As refrigerant regulations continue to progress rapidly, commercial refrigeration stakeholders are looking for refrigeration solutions capable of balancing their sustainability, serviceability and equipment lifecycle goals. Emerson recently completed the development of a new distributed system architecture called Copeland scroll booster. It is designed specifically to help food retailers achieve these goals while providing the flexibility to accommodate a wide range of low- (LT) and medium-temperature (MT) applications.
When searching for viable and sustainable commercial refrigeration strategies, stakeholders often find themselves weighing the pros and cons of many different system types. Systems that use alternative refrigerants with a global warming potential (GWP) below 150 typically introduce increased service complexities and lifecycle costs. Other systems may not quite achieve sustainability targets but offer serviceability improvements. And when you consider the ever-expanding diversity of system designs needed to address modern commercial refrigeration requirements, system selection becomes even more complex.
Much of the work taking place at Emerson’s The Helix Innovation Center is focused on solving this industry-wide challenge, and the Copeland scroll booster architecture is a key outcome of these efforts.
Leveraging a new refrigerant alternative
Regulatory mandates are driving significant changes within commercial refrigeration system designs to minimize environmental impacts. Many operators are seeking alternatives to traditional centralized direct expansion (DX) refrigeration systems, which utilize large charges of high-GWP hydrofluorocarbon (HFC) refrigerants and are prone to leaks. This has led to an increasing variety of distributed refrigeration approaches — which offer smaller refrigerant charges, lower-GWP refrigerants and wider application flexibility.
Although natural refrigerants CO2 (R-744) and propane (R-290) have the lowest possible GWP ratings, they also come with high operating pressure (R-744) and flammability (R-290), introducing operational complexities and design limitations that many food retailers may not be prepared to address. Newer refrigerant blends — such as the A1 hydrofluoroolefin (HFO) refrigerant R-513A — deliver excellent performance characteristics, much lower GWP than HFCs and zero flammability. Offering the lowest possible GWP (573) among non-flammable refrigerants, R-513A has low-pressure characteristics that provide a familiar operating envelope and require no special training, certification or safety mitigation measures.
Mechanics of Copeland scroll booster
The Copeland scroll booster system is designed to use R-513A for both LT and MT refrigeration loads. Its distributed architecture offers an efficient and environmentally friendly alternative to large centralized systems. System configurations can scale from small, low-charge condensing units to larger distributed racks charged with several hundred pounds of refrigerant.
This innovative technology overcomes the typical challenges of operating a low-temperature system, including requiring compressor cooling via liquid injection and lowering compressor lifespan due to high compression ratios and discharge temperatures. This straightforward architecture leverages the advantages of R-513A’s low-pressure, high-efficiency and key system components to significantly lower discharge temperatures and compression ratios.
This flexible architecture is comprised of one or more MT scroll compressors coupled with one or more LT scroll compressors, where MT compressors can either be placed in a condensing unit or within a typical rack configuration. Condensers may be located remotely or integrated into the system and placed indoors or outdoors. To help reduce refrigerant charge, piping and associated costs, the LT scroll compressors can be placed near the LT evaporators, i.e., directly on top of or beside the case or remotely near the load.
The “booster” design strategy provides significant performance improvements by discharging (or boosting) the LT compressor directly into the nearest MT compressor’s suction line. The lower discharge temperatures of the LT scroll compressor minimize the suction gas temperature of the MT unit and allow the MT compressors to operate within their design limits without the need for additional cooling. The net result is an overall system efficiency gain while greatly minimizing the mechanical loads on the LT compressors.
Simplifying operational complexities
The innovative use of a low-pressure, low-GWP refrigerant within a simple, distributed architecture that’s based on familiar operating principles fills an urgent need within the larger food retail market. The Copeland scroll booster system helps operators to meet their sustainability goals without introducing unnecessary serviceability complexities. Offering the design flexibility to service store formats of varying sizes, its benefits check many key boxes on the list of modern supermarket refrigeration priorities:
- Lower-GWP, A1 refrigerant (i.e., R-513A)
- Reduced refrigerant charge
- Lower leak rates due to lower-pressure system
- Lower utility costs
- System familiarity with technicians and end users
- Low total cost of ownership (TCO) from lower annual energy consumption and lifecycle climate performance (LCCP)
- Secure remote facility monitoring capabilities
Proof of concept and future evolution
Emerson has conducted successful trials of this technology in various applications and climates. This year, a distributed scroll booster system was installed at Gem City Market, a new small-format supermarket built in Dayton, Ohio. The project involved collaboration among the surrounding Dayton community, city officials and commercial refrigeration industry leaders — including Hussmann and Chemours — who donated their respective expertise and resources to the project. In the future, when even lower-GWP refrigerants (such as A2Ls) are approved for use by applicable codes and standards, a distributed scroll booster system can be adapted for use with these ultra-low refrigerant alternatives (less than 150 GWP).
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