Advanced Evacuated Thermal Insulations: The State of the Art

Abstract

Thermal insulation with thermal resistivities of at least 20 (h ft ² F/ Btu in.) have been shown to have the potential for significant energy conservation if employed in residential and commercial refrigerator/freezers Many materials and systems have been proposed which may be incorporated into refrigerator/freezers to achieve this potential.

The current state of the art for advanced evacuated insulations which may achieve resistivities of 20 was established by reviewing data on many materials available in the open literature on the dependence of the thermal performance on internal pressure. The costs for the powdered, fiber, foam and multilayer materials were then obtained from the manufacturer of the products Possible candidate materials for m- clusion into refrigerator/freezers are described and ranked based upon their thermal properties and costs.

Several materials were found that may be used to make super-insulation panels with material costs of less than $1.00 per board foot, if a plastic laminate is used for the container required to maintain the necessary vacuum. Materials falling in this category included. Beverly silica dust, open-cell polyurethane foam, fine perlite, 2.7 lb/ft³ fiberglass and 3.6 lb/ft³ fiberglass opacified with vapor-deposited alu minum, precipitated silica, and mixtures of precipitated silica and fly ash. Mate rial costs approaching $3.00 per board foot will result if metallic contamment is required.