ACR Journal

April | May 2021 ADVERTORIAL 24 Andy Legg highlights recent system refinements that are delivering major improvements in performance for R-32 systems – with benefits for end users and the environment Optimising Chillers and Heat Pumps for use with R-32 Volume 7 No.3 There was an understandable rush to adopt the lower Global Warming Potential (GWP) refrigerant R-32 when it was first proposed as a replacement for higher GWP R-410A in chillers and heat pumps. With a GWP of 675 compared to 2088 for R-410A, R-32 oƒers a major step forward in environmental protection. Early adoption of new technologies, however, can come at a cost, as anyone who invested in a shiny new Betamax video system back in the ‘70s will tell you. There are often unforeseen issues and wrinkles to iron out, and it may take time to fully harness the benefits of new materials and technology. This has proved to be the case with R-32. It is clear that chillers and heat pumps operating on R-32 are not all equal. Some early examples were not fully optimised to operate on the new refrigerant, resulting in lower e’ciency and higher running costs than are now possible with the latest generation of systems. The move to more environmentally conscious options is a priority, and the industry has been highly proactive in responding to the challenge. The risk of prioritising speed to market rather than the performance of the product, however, is that sub-optimal design may exacerbate the problem the solution was intended to address. The majority of a chiller’s carbon footprint results from energy consumption during operation throughout the product lifetime. The greenhouse gas emissions from chiller operation are dependent on the local fuel source, and globally, the majority power plants are run on greenhouse gas emitting fossil fuels. While there are global eƒorts to transition to renewable energy sources aligned with the Paris Agreement, chiller energy e’ciency remains an important factor in addressing climate change. According to the International Energy Agency, without action to address energy e’ciency, energy demand for space cooling will more than triple by 2050 – consuming as much electricity as all of China and India today. The reality is that power consumed accounts for some 80% of a chiller’s carbon emissions. The refrigerant makes up the remaining 20%. In switching to more environmentally acceptable refrigerants, therefore, it is important to ensure that not only is the refrigerant’s GWP as low as possible, and the charge as small as possible, but – critically – that equipment is as energy e’cient as possible. This is the approach that Carrier adopted in optimising the design of its AquaSnap chillers and heat pumps to operate on R-32. It required going back to the drawing board to ensure systems were fully optimised at every stage in the thermodynamic cycle, with careful component selection and testing to ensure the best possible match for the unique properties of the refrigerant The good news is that, due to its operating characteristics, R-32 is up to 10% more e’cient than R-410A. And its carbon- equivalent emission rating is 68% lower. Delivering this theoretical advantage to the greatest possible extent, however, requires careful system design and optimisation. For example, scroll compressors used on Carrier chillers are designed specifically for use with R32. Due to improvements in engineering and design, they operate at maximum e’ciency at minimum and part load conditions, which in many applications is the majority of the time. This results in a significant improvement in overall energy e’ciency and lower operating costs. Further e’ciency improvements are made possible by the use of the latest second generation V-shape Novation micro-channel heat exchangers. Exclusive to Carrier, these all-aluminium components are not only highly e’cient in transferring heat but help reduce refrigerant charge by 40% versus standard copper / aluminium coils. The heat exchangers are paired with the latest high performance 6th generation Flying Bird fans, which have a new multi- blade design for improved aerodynamic performance. Accurate load matching is assisted by the use of variable-speed condenser fans and pumps. Brazed plate heat exchangers with