Performance Analysis on Heat Transfer Enhancement of Energy Pile with Nanofluid

Abstract

Energy pile is a novel ground heat exchanger with the pipes buried within building piles. The heat transfer performance of energy piles is essential for the ground source heat pump system’s efficiency, economy, and reliability. Nanofluids can improve the convective heat transfer inside the heat exchange pipe and the heat transfer of ground heat exchangers. The improvement of the thermophysical properties of nanofluids has been studied previously. However, only a few research studied the heat transfer performance analysis of a spiral coil energy pile with nanofluids as the heat carrier. Hence, this study will investigate the heat transfer enhancement of the energy pile contributed by a nanofluid. The analytical model of a spiral coil energy pile with seepage and the correlations of thermophysical properties of the nanofluid were employed. The heat transfer capacity, wall temperature, and the outlet temperature of an energy pile under different factors were studied. The results showed that by adopting the nanofluid, the heat transfer of the energy piles increased by 1.21 % ∼ 3.12 %, and the pile wall temperature increased by 0.22 °C–0.47 °C. The increase in the outlet temperature caused by the nanofluid is more significant than that caused by increasing the spiral pitch. It is also is more constant than that caused by increasing the seepage velocity. This work can contribute to improving the heat transfer performance of energy piles.