Uniform fractional factorial design tables for energy piles with maximum thermal conductance

Abstract

Energy Piles are the heat exchangers of Ground Source Heat Pumps (GSHP) that transfer the buildings heat to the lower temperature shallow ground reducing the energy consumption in the cooling of buildings. These piles are designed with main objective of lowest thermal resistance. In this paper, nine factors influencing the thermal resistance of the energy pile are defined and statistically evaluated. These nine factors are; number of tubes, pile diameter, tube diameter, tube thickness, tube location, pile conductivity, tube conductivity, soil conductivity, and water flow rate. The thermal resistance of the energy pile is calculated using the line source analytical model. The significance of these factors is evaluated using fractional factorial uniform design tables. The results show significant decrease in the pile thermal resistivity with the increase of the tube diameter, number of tubes, water flow rate, and tube and pile thermal conductivities. On the other hand, decrease of the tube thickness, and pile diameter slightly decrease the pile thermal resistivity. Furthermore, the tubes located near the piles outer surface show significant decrease in the pile thermal resistivity. Also, the soil thermal conductivity has shown insignificant effects on the pile thermal resistivity. 1 2017 WIT Press.