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issue: April 2009 APPLIANCE Magazine

Refrigeration Systems & Compressor Technology
Expanded Online: Engineered to Conserve

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by Lisa Bonnema, Contributing Editor

 Refrigeration system suppliers continue to focus their efforts on conservation.

Although the refrigeration industry has been working to be “greener” for years, higher energy prices added even more fuel to the fire for conservation. But with oil prices coming back down it would seem relevant to question whether conservation efforts—and interest—might subside.

One supplier's research shows that those in the supermarket industry, at least, remain on the conservation bandwagon. Midland, MI, U.S-based The Dow Chemical Company (www.dow.com), which manufactures the heat transfer fluids used as coolants in secondary-loop refrigeration systems, interviewed a group of in-store engineers, consulting engineers, and installers who work with grocery store refrigeration systems to find out whether or not the trend to "go green" would decline along with energy prices. The good news: 92% of their respondents stated that energy conservation was very important in the design, installation, and operation of the refrigeration systems with which they worked. Dow also found that eco-friendly secondary-loop systems, which are designed to use less refrigerant, continue to be an appealing option for end users. Almost 30% of respondents said they already use secondary loop systems, and another 32% said they are planning to install one, despite the state of the economy.

“I don’t believe we can afford to slow down the investment in energy-efficient equipment,” says Travis Lumpkin, vice president of Systems Business Development at Kysor//Warren
(Columbus, GA, U.S.; www.kysorwarren.com). “Not only will investments like this impact our natural resources, but they will continue to improve the operating costs of customers who invest in energy-efficient equipment. Bottom line, I believe the consumers do and will continue to demand the use of more-energy-efficient equipment.”

Of course, much of the time new standards give industry little choice. The most recent legislation to affect U.S. refrigeration is a federal efficiency law for walk-in coolers and freezers manufactured after January 1, 2009. The law includes a number of prescriptive measures to improve the efficiency of walk-in coolers and freezers with a total chilled storage area of less than 3000 sq ft. Those working to comply are tweaking everything from doors and insulation to motors and lighting to make energy-saving improvements. Under the new law, units installed after January 2009 have to use either electronically commutated (EC) or three-phase motors for evaporator fan motors under 1 hp and less than 460 V. For the average grocery store cooler, this means upgrading the 30 to 40 shaded-pole and PSC induction motors to run evaporator fans.

To help equipment makers transition to EC technology, Wellington Drive Technologies Ltd. (Buffalo Grove, IL, U.S.; www.wdtl.com) designed its new ECR 85 and 95 motors to match the exterior design and airflow of shaded-pole and PSC induction motors traditionally used in walk-in coolers, but with efficiency ratings over 70%. “For engineers designing coolers, the challenge is to find the technology or combination of technologies that save enough energy to meet legislation, at the lower cost and as close to ‘drop-in’ replacements of what they were previously using as possible,” notes Jamie Wilkinson, chief engineer at Wellington.

Efficiency gains stem from the fact that the new ECR motors run “cool.” Wilkinson explains: “Walk-in cooler motors have traditionally been shaded-pole motors, which have very high losses, meaning that about 75% of the energy used by the motors is released as heat in the walk-in cooler. PSC induction motors have better efficiency, but much lower than the 70% ratings of the ECR 85/95.”

U.S. walk-in cooler and freezer OEMs are using EC motors like the ECR85/95 from Wellington Drive Technologies to meet the latest federal regulations. Through the use of engineering plastics and a proprietary design, Wellington's motors are said to offer the same exterior design and accessories as traditional shaded-pole and PSC induction motors, but with efficiency ratings of more than 70%.


Efficiency Steps

Like Wellington, refrigeration system suppliers across the board are designing new products to help equipment makers comply with regulations—and gain some efficiency edge. Embraco (Joinville, Brazil; www.embraco.com) developed a new variable-capacity compressor (VCC) exclusively for the European market to help manufacturers meet the region’s 2010 energy regulations. The VEMX, launched in January, is said to surpass the energy efficiency level of its predecessor by 5% and overcomes the technological challenges of conventional VCC compressors.

According to Ernani Nunes, Embraco Cooling Solutions manager, the increase in efficiency was possible due to the optimization of the valve system and the lubrication system of the compressor. “The operating principle of most hermetic compressor oil pumps is based on centrifugal force, whose efficiency drops drastically with a decrease in the rotational speed of the motor,” Nunes says.

Working with the Federal University of Santa Catarina, in southern Brazil, Embraco was able to design a compressor with a larger range of operating speeds. “Through simulations and mathematical modeling of the phenomena involved in the flow of the oil inside the compressor, we arrived at a design that reduced the lower limit of the compressor’s operation by 25%,” Nunes says.

With a lower rotational speed, Nunes says engineers are able to reduce even further the number of on-off cycles of the compressor since it can deliver the exact refrigerant mass flow that the system needs to maintain the internal temperatures. “A compressor that operates at low speeds will have, as a result, very low energy consumption and very low noise levels,” he notes. “In other words, we were able to better regulate the cooling capacity; therefore, the system can stay on longer, but with reduced consumption.”

The Apexx VSH compressor was named Product of the Year at this year’s AHR Expo. Developed in Denmark by Danfoss (www.danfoss.us), it was noted as an innovative high-capacity variable-speed scroll solution for commercial R-410A air-conditioning and heat pumps. The unit combines a high-efficiency scroll compressor with a variable-frequency drive. “The compressor drive is designed to protect the compressors via advanced current monitoring, short cycling protections, increased robustness toward voltage imbalances, and high discharge temperature protections,” explains Mogens Rasmussen, business development manager, Apexx VSH project. “The oil management is also controlled via the drive and, because of the drive’s inherent soft start, inrush current is eliminated. These safety features add to increased reliability.”

With the new compressor, the load demand and compressor capacity are continuously matched and, therefore, the coefficient of performance (COP) is higher. “Speed is controlled by the frequency output of its drive—from 30 to 90 Hz,” Rasmussen explains. “The VSH also has inherent efficiency advantages with continuous operation. It does not have the same cycle losses as in fixed-speed units, where on-off cycling generates higher amps at start-up and thermal losses.”

Forward movements like these help encourage and empower equipment designers, even if the road ahead is a long one. “The global trend of minimizing greenhouse gas (GHG) emissions will continue to drive compressor development toward higher energy efficiency, especially wider use of variable-speed drives,” Jurgen Suess, vice president, research and development, Danfoss A/S, tells APPLIANCE. “The displacing principles of compressors—both positive displacement and centrifugal—are well understood, and their advantages and drawbacks are well known. Don’t expect new concepts to be introduced. This evolution of compressors will continue well into the next decade and beyond.”

On the Horizon

The refrigeration industry remains aware of the looming phaseout of HCFC-22. And while the transition is inevitable, it won’t be easy—or cheap. “Some HFC refrigerants, such as R-410A, operate at significantly higher pressures, and manufacturers will need to design equipment that accommodates this new operating characteristic,” notes Craig Thomas, business manager of Fluourchemicals-Refrigerants, North America at fluorocarbon producer Arkema Inc. (Philadelphia, PA, U.S.; www.forane-us.com). “Also, HFC refrigerants require the use of POE oil to ensure proper lubrication and oil return. POE oils are not as easy to use as the mineral and alkyl benzene oils used with R-22.”

Suppliers like Arkema are trying to ease the pain by offering reclaim programs and investing heavily in HFC components such as R-32 and R-125, the basis for R-22 replacements like R-410 and R-427A.

Lumpkin of Kysor//Warren feels that CO2 is the future of refrigeration systems. “We are investing in the development of systems that use natural refrigerants, specifically carbon dioxide,” he says. “This new refrigeration system reduces the dependency on large quantities of HFCs, reduces the impact on the environment if leaked into the atmosphere, and reduces operating expenses.”

Still, equipment makers have to convince their customers that going green can actually mean more green in their pockets. “There are technologies available today that can reduce energy consumption, improve system performance, and reduce a store’s overall carbon footprint,” Lumpkin says. “It’s our responsibility to ensure that the resources we have available to us today are still available for generations to come.”

The Danfoss Apexx VSH combines a high-efficiency scroll compressor with a variable-frequency drive. The drive’s frequency output, from 30 to 90 Hz, controls the capacity delivered by the compressor, and enables the system to always deliver the capacity that meets load demand.

Embraco engineered the VEMX variable-capacity compressor to help European refrigerator OEMs meet 2010 energy regulations. The unit is more efficient than its predecessor and uses isobutene (R600a) as a refrigerant.


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