Abstract
A novel paraffin/graphite phase change material was proposed as backfills for prestressed high-performance concrete piles. An experimental device for high-performance concrete energy pile was established to access the thermal performance of paraffin/graphite phase change material backfill and a finite element method numerical simulation based on the experiment was conducted. Two theoretical models, Multiphase-Effective Medium Theory and Maxwell-Eucken with parallel, were proposed to calculate the thermophysical parameters of paraffin/graphite phase change material. The results show that Multiphase-Effective Medium Theory achieves enhanced reliability than Maxwell-Eucken with parallel in the thermophysical parameters calculation of multi-phase composites. Paraffin/graphite phase change material can enhance the heat storage capacity of paraffin/graphite phase change material and reduce the temperature fluctuation of the piles, while graphite can accelerate the heat transfer within the pile system. A “transition point” in dynamic competition between the graphite and paraffin of paraffin/graphite phase change material was first discovered during the heat transfer process, which can be employed as an indicator for the operational patterns of the prestressed high-performance concrete energy pile. The thermal performance of prestressed high-performance concrete energy piles can be improved by reasonably controlling the graphite and paraffin contents in paraffin/graphite phase change material backfills.
Published Version
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