Author(s):
1. Esad Tombarević, University of Montenegro, Faculty of Mechanical Engineering, Podgorica, Montenegro
2. Igor Vušanović, University of Montenegro, Faculty of Mechanical Engineering, Podgorica, Montenegro

Abstract:
This paper presents a numerical model for unsteady heat transfer in geothermal borehole heat exchanger. Heat transfer in the fluid circulating in the pipe is considered as one dimensional and governing differential equation is discretized using control volume method. Heat transfer through the pipe wall, grout and surrounding soil is regarded as three dimensional and governing equation is discretized using 3D CVFEM method. Final solution is obtained by simultaneously solving the coupled systems of equations. Numerical solution is verified through comparison with analytical solutions for the cases of simplified geometry or boundary conditions. Overall numerical model is validated through comparison with available experimental results. The abilities of proposed numerical model are demonstrated through analysis of unsteady heat transfer following the step change of inlet fluid temperature where temperature profile of heat transfer fluid along the pipe as well as heat fluxes on the borehole wall and short circuit heat flux are of interest. Finally, the influence of various parameters (velocity and fluid temperature at the inlet, thermal properties of pipe, grout and soil, shank spacing and groundwater flow) are analysed and the results of analysis are systematically presented.

Key words:
3D CVFEM,borehole heat exchanger,heat transfer

Thematic field:
Energetics and Thermal Engineering

Date of abstract submission:
10.03.2017.

Conference:
13th International Conference on Accomplishments in Mechanical and Industrial Engineering