issue: April 2007 APPLIANCE Magazine
Refrigeration Systems & Compressor Technology
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by Lisa Bonnema, Senior Editor
Whether improving system efficiency or making the environment healthier, the refrigeration industry is dedicated to designing products that are beyond cool.
Catering to appliance OEMs’ demand for high-efficiency compressors, Embraco of Joinville, Brazil, says its new EGX series achieves a higher EER than other on-off compressors in the market. Its design was based on the company’s EGZ platform and has several improvements, including bearings optimization and an over-molded sealed suction muffler. The compressor is available for household low back pressure (LBP) applications in R134a and 115 V to 127 V 60 Hz, with a capacity range from 600 Btu/h up to 1,050 Btu/h.
Efficiency. A simple word with a simple meaning, yet it has managed to create a whirlwind of activity in every design room of every product manufacturer around the world. And the refrigeration industry is no exception.
The challenge, of course, is designing refrigeration systems that save energy, save costs and, as far as some are concerned, save the world. The good news is that both refrigeration OEMs and their suppliers seem to be up to the task, creating innovative technologies that often meet all three demands.
Commercial refrigeration maker Hill Phoenix (Conyers, Georgia, U.S.) has based an entire series of environment-friendly refrigeration technologies on these demands. The series, called Second Nature®, is currently being tested at two Food Lion grocery stores located in Virginia, U.S. System features include energy savings, less refrigerant and reduced copper piping.
One of the coolant systems, the Second Nature Medium Temperature system, includes refrigerated design cases and walk-in coolers/freezers that the company says have been redesigned to benefit from secondary refrigerant technology. Efficient flooded evaporators are used to provide better heat transfer and faster pull-down after defrost, reportedly resulting in higher quality food products through improved refrigeration shelf life.
Replacing halogenated fluorocarbon R-404A is a non-global warming secondary fluid composed of water and 35-percent inhibited propylene glycol. According to the company, this low-pressure “chilled water” loop eliminates the circulation of high-pressure refrigerant throughout the sales floor and reduces the possibility of refrigerant leaks.
The ability to control product temperatures, not just case temperatures, is said to be another benefit, especially in medium-temperature refrigeration applications such as meat, seafood and produce. The company says temperature is more stable because defrost time is equal to or less than other defrost methods and defrost temperatures are significantly lower. There is also reduced recovery time after defrost, ensuring that the required 41°F (5°C) maximum temperature is achieved.
In addition, because the secondary refrigerant is not under high pressure like the primary refrigerant, the OEM was able to use ABS plastic piping instead of copper piping to construct the refrigeration system. This in itself is said to be more environmentally friendly since the production of copper piping materials uses methods that produce large amounts of greenhouse gases. According to Hill Phoenix, it requires 36 percent more oil to produce copper than is required to produce the engineered ABS pipe. The plastic pipes are also said to have a lower thermal conductivity rate than copper and larger wall thicknesses, making it a better insulator and lowering energy losses.
The air-conditioning industry is also dabbling in new design approaches to create greener products. The Coolerado Cooler from Cooler Air Systems of Arvada, Colorado, U.S., is a new residential series of water-fueled, high-efficiency air-conditioners. As an indirect evaporative cooling system, the air-conditioner relies on the evaporation of water to cool a space without raising humidity. It is said to deliver as much as 6 tons of cooling with an electrical consumption of only 1,200 W.
The “engine” behind the product is the Heat and Mass Exchanger (HMX) from Delphi Corporation. The HMX is based on the thermodynamic cycle known as the Maisotsenko Cycle (M-Cycle), which harnesses atmospheric energy to drive the cooling process.
The unique aspect of the system is that cooling capacity and energy efficiency ratio (EER) of the exchanger increases with the temperature outside, which reduces power consumption during peak demand when utility costs are at their highest. While this means the system is ideal for hot, dry climates, Delphi says the technology behind HMX can be just as beneficial in other applications.
“OEMs have started to realize the Delphi HMX is not necessarily limited by geography or climate, despite being an evaporative approach, and have begun to design systems which capitalize on our unique product features [such as] higher EER with increased outdoor temperature,” says Joseph Dunlop, commercial manager for Delphi Thermal Energy Systems (Troy, Michigan, U.S.). “Major issues such as global warming are also driving the OEMs to look for energy-efficient technologies that are better for the planet and reduce greenhouse gas emissions.”
The heat exchanger has several environmentally friendly features, including the elimination of the compressor and the use of water in place of chemical refrigerants. “In certain applications, systems using the HMX can operate at 1/4 the cost of traditional approaches,” Dunlop tells APPLIANCE.
More traditional refrigeration design approaches are also seeing their share of technology advancements when it comes to increasing efficiency. Danfoss says it has been working on improving both fractional and integral refrigeration system efficiencies. “This has included improved energy efficiency in our reciprocating compressors, scroll compressor products, variable-speed compressors, and more accurate and functional controls, [including] electronic thermostats and electronic expansion valves,” says Frank Pulaski, CRO sales director at Danfoss.
The Baltimore, Maryland, U.S.-based supplier has even designed an aftermarket component that allows homeowners to increase the efficiency of older air-conditioning units and heat pumps without investing in new, higher efficiency equipment. By retrofitting the thermostatic expansion valve, system efficiency can increase by 10 percent to 15 percent on older equipment, depending on the age and capacity of existing system.
Using temperature and pressure sensors to open or close the diaphragm as needed, the valve is said to precisely meter refrigerant flow to maintain proper gas saturation in the coil. An internal check valve, adjustable superheat and adaptable inlet and outlet ports have also been designed to make it easy for contractors to install the valve after selecting the refrigerant, tonnage and connection type. The valve is said to work on most older systems, regardless of the manufacturer.
Bohn, a brand of Heatcraft Refrigeration Products LLC, recently introduced EC motor technology into its Monarch series of air-cooled condensers. According to Subodh Sharma, senior product manager at Heatcraft (Stone Mountain, Georgia, U.S.), the product utilizes an optimized blade and venturi coupled with an integrated variable-speed EC motor to optimize motor speeds to operating loads.
Sharma says the fact that the variable-speed technology is integrated is crucial. “Prior to the introduction of this innovation, the only option to vary motor speeds was through a variable-speed drive system, a complex and costly installation that is prone to motors failures and does not provide the full range of performance one can achieve by using the Bohn Monarch EC condenser,” he tells APPLIANCE. “The system’s ability to match fan speed to load dramatically improves energy efficiency by over 50 percent and reduces the sound level by over 3 dBA, or half the sound level.”
Scott Hix, vice president of product engineering at Virginia, U.S.-based Bristol Compressors, says that although variable-speed technology is certainly not new to the air-conditioning industry, it does represent the biggest opportunity in terms of efficiency improvements and marketing opportunities. This is especially true, he says, when it comes to variable capacity compressors. “As the industry gets better at selling ‘creature comforts,’ in addition to just SEER ratings, modulated capacity systems will become more attractive,” he tells APPLIANCE.
Both reciprocating compressor technology and scroll compressor technology can be used in modulated capacity systems. However, Hix feels that reciprocating designs are more beneficial in SEER-rated air-conditioning applications of 5-ton and below since they have the ability to vary frequency/mass flow over a wide range.
For example, the company’s TS reciprocating compressor is able to modulate between 100-percent and 40-percent capacity. “We do this by reversing the motor for part load and can thereby optimize the motor efficiency for both part load and full load,” Hix explains. “The best selling modulated scroll compressor on the market can modulate only to about 67-percent to 100-percent capacity and does this without reversing the motor so the compressor efficiency is compromised at the full loads condition.”
The Bottom Line
While technology can certainly take the industry to the next level, everyday issues such as production efficiency and cost continue to be at the top of every OEM’s priority list. “As a manufacturer, our biggest current concern is to receive timely shipments so we can meet our production schedules,” says Jack Sinkler, vice president of marketing for Rheem’s Heating and Cooling Division. “Due to the large demand swings that are typical in our industry, we need a supplier to be reliable, even when our demand decreases and increases with weather patterns, legislation, etc.”
Fort Smith, Arkansas, U.S.-based Rheem has explored consignment programs and other methods of vendor managed inventory (VMI) to more efficiently integrate the company’s MRP requirements directly into those of its key suppliers. “This is the type of collaboration that we need to efficiently manage the flow of materials into our manufacturing processes,” Sinkler tells APPLIANCE. “Moving forward, we’ll be seeking additional progress with these types of programs and support tools to continually better manage the flow of our key components.”
Of course, cost is also of utmost concern, especially when it comes to critical system components. “It is important for us to partner with suppliers that can provide us a reliable and competitive product in terms of costs and consistent performance,” Sinkler says. “The cost of the compressor represents such a large percentage of total material costs that it is crucial to ensure our long-term ability to remain competitive.”
Hix of Bristol says cost reduction is a continuous effort and is more often than not the topic of company brainstorming sessions. A recent outcome of those sessions is Bristol’s soon-to-be-released 5-ton R-410 Benchmark reciprocating compressor. The new product uses the same small frame motor as the company’s 3-ton unit. “By doing this, we are able to replace our larger-frame product with a smaller product up through 5 tons, gaining approximately a 32-pound savings in material alone,” he says.
These types of advancements are leading the trend toward tight supplier/OEM partnerships. Sinkler says one of Rheem’s current initiatives is integrating key suppliers into the company’s product development programs as well as directly linking them with production schedules to help assure components arrive at plants when needed. “As key suppliers,” he says, “they must have the ability to respond with new products that meet changing customer and market needs in a timely manner to support business growth.”