systems containing HFCs equivalent to over 40 tonnes of carbon dioxide. With this in mind, upheaval and innovation are patently required to adhere to this rapidly shifting legal landscape. This involves phasing out refrigerants with a high global warming potential (GWP), including R410A and R134A, alongside R404A. However, this is easier said than done. Though low-GWP refrigerants exist in ammonia and carbon dioxide, they require high-pressure ratios and extremely high absolute pressure for effective compression.
Additional innovation required
As innovation in the compressor space has stood relatively still for an extended period of time, there are still unanswered questions around whether current technologies can work with low-GWP refrigerants of the future. Indeed, traditional units may need to be daisy-chained to reach the parameters required to compress them, resulting in additional CapEx spend and further OpEx expenditure to keep additional units running. This is less than ideal and places additional pressure on the package size of the final product – a potential issue in a domestic setting.
More research and development is required to build units that can effectively use low-GWP refrigerants without compromising on the final product experience for consumers. It could be said that the sector needs to consider a whole new approach to compression.
By bringing innovative thinking to the table, companies prepare themselves for the long-term shift towards more stringent environmental legislation. At Vert Technologies, for example, we are working on projects with a number of refrigeration companies looking to bring new thinking to their products, using low-GWP refrigerants in conjunction with our conical rotary compressor (CRC) solution.
Rotors and rotor software
A key aspect of the design approach is working hand-in-hand with OEMs, as this enables existing technologies to be further developed and capabilities increased. So, though we believe the benefits of the CRC are clear – high pressure in a single stage, high absolute pressures and low noise – combining this collaborative strategy with in-house expertise has generated considerable leaps in terms of pressure, efficiency and flow capabilities for the CRC, with efficiency savings of more than 30% in air compressor mode over the last two years.
The design process of the rotors and its accompanying software have also benefitted from a collaborative approach with OEM partners. There are two aspects to the CRC that makes it unique. Firstly, the design, which uses one rotor placed inside another, with each turning in the same direction to compress refrigerants as it moves down the conical screw, enabling high pressures, low noise, and low vibration. The second is that software can optimise the CRC’s rotor geometry, suiting the high pressures required by different mediums and applications, such as refrigerants.
To develop innovative solutions that suit customer applications, designers must look at four different design outputs – required flow, inlet and outlet pressures and system power – while remaining in step with the OEM’s specific requirements. In our design process, we generate rotor surfaces in 3D for performance analysis in software before passing design data to the engineering department to create the rest of the compressor hardware.
Parts are then measured using in-house metrology and CMM before being passed to the assembly team for building and commissioning. Having all the necessary design, manufacturing, metrology, assembly and testing in-house means Vert can develop hardware solutions to customer enquiries quickly and efficiently.
Material selection and scaling up
The materials used in compressor solutions also represent another opportunity for innovation, with its selection based upon multiple factors, including what the target market is, how price-sensitive the sector is, and what the ultimate performance of the product is to be. Therefore, compressor designers should be able to adapt to various markets and products to ensure that the best material is selected for use. These can include engineering polymers, invar, stainless steel, brasses and aluminium – again, this is all based on customer requirements, and designers need to be aware of these variations when developing new solutions.
Of course, a key concern for any new compressor solution is whether it can be scaled up to the large volumes needed. Consequently, designers and OEMs should have a continuous eye on production and manufacturing, ensuring this expansion can be executed as cost-effectively and simply as possible for the OEM. This can be seen at Vert, where we investigate manufacturing strategies to enable this, including moulding, forming and forging/casting. We are also exploring options around grinding and tight tolerance final machining at large volumes for high-use and HVAC systems.
In conclusion, the refrigeration sector cannot stand still in its efforts around innovation, and nowhere is this more apparent than in compressor technology. Indeed, there are numerous challenges involved for designers looking to develop more efficient and more sustainable refrigeration equipment for OEMs. However, by adopting an end-to-end approach and working closely with the customer, progress can be made toward realising solutions that can meet the future’s challenges, including tightening sustainability legislation.