Appliance Design - March 2008 - (Page 40)

INSULATION system as benchmark, the energy data confirmed that the gap in favor of HFC-245fa can be significantly reduced using these newly developed HC-blown foam systems, while reducing blowing agent and raw material costs. Even if HFC-245fa remains the leading technology for low Lambda, its very high cost/performance ratio, as well as its unfavorable environmental characteristics, in terms of global warming potential (GWP), reduces the attractiveness of HFC-containing foam systems for the European appliance industry significantly. The outstanding performance offered by these new PU systems, expanded with cyclo-pentane have been fully validated and commercialized at BSHG. They allow bestin- class energy efficient hydrocarbon-blown foam processing while using a single-shot injection technology. Table 1. Influence of Polyol-X on the physical properties of Voratec SD 302. Improved polymer Voratec SD 302 and the Voratec SD 308 from Dow are well-balanced for flow, voids, demold and thermal conductivity. However, in order to address the need of the appliance industry to improve energy efficiency, further optimization of the insulation performance of these systems is required. To enable the improvement of the Lambda values of the foam without compromising on other foam process properties such as demold, or flow, Dow developed a new base polyol for rigid appliance foam-systems called Polyol X. When modifying Voratec SD 302 with Polyol X to understand what this new raw material brings in performance terms, an improvement of the foam properties in the desired direction was obtained, as can be seen in Table 1. An improved Lambda value was achieved. The level of improvement ranged between 2.5 percent to 3 percent. No deterioration in other properties was observed. The curing properties of the system also demonstrated improvement without increasing the average cross-link density of the system. These results have led to further developments with the objective of significantly improving Lambda without deterioration of other foam parameters. The new system design was aimed at maximizing the advantages of using Polyol X in the formulation in terms of thermal insulation properties, and was further fine-tuned so that other critical foam process parameters like flow and prowww.applianceDESIGN.com CFC-11. However, this was known to be only an interim solution while other alternative molecules were investigated, such as chlorine-free hydrofluorocarbons (HFCs), which have zero ozone depletion potential (ODP). After HCFC-141b was discontinued on December 31, 2002, both HFC-134a and HFC-245fa were chosen as blowing agents for polyurethane-foam insulation in refrigerators and freezers. Each blowing agent has its own specific characteristics, resulting in different processes and different final foam performances. Cyclo-pentane is an environmentally acceptable alternative to CFCs, HCFCs, and HFCs. However, it has a higher gas thermal conductivity, as well as higher boiling point than CFC-11, leading to significant performance and cost penalties. Research of other hydrocarbons with a lower boiling point – like alternative pentane and butane isomers – led to the development of PU systems showing better flowability, faster demolding times, and increased cell gas pressure, enabling lower applied densities. However, the insulation property gap versus CFC-11 could not be improved significantly. To meet the increasingly stringent energy efficiency requirements for refrigeration appliances, several options are available for OEMs, each with its own advantages and disadvantages. OEMs have been requesting 40 applianceDESIGN March 2008 their PU raw material suppliers to improve the Lambda values of their foams, but also have been forced to evaluate new cabinet designs, including increasing the wall thickness of the cabinets, and compressor types and sizes. (Lambda values describe a foam’s thermal conductivity, expressed in mW/mK. A lower Lambda means higher insulation properties.) Improving insulation In light of these challenges, Dow Europe GmbH initiated an extensive study to improve the insulation properties of hydrocarbon blown foam systems without compromising on foam process (demolding time) and costs (density). This study was completed within the framework of a joint development program with Bosch und Siemens Hausgeräte GmbH (BSHG), and resulted in the development of new polyurethane systems. These new systems allow refrigerator manufacturers to achieve both energy efficiency and high productivity, reducing costs and specifying the best product solution for any given geographic region. They provide the lowest thermal conductivity and highest energy efficiency using hydrocarbons as a blowing agent in a conventional single shot injection foaming process. When the same cabinet models were injected with a HFC-245fa blown foam 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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