COMPRESSORS Platforms evolution.
demand. A smaller compressor has a compound of gains, such as reduced production cost, less use of raw materials, better acoustic performance, reduction of the refrigeration charge, and more space inside the cabinet. “But efficiency doesn’t come as a natural result of size reduction. It is by design”, explains Mr Buksar. “When reducing the size, the energy efficiency could, in theory, decrease, but because of the increase in compressor efficiency inside, we can go better than it was before”, says Mr Zgliczynski. They exemplify with the case of customers that started using a compressor of 22 kilograms and now are using one of 8 kilograms, for the same application: “they used an NJ model, with R134a refrigerant, which moved on to R404A, with the NT, then to NEK, and is starting to use now the EMC, with R290 natural refrigerant, working on a same size freezer”, say the engineers.
Natural refrigerants Refrigerant regulations play a very big role in the changes and evolution of compressors throughout time, since the 1980s. “With the Montreal Protocol, in 1987, it was agreed among the participant countries that the world has to protect the ozone layer, and it had a great impact on the compressor industry”, says Mr Sedliak, Nidec Global Appliance R&D Senior Leader - Large Projects, focused on Embraco portfolio. From 1989 on, when the protocol entered in force, the CFCs (Chlorofluorocarbons), used as refrigerant gases until then, have gone through a phasing out schedule. In many cases, they were substituted by HFCs ( hydrofluorocarbons), which, in future studies, proved to be greenhouse gases. So, in 2016, at the 28th Meeting of the Parties to the Montreal Protocol in Kigali, the Parties adopted the Kigali Amendment, in which they agreed to phase down also HFCs under the Montreal Protocol, with a time frame that goes until 2047.
The industry has since then looked for
sustainable solutions. Embraco, now a brand of Nidec Global Appliance, sees natural refrigerants as the way forward, and has been a pioneer in the development of compressors using it, having started studies 25 years ago. Natural refrigerants have very low global warming potential and also contribute to energy efficiency. “The natural refrigerant alone normally gives around 10% to 15% benefit in energy efficiency”, says Mr Buksar.
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Acoustic perception Not only size, efficiency and sustainability have been tackled in this revolution on compressors: improvements in acoustic perception also came along. “Noise is one thing, but acoustic perception is more complex, it involves gas pulsation and vibration, which can affect the overall noise of the unit”, explains Mr Sedliak. “The noise reduction in the refrigerator is really significant and is connected to the fact that the ambient noise in kitchens in Europe has lowered down, because of the use of plastic windows and buildings insulation. So people are more sensitive to noise and they perceive the refrigerator noise as louder”, says the engineer. From Embraco’s first compressor, which was the PW, to now, with de ES, the reduction of noise produced by the compressor has been reduced by 7 dBs.
What made it all that possible How to reduce size, maintain capacity, get more energy efficiency, less noise and, let us not forget, the changes in refrigerant, all in the same product, at the same time? When, in theory, the smaller size would come with less cooling capacity, for example.
“Studying and developing every single part of the compressor ”, say Mr Buksar, Mr Zgliczynski and Mr Sedliak. “Literally every part, because you can think a small bracket is not important, but even a simple bracket is a vibration transmitter, so it is connected to the acoustics,” Mr Buksar adds. “All of that was done through knowledge of physics, engineering, and product design.” “What helped a lot was changes in the mass flow through the compressor due to lower gas superheat. By the change of mass flow, we increase the density of refrigerant inside the cylinder, so even with a smaller cylinder size you get the same cooling capacity”, says Mr Buksar. “The greater difficulty is how to redesign the compressors’ parts, especially valves, to keep it running well, with a more dense refrigerant”, concludes Mr Zgliczynski. While recent technology brought the evolution this far, there is a lot to come in the future. Trends point out to natural refrigerants, variable speed, electronics associated with the compressor and energy integrated systems.
Look out for part 2 - the future, in June’s issue of ACR News.
To illustrate the technology evolution: NE series has evolved from a COP of 1.25 to 1.63
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