Estimation of the vertical borehole thermal parameters based on the evolution algorithm using temperature response functions

Abstract

The vertical borehole ground heat exchange performance is still the issue for the engineers installing vertical borehole ground plants using ground-coupled heat pumps. Besides geological and climate change challenges, they face the extraordinary heat transfer process between the circulating fluid and the ground surrounding the U-tube and interactions of vertical boreholes. This paper describes the technique to evaluate the grout, soil thermal parameters and borehole thermal resistance simultaneously using the particle swarm optimization algorithm. The reference thermal response data set from the sandbox laboratory was used for the analysis. A thermal response test (TRT) was made, including the different temperature response functions, for a few time scales. The estimates and errors of the grout, soil thermal conductivity and borehole resistivity were presented and compared with the results of the laboratory experiment and researchers. The target functions, in our case root mean square error values, were less than 0.034 for all analysis cases. The calculation algorithm was written using the Matlab 2016 program and could be easily expanded by increasing the number of target functions and evaluation algorithms. The presented TRT data analysis will increase the knowledge about the vertical borehole ground heat exchange design.

Keywords

• borehole ground heat exchanger
• thermal response test
• G-function
• infinite line source
• infinite cylinder source
• finite line source
• particle swarm optimization.