# Long-Term Thermo-Hydraulic Numerical Assessment of Thermo-Active Piles--A Case of Tropical Soils
## 3 Results
### Results and Discussions
#### 3.2.3 Influence of Groundwater Flow
With the increase of groundwater flow velocity, the energy exchanged by conduction decreases slightly but increases significantly by advection. In DCV_1, the total amount of energy exchange (sum of \(Q_{in}\) and \(Q_{out}\)) at 0.1 m/day groundwater flow velocity is 68% higher than the 0 m/day  
Figure 13: Thermal and hydraulic results around the pile after 10 years for \(v_{D}\) = 1 m/day: (**a**) Ground-water flow vectors, (**b**) heat flux vectors and temperature profile at cooling peak, and (**c**) heat flux vectors and temperature profile at heating peak. one in the first year, and 585% higher when the water flow velocity is equal to 1 m/day. Due to the relatively large velocity of water flow near the pile, the DCV_1 also has the largest proportion of energy exchanged in advection to the total energy exchanged. Compared to the first year, the energy exchange capacity in terms of conduction decreases in the 10 th year in all control volumes. When water flow velocity is 0 m/day, a 7.8% reduction in DCV_1 and a 3.7% reduction in DCV_5 can be observed. Although a higher water flow reduces the conductive energy exchange capacity more importantly (12.8% reduction for \(v_{D}\) = 1 m/day), the total energy exchange amount increased slightly in some cases, indicating that the groundwater not only maintained the high energy exchange performance of the soil around the pile but even improved it. It is noteworthy that the thermal solicitation of T1 refers to an energy demand dominated by cooling mode. Herein, the thermal balances of the 1 st year and the 10 th year in different control volumes shown in Figure 15 are positive. As the distance from the \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Time**} & \multirow{3}{*}{\(\mathbf{v_{D}}\)} & \multirow{3}{*}{\(\mathbf{Q_{inout}}\)} & \multicolumn{8}{c}{**Energy Exchanged (kWh/m\({}^{3}\))**} \\ \cline{3-13}  & & & & **DCV\_1** & & **DCV\_2** & & **DCV\_3** & & **DCV\_4** & & **DCV\_5** \\ \cline{3-13}  & & & & **Q\_cond** & **Q\_adv** & **Q\_cond** & **Q\_adv** & **Q\_cond** & **Q\_adv** & **Q\_cond** & **Q\_adv** & **Q\_cond** & **Q\_adv** \\ \hline \multirow{3}{*}{Year 1} & \multirow{3}{*}{0} & \(Q_{in}\) & 12.52 & - & 10.11 & - & 8.36 & - & 7.02 & - & 5.96 & - \\  & & \(Q_{out}\) & 7.13 & - & 5.72 & - & 4.72 & - & 3.98 & - & 3.41 & - \\ \cline{2-13}  & \multirow{3}{*}{0.1} & \(Q_{in}\) & 11.05 & 10.53 & 8.57 & 8.11 & 6.89 & 5.87 & 5.69 & 4.09 & 4.82 & 2.81 \\  & & \(Q_{out}\) & 6.74 & 4.64 & 5.22 & 3.66 & 4.20 & 2.77 & 3.49 & 2.07 & 2.98 & 1.57 \\ \cline{2-13}  & \multirow{3}{*}{1} & \(Q_{in}\) & 4.60 & 90.10 & 2.84 & 30.16 & 2.15 & 6.68 & 1.81 & 2.68 & 1.60 & 1.46 \\  & & \(Q_{out}\) & 3.26 & 36.62 & 2.11 & 12.59 & 1.66 & 3.19 & 1.44 & 1.60 & 1.31 & 1.14 \\ \hline \multirow{3}{*}{Year 10} & \multirow{3}{*}{0} & \(Q_{in}\) & 9.06 & - & 7.38 & - & 6.17 & - & 5.24 & - & 4.51 & - \\  & & \(Q_{out}\) & 9.06 & - & 7.38 & - & 6.17 & - & 5.24 & - & 4.51 & - \\ \cline{1-1} \cline{2-13}  & \multirow{3}{*}{0.1} & \(Q_{in}\) & 8.00 & 13.14 & 6.25 & 10.29 & 5.08 & 7.71 & 4.25 & 5.66 & 3.63 & 4.15 \\  & & \(Q_{out}\) & 8.00 & 4.80 & 6.25 & 3.73 & 5.08 & 2.77 & 4.25 & 2.02 & 3.63 & 1.49 \\ \cline{1-1} \cline{2-13}  & \multirow{3}{*}{1} & \(Q_{in}\) & 3.42 & 91.51 & 2.23 & 30.76 & 1.77 & 6.94 & 1.53 & 2.87 & 1.39 & 1.58 \\ \cline{1-1}  & & \(Q_{out}\) & 3.43 & 36.79 & 2.24 & 12.58 & 1.77 & 3.10 & 1.54 & 1.51 & 1.39 & 1.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The energy exchanged in the control volumes for different groundwater flow velocities in year 1 and year 10. Figure 14: (a) Average temperature of the pile-soil interface over 10 years, and (b) fluctuation range of average temperature of pile-soil interface and pile for different groundwater flow velocities. pile-soil interface increases, the thermal balance decreases. It indicates a diminution of the thermal disturbance in the surrounding soil. The thermal balance in DCV_5 is reduced by 98.9% compared to DCV_1 with \(v_{D}\) = 1 m/day in the 10 th year.