Passive Refrigeration for Arctic Pile Supports

Abstract

This paper demonstrates the feasibility of passive refrigeration for maintaining soil stability near pile supports in permafrost. Laboratory tests for Alyeska pipeline pile supports have evaluated the heat removal capabilities and operational limitations of two passive refrigeration schemes—the air convection pile, a single-phase open system driven by natural convection of cold air, and the heat pipe, a closed system natural convection, two-phase, heat transfer loop which depends on an internal vaporization and condensation cycle. The laboratory tests show that heat removal rates are high enough from either refrigeration scheme to effectively “freeze-in” pile supports and thereby substantially increase their load-carrying capacity in many permafrost regions. While the paper concentrates on laboratory results, reference is made to field tests and computer calculations which confirm laboratory predictions and suggest their usefulness as design data for other Arctic applications of passive refrigeration schemes. The use of heat pipes in piles supporting elevated portions of the Trans-Alaska Pipeline is one example of successful application of passive refrigeration. Other potential applications include protection of permafrost near Arctic construction sites and near oil producing and processing operations.