Appliance Design - March 2008 - (Page 41)

INSULATION ductivity (demold) were not compromised. Low Lambda, fast demold The formulation development resulted in the launch of a new PU foam system, System A, which exhibits the requested improved performance of significantly lower Lambda, while maintaining the fast curing properties (and therefore short demold times) and the flow-properties of the reference. The evaluations carried out in the Dow laboratories showed a significant improvement in Lambda value of around 6 percent, compared with the reference Voratec SD 308 polyol. This can be explained by a decrease in the average cell size of the foam. With System A, around 15 percent smaller average cell size is found compared to the reference (See Fig. 1). This corresponds quite well with the theory that follows. It is generally accepted that the thermal conductivity of a foam system can be described by the following general equation: λ = λs + λg + λr where: λs = conductivity of the solid λg = conductivity of the gas λr = heat transferred by radiation The λc, which is the heat transferred by convection, can normally be neglected because of the very fine cell structure of the polyurethane foam and is therefore not included in the equation. The radiation heat transfer contributes for around 15 percent to 20 percent to the final thermal conductivity of a rigid polyurethane foam for the appliance industry relevant density range of 30 kg/m3 to -40 kg/m3. It is directly related to the average cell size, which shows a linear relation based on the following simplified equation as derived by L. D. Booth: λr = 16 Cd (W/m2 ˚ K) where: Cd = average cell diameter As such, small cell size will have a positive impact on the overall thermal conductivity. The observed Lambda improvement by a decrease in average cell size of foams made with System A can be described by the previous equation. curing properties. This system, blown with pure cyclo-pentane, shows good processing characteristics and is giving, on average, a 6 percent improvement in Lambda performance compared with the well-known reference Voratec SD 308 Polyol, while maintaining the good demold characteristics. The insulation efficiency of the cabinet could be improved by more than 3 percent on average, as proven in various models, bringing the performance of hydrocarbon blown foams closer to that of HFC-245fa blown foams. This new technology has been fully validated at industrial scale by BSHG, allowing it to process best-in-class energy efficient foam, using hydrocarbons as a blowing agent, in a conventional single-shot injection foaming process. < For more information, enter . . . . . . . . . . . . . . . . . . . .304 Summary A new hydrocarbon blown foam system has been developed for the domestic appliance industry showing low Lambda and fast For more Information Enter 111 www.applianceDESIGN.com AD03084Foam.indd 1 applianceDESIGN March 2008 41 1/29/08 10:30:52 AM http://www.ecomatesystems.com http://www.ecomatesystems.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - March 2008

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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