Appliance Design - November 2007 - (Page 43)

GAS TECHNOLOGY so that if a baker wants to bake loaf of bread at 450 degrees in a commercial oven, he is actually baking it at 450 degrees,” says Johnson. “Modulation takes the variability of the temperature out of the equation.” By reducing on/off cycles, the units can also help reduce emissions of CO. “Every time a burner ignites, there are puffs of unburned, natural gas and CO released,” says Caroline Duphily, technical manager in the Research & Development office at The Natural Gas Technologies Center (NGTC) in Quebec, Canada, which researches gas technologies. “There is a puff when you ignite the burner and another when it is extinguished. The more cycles that occurs during an operation, the more of these puffs will emit the gases into the atmosphere.” Modulating systems are not without drawbacks, however, and Duphily says that modulation systems should only be considered when an appliance requires varying loads. The disadvantages of modulating systems can be summed up by two words — complexity and cost. Both stem from the need to use specialized equipment such as modulating valves and modulating burners and can often also require more sophisticated controls and sensors, not only to control the combustion process, but also to provide the necessary feedback to determine the required fuel load. This is opposed to the tried-and-true traditional open/closed gas valve that is an “inexpensive, very good piece of equipment,” says Johnson. “Millions are sold and Exploded view of the ebm-papst premix gas blower and venturi. For example, an appliance that can operate at either 70 percent or 100 percent, can often spend most of its time at the 70 percent stage, then kick up to 100 percent when more heat output is needed. Even a simple two-stage design can provide significant energy savings. In one example, a single-stage furnace of 100,000 BTUs that operates at 92 percent efficiency wastes 8 percent of its fuel, or approximately 8,000 BTUs. A two-stage unit will operate the majority of time at 70 percent capacity or 60,000 BTUs and will lose only 5,600 BTUs. Plus, it has the remaining capacity for those few times when the temperature drops below normal and additional heat is needed. Now, imagine if those stages were not just two, but many. That is variable modulation — being able to more precisely regulate the amount of fuel supplied to closely meet the energy needs of the appliance. In addition to energy efficiency, the modulating systems allow for precise control of temperatures. This control offers myriad benefits such as improving food quality in cooking applications and enhancing personal comfort in heating applications. When modulation is used in an oven, bakers can make a confection at a certain temperature knowing that the temperature is within a degree or two of the temperature for which it was set. When used in water heaters or furnaces, the same is also true — the system hits a specific temperature target and holds it consistently. In research by Frank Johnson of the Gas Technology Institute (GTI), a Des Plaines, Ill.based technology center, the temperature of a modulated oven was kept to within 5 DegF of the set point, as opposed to a traditional system that had swings of as high as 50 DegF. “A modulating system gives a nice even heat www.applianceDESIGN.com For more Information Enter 116 applianceDESIGN November 2007 43 http://www.isphording.de http://www.isphording.de http://www.appliancedesign.com

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Appliance Design - November 2007 Contents Editorial Shipments/Forecasts News Watch Today’s LEDs are Brighter and More Colorful than Previous Versions, Allowing Designers More Opportunities to Improve and Differentiate Their Products. When Converting from CCFL to LED Backlights in LCD Panels, New Driving Methods are Needed. Electrowetting Technology Allows Displays to be Designed in an Extensive Range of Colors. Noise Problems are Not Always Easy to Find or Fix, but Acoustic Labs Can Help Designers Ferret Out the “Good” Noise from the “Bad.” A New Sanitization Protocol for Clothes Washers Combines the Best of Three Well-Established Provisions to Ensure Efficiency, Quality and Safety. Stricter EMC Requirements Raise the Bar for Appliances with Electronic Controls and Require Testing to New Levels. Despite Added Cost and Complexity, Gas-Modulating Systems have Migrated from Large-Scale Boiler Applications to Smaller Residential and Commercial Furnaces and Appliances. A New Treatment Technology Hardens the Surface of Light Alloys such as Aluminum and Magnesium and Expands Their Potential Applications. DesignMart Advertiser’s Index Association Report: AHAM

Appliance Design - November 2007

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