Appliance Design - November 2007 - (Page 45)

GAS TECHNOLOGY Bosch tankless water heaters have many of the same capabilities. On its modulating units, the company uses ceramic fiber mat burners. Because of the porous structure of the burner, the mixture of gas and airflows through the burner mat and the flame stabilizes on the burner’s surface. When the system activates, the gas valve opens, a fan turns on and draws in a volume of gas and a volume of air and mixes it. “As the flow of water increases or decreases, or the temperature selected is changed, the fan changes its speed and will induce either more or less of the air and gas mixture to the burner,” says Steve Barnard, field engineer for Bosch. Modulation also has the potential to be used in clothes drying appliances where the technology has been proven to reduce drying times in a research project. The NGTC worked with Camco, a Canada-based appliance manufacturer, on a modulating combustion system clothes dryer concept that dries clothes about 30 percent faster. (See Fig. 1.) Modulation was achieved using a two-step gas valve from Italian valve manufacturer SIT. The valve combined with a boosted-capacity burner achieved the reduced drying time. “At the beginning of the drying cycle, when there is a lot of water present, the dryer uses a lot more heat without damaging the clothes,” says Duphily. “As the clothes dry, the heat is reduced so you don’t over heat the clothes. Globally, we use the same amount of energy, more at the beginning and less at the end, but the system can dramatically reduce drying times.” Although the modulating gas dryer never made it into production for marketing reasons, the technical feasibility of the concept was nonetheless established during the research. Residential gas fireplaces represent another application area for modulating gas valves. For example, Sherwood Industries’ Sonnet Fireplace features a 75 percent turn down with automatic modulating gas valve and a programmable remote-control thermostat. The remote control allows the user to remotely adjust the flame height, which requires a modulating system. One of the suppliers that offer technologies to the fireplace industry is Maxitrol of Southfield, Mich. The company is one of the main players in gas modulation systems and their modulating valves can be found in commercial, industrial and residential products around the world. The valves already offer precision control, says Mark Masen, senior engineer, research and development for Maxitrol, but as demands increase, the company felt it needed to increase precision throughout its entire range of modulation. It is currently in lead user testing of a system called Direct-Digital Modulation, or DDM. The unit can be installed on any of the company’s valve products. It is a microprocessor-controlled system that helps regulate valve pressure and make minute percentage changes to the pressure level to help meet the turndown ratios, says Masen. This is important because as turndown ratios reach as high as 20:1, the gas flow rate must be even more precise. Turn down is the ratio of the maximum, or 100 percent, firing rate as compared to the minimum firing rate. If the turn down ratio is 10:1, the minimum is 1/10th of the maximum, explains Masen. To reach these the flow rates, the pressure required to move the fuel becomes more exacting. The pressure amount is a square root of the flow rate, says Masen. “If we say we are Customers everywhere depend on our igniters. No matter where you are, from the North Pole to the South Seas, Saint-Gobain has an igniter to meet your needs. Our igniters deliver dependable performance in gas appliances of every description, from furnaces and boilers to ranges, cooktops, and dryers. Made with a state-of-the-art ceramic, our igniters offer physical and thermal strength, electrical stability, easy handling, and simple installation. They are available in virtually every voltage, including 12V, 24V, 120V, and 240V. 271 CRYSTAR® Igniter 607 Slotless MINI-IGNITER™ For more information about Saint-Gobain Igniter Products(formerly Norton Igniter Products), call us at 603-673-2681 or visit us at www.igniterproducts.saint-gobain.com After all, when it comes to reliability, our igniters beat the others cold. For more Information Enter 117 www.applianceDESIGN.com applianceDESIGN November 2007 45 http://www.igniterproducts.saint-gobain.com http://www.igniterproducts.saint-gobain.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - November 2007

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

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.