Appliance Design - March 2008 - (Page 38)

INSULATION Optimizing Objectives Fig. 1. The magnified image at left shows the foam cell size of System-A foam taken from a refrigerator. Image at right shows the cell size of Voratec SD 308 foam taken from a refrigerator. New polyurethane system delivers improved efficiency and high productivity. by Sandro Kohn, Hans Kramer, Vanni Parenti, and Dasaradh Kumar Patchala Sandro Kohn is team manager, hygiene and insulation; and Dasaradh Kumar Patchala is development engineer, plastics and insulation; at Bosch un Siemens Hausgerate, GmbH, Giengen, Germany.Vanni Parenti is global industry leader for domestic appliances, Dow Italy S.r.l., Correggio, Italy; and Hans Kramer is senior application development specialist for rigid polyurethane foams, Dow Europe GmbH, Freienbach, Switzerland. 38 applianceDESIGN March 2008 hen evaluating polyurethane (PU) systems for household appliance applications, short demold times have typically forced PU processors to choose between strong insulation performance and higher productivity levels. Now, driven by the twin global needs for improved energy efficiency and high performance, the Dow Chemical Co. has developed new foam systems using various blowing agents – with a strong focus on hydrocarbons (HCs) – that allow refrigerator manufacturers to achieve both enhanced insulation performance and high productivity. These new systems also address the specific technical issues of the refrigeration industry in different regions around the world. W The greening of appliances The Montreal protocol of 1987 required that chlorofluorocarbons (CFCs) be replaced in order to preserve the stratospheric ozone layer. As a result, the global appliance industry has been striving to eliminate CFC-11 and select alternative blowing agents. In the early 1990s, the European appli- ance industry moved away from halogenated blowing agents for the expansion of rigid polyurethane foams used to insulate refrigerators and freezers and turned to hydrocarbon blowing agents. The use of hydrocarbons as a blowing agent for appliance insulation has rapidly expanded in other areas of the globe as well, making hydrocarbons the blowing agent of choice in Europe, the Pacific and Latin America. Over time, the global appliance industry has learned how to process hydrocarbon blown foams and what to expect in terms of foam performance and properties. Initially, cyclo-pentane was chosen due to its lower thermal conductivity, compared with other hydrocarbons molecules. However, further optimization has led to the introduction of other pentane isomers as sole blowing agents, as well as a co-blower of cyclopentane. This was done to reduce the cost penalties of increased applied densities and process disadvantages, such as poorer flow and longer demolding times. In the U.S., the primary approach focused on HCFC-141b as a first alternative for www.applianceDESIGN.com http://www.appliancedesign.com

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Appliance Design - March 2008 Contents Editorial Shipments/Forecasts News Watch A New Appliance is Set to Break into Homes Soon - the Micro CHP Unit, which Generate both Heat and Power. Thermally Enhanced Varistors Help Protect Low-Power Systems Against Damage Caused by Over-Current, Over-Temperature and Over-Voltage Faults. Hybrid Controller Reduces Standby Power Consumption and Improves Active-Mode Efficiency. Battery-Management ICs Solve Design Challenges for Cordless Appliances Using High-Voltage, Lithium-Ion Battery Technology. A Semiconductor Solution Protects the Relay in a Temperature Controller for a Cooking Appliance. New Polyurethane Foam Insulation System Optimizes both Insulation Performance and Productivity. Innovations in Decorative, Pre-Finished Metals Expand Range of Design Options for Appliance Designers. Design Marts Association Report: AHAM Advertiser's Index

Appliance Design - March 2008

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