Finite-element analysis of the fluid temperature distribution in double U-tube Borehole Heat Exchangers

7th European Thermal-Sciences Conference

Zanchini, E.^1 ; Jahanbin, A.^1

University of Bologna, Department of Industrial Engineering, Viale Risorgimento 2, Bologna

40136, Italy^1

关键词: 3D finite-element simulation;    Approximate analytical methods;    Arithmetic mean;    Borehole heat exchangers;    Mean temperature;    Outlet temperature;    Renewable energies;    Thermal response test;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/745/3/032002/pdf
DOI  :  10.1088/1742-6596/745/3/032002

来源: IOP

【 摘 要 】

In the evaluation of Thermal Response Tests (TRTs) and in the design of Borehole Heat Exchanger (BHE) fields, the mean temperature of the fluid Tmis usually approximated by the arithmetic mean Taveof inlet and outlet temperatures. This approximation can yield errors in the estimation of the thermal conductivity of the ground, of the BHE thermal resistance, and of the heat pump performance. An expression for the evaluation of Tmhas been proposed by Marcotte and Pasquier (Marcotte D, Pasquier P 2008, Renewable Energy, 33 2407) for single U-tube BHEs. In this paper, the difference between Tmand Taveis determined by 3D finite- element simulations for a typical double U-tube BHE in 6 unsteady working conditions. The results are validated qualitatively through an approximate analytical method, and show that the expression proposed by Marcotte and Pasquier underestimates the difference between Tmand Tavewhen applied to a typical double U-tube BHE. Therefore, new relations to evaluate this difference for double U-tube BHEs would be useful.