Thermal systems energy optimization employing two independent circuits of double vertical ground U-tube with PCM as the backfill material for building

Abstract

This study presents a numerical transient heat transfer analysis which is carried out on a deep vertical double u-tube ground heat exchanger (GHE) where a specified PCM material is considered as a backfill material for buildings. The stable numerical technique known as Crank-Nicolson method has been employed to solve a series of equations which are derived based on the governing energy balance equations. Transient thermal properties of the GHE such as temperature profile and temperature history of the working material of the GHE including working fluid, the PCM and the soil material outside the borehole is studied in this paper. Furthermore the energy storage history of the borehole thermal heat exchanger system is determined in hourly basis. Finally the energy storage capacity of the GHE is compared when using mortar as a backfill material against the PCM. It is found that using the PCM as a backfill material enhances the performance of the ground heat exchanger as a huge amount of energy is involved within phase change process.