Refrigeration was the focus of the most recent Danfoss EnVisioneering symposium in Baltimore.

consensus to include hydrofluorocarbons (HFCs) in the Montreal Protocol. But with phase down consensus unlikely to be reached in the near future, there could be action in areas in which the U.S. Environmental Protection Agency (EPA) currently has authority, she said. This could include the delisting of HFCs 404 and 507 for use in new commercial systems and retrofits because the global warming potential (GWP) of those refrigerants is considered high.

At the same time, she suggested it is not necessary to start retrofitting systems away from HFCs, especially if the systems are running efficiently. The goal, she said, should be to have a refrigerant management plan.

For new stores, that plan can include using the lowest GWP refrigerant that meets the store’s desired performance needs. For HFCs, she suggested considering the HFC-407 Series of refrigerants or “better still, moving to natural refrigerants.”

For existing stores, Witman urged continuing to retrofit away from hydrochlorofluorocarbon (HCFC)-22, and stockpile that refrigerant to cover your future demands. She then said to consider low-GWP refrigerants and prioritize leak tightness.

Smaller Equipment

The range of refrigerant options for small commercial equipment was explored by Daryl Erbs, director of engineering for The Manitowoc Co. Inc. When looking at HCs, CO₂, ammonia, HFOs, and low GWPs, decisions have to be based on “public image objectives, first costs, energy efficiencies, system design changes, and the regulatory environment,” he said.

Historical research at Manitowoc, he said, involves the use of CO_² in ice equipment including the development of a prototype unit with a two-stage rotary compressor, copper tubing, and an electric expansion valve (EXV) valve. More recent research involves propane and hydrocarbons (HCs) in ice machines and blended ice smoothie refrigeration equipment, he said.

Bigger Systems

Scott Martin, director of sustainable technologies for Hillphoenix Inc., focused on CO_² supermarket refrigeration in North America, referencing the evolution of equipment using distributed technology to reduce HFC charges. He also spoke on systems with secondary glycol, and CO_² with HFCs used in the primary CO_² cascade systems with HFC primary only, to a CO_² booster system that uses no HFCs. In the latter approach, he noted lower gas cooler temperatures. In the configuration is an adiabatic gas cooler to allow for more subcritical operating hours and parallel compression of CO_² flash gas.

Energy Issues

Charles Holcomb, segment manager for Duke Energy, discussed the role of decision makers and energy costs in future innovations. He urged them to look at incentive programs, electronically commutated motors (ECMs), and issues related to coolers, lighting, and HVAC. In all instances, bench marking and measurement is needed. As he noted, “The greenest kWh is the one not used.”

Naturals, Naturally

The move to naturals such as CO₂ and HCs is coming, said Jeff Staub, applications engineering manager for Danfoss. And, it is important to prepare stakeholders for what could be a variety of options. He noted, “There is no single refrigerant that fits all applications and there is no single refrigerant that is best for individual applications.” He said there are stores coming on line with transcritical CO₂ and self-contained systems with propane.

In dealing with natural refrigerants, he urged understanding the refrigerant properties, the need to design for safety, and to design for material compatibility. The process involves gathering information, having controls and components designed for the refrigerant, understanding the application, and designing for efficiency.

Publication date: 12/2/2013

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