An idea to enhance the thermal performance of HDPE pipes used for ground-source applications

The high-density polyethylene, HDPE, pipes, which are rust-resistant, are used in many ground-source applications that encounter heat transfer processes, in spite of its low thermal conductivity. For applications such as ground heat exchangers, the pipe thermal conductivity plays an important role; where it is required to reject or absorb an amount of heat into or from the ground. In the present study, an idea to enhance the thermal conductivity of this type of pipes is by manufacturing a composite of HDPE/aluminum wires. The wires are circumferentially and equally distributed in the pipe thickness. A computational analysis was carried out to investigate the thermal performance of the proposed composite. The finite volume method was used and a FORTRAN program was developed to model the problem in the polar coordinate system. The results showed a maximum enhancement in the equivalent thermal conductivity of the composite by almost 25% for the 2-mm wires, and 150% for the 3-mm wires depending on the number of wires. As a result, the average outer surface temperature increases in case of the proposed composite that eventually can save pipe's length required to reject the same amount of heat flux.