The US Household Refrigeration Industry is, once again, facing a double regulatory challenge. Effective July 1, 2001 the household refrigerators and freezers sold in the USA must be significantly more efficient than those sold today. Eighteen months later the use of HCFC 141b for foam blowing is prohibited in the USA. The blowing agents that are currently acceptable to the US EPA as candidates to replace HCFC 141b have higher vapor phase thermal conductivity. This leads to higher heat flow rates through the polyurethane foam insulation. Higher heat flow generally means a less energy efficient refrigerator or freezer. Over the last two decades, more features have been incorporated into refrigerator and freezer designs. This has resulted in more items being "hidden" in the insulation space between the outer case and inner liner. These "hidden" items are often shaped or placed in such a manner that filling the cabinet with foam is impeded. In the past, this has been more a manufacturing inconvenience than a hindrance to energy consumption performance. In the future, impeding foam flow can mean the difference between meeting the energy standards or not. By understanding the process of foam insulating household refrigerators and freezers the designer can help maximize insulation performance.
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