The vertical borehole heat exchangers were surrounded by the heterogeneous multilayered geological environment
and groundwater flow that affected the performance of borehole plants. In this paper, the field investigation of vertical
borehole ground heat exchangers in capital city Vilnius (Visoriai), Lithuania is presented. The numerical heat transfer
model considering seven different geological strata was developed using the cylindrical heat sink model for vertical
borehole inside by solving the soil mass and heat transfer equations with groundwater flow. The numerical multilayered
ground vertical borehole heat transfer model was calculated and validated by in-situ thermal response test data. The numerical
model results were also compared with the homogeneous finite difference model expressed by the temperature
response functions (well known as “g-functions”). The practical realization of g-functions was designed in the Earth
Energy Designer as a practical tool for geoengineers designing the vertical borehole plants. The temperature profiles at
borehole wall at different heating times were presented and explored together with relative errors. The numerical model
will be used as a practical tool for the Lithuanian Geological Survey under the Ministry of Environment to estimate the
underground conditions for the consumption of shallow geothermal energy.
Numerical modelling of vertical borehole heat exchangers performance under Lithuanian
Quaternary conditions
