| 摘要 |
Superinsulation for use in cryogenic tanks comprises hollow insulating spheres of polymeric material which (a) are between 0,32.10<-><2> and 3,81.10<-><2>m in overall diameter; (b) have at least one evacuation hole (22), and (c) are provided with reflective material to form a radiation shield. The reflective material may be in the form of a coating (18) or formed by incorporating reflective material (30) in the structure of the hollow insulating spheres. The outside of the hollow insulating spheres may be coated with a low friction material to facilitate packing. In a superinsulation system comprising first and second walls the overall diameter of the hollow insulating spheres is preferably chosen to be between 1/12 and 1/24 of the distance between the walls. According to the present invention there is provided superinsulation comprising a plurality of hollow insulating spheres composed of polymeric material, characterized in that each of said hollow insulating spheres (a) has an overall diameter from 0.125 to 1.5 inches, (b) has at least one evacuation hole, and (c) is provided with reflective material to form a radiation shield. The reflective material may comprise reflective particles, for example coated microspheres, uncoated glass microspheres, metal chips, silica flakes and mixtures thereof. In the case of microspheres, the hollow insulating spheres are preferably composed of a composite material comprising a polymeric resin and a plurality of microspheres in which the ratio of the volume of the microspheres to the volume of polymeric resin is greater than 1:1. As an alternative to, or in addition to, reflective particles, the hollow insulating spheres may be coated internally or externally with a layer of reflective material which is preferably from 25 to 150 ANGSTROM thick. The coating may be applied direct to the surface of the hollow insulating sphere or over a sealing layer as described hereinafter. In order to facilitate packing (and thereby reducing settlement after initial packing), the hollow insulating spheres are preferably provided with a coating of a low friction material. Preferably the thickness of the wall of said hollow insulating spheres is from 0.005 to 0.09 inches and the overall diameter of said hollow insulating spheres is from 0.125 to 1.5 inches. The present invention also provides a superinsulation system comprising an evacuated insulation space formed between a first wall and a second wall spaced from said first wall, characterized in that the evacuated insulation space contains superinsulation in accordance with the present invention. In such an arrangement the overall diameter of the hollow insulating spheres is preferably from 1/12 to 1/24 of the distance between the first and second walls. |
