| 摘要 |
<p>A pipeline (2) has an inner surface (4) which comes into contact with cryogenic fluid at a temperature of 70K. The outer surface (6) of the pipeline (2) carries a coating of foamed polyurethane having closed cells containing carbon dioxide. The pipeline (2) is located in an outer sleeve (10). The annular space (12) defined between the pipe (2) and the sleeve (10) is filled with perlite powder and is able to be purged with dry nitrogen gas. In operation with the inner surface (4) of the pipelines (2) subjected to a temperature of 70K, the carbon dioxide in the cells of the polyurethane solidifies creating a vacuum therein. This increases the temperature difference across the polyurethane coating and enables the perlite powder to be maintained at a temperature above 77K so that the nitrogen purgant does not condense. A relatively simple alternative to conventional vacuum insulation is thereby provided.</p> |
