## 6 Results and Discussions
### The Lambeth College Case
The fitting value is 6 Wm\({}^{-2}\)K\({}^{-1}\) for VWSG 4 and 5 Wm\({}^{-2}\)K\({}^{-1}\) for VWSG5. 2. For VWSG 1, 2, and 3, the approximate \(h\) values are different in the cooling and heating mode circles. In the cooling mode period, the approximate \(h\) value for both VWSG2 and 3 is 3-4 Wm\({}^{-2}\)K\({}^{-1}\), while this value in the heating mode circle is 5 Wm\({}^{-2}\)K\({}^{-1}\) for VWSG2 and 3 Wm\({}^{-2}\)K\({}^{-1}\) for VWSG3. For VWSG1 the curves match when \(h\) = 5-6 Wm\({}^{-2}\)K\({}^{-1}\) in the cooling mode and over 6 Wm\({}^{-2}\)K\({}^{-1}\) in the heating mode. For the five groups of VWSGs, the hot/cold heat transfer coefficients are summarized in Table 3. For VWSG1 and 2, the heat transfer coefficient in the heating mode is larger than that of the cooling mode. For VWSG3 the result is the opposite, and the curves match with a higher \(h\) value in the cooling mode. For VWSG4 and 5 a single consistent heat transfer coefficient value works for both heating and cooling modes. The result of Table 4 can partly support the assumption made in previous sections. \begin{table}
\begin{tabular}{l c c c c c} \hline  & **VWSG1** & **VWSG2** & **VWSG3** & **VWSG4** & **VWSG5** \\ \hline \(h_{\text{hot}}\) vs. \(h_{\text{cold}}\) & \(>\) & \(>\) & \(<\) & = & = \\ \hline \end{tabular}
\end{table} 
Table 4: Hot/cold heat transfer coefficient comparisons. \begin{table}
\begin{tabular}{l c c c} \hline  & **Cooled** & **Heated** & \(h\) **(Wm\({}^{-2}\)K\({}^{-1}\))** \\ \hline \multirow{4}{*}{\begin{tabular}{c} VWSG2 \\ (4 m depth) \\ \end{tabular} } & - & - & \(h=3\) \\ \cline{2-4}  & + & - & \(h=4\) \\ \cline{2-4}  & + & O & \(h=5\) \\ \cline{2-4}  & + & + & \(h=6\) \\ \hline \multirow{4}{*}{\begin{tabular}{c} VWSG3 \\ (6.5 m depth) \\ \end{tabular} } & - & O & \(h=3\) \\ \cline{2-4}  & + & + & \(h=4\) \\ \cline{2-4}  & + & + & \(h=5\) \\ \cline{2-4}  & + & ++ & \(h=6\) \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} VWSG4 \\ (10.5 m depth) \\ \end{tabular} } & - & - & \(h=3\) \\ \cline{2-4}  & - & - & \(h=4\) \\ \cline{2-4}  & - & O & \(h=5\) \\ \cline{2-4}  & O & O & \(h=6\) \\ \hline \multirow{4}{*}{
\begin{tabular}{c} VWSG5 \\ (16.5 m depth) \\ \end{tabular} } & - & - & \(h=4\) \\ \cline{2-4}  & O & O & \(h=5\) \\ \cline{2-4}  & + & O & \(h=6\) \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._cold-contraction happen on the whole concrete body; therefore, the expansion/contraction is greater at the pile section with a larger diameter. As a result, the effect of expansion/contraction should be more significant at VWSG 1 and 2 than at VWSG 4 and 5. 3. There are different types of soil. At the depth of VWSG 1 and 2, the soil is \"made ground\", while at the depth of VWSG 4 and 5 the pile is surrounded by London Clay. The material \"made ground\" is set to have a thermal conductivity of 2.5 Wm\({}^{-1}\)K\({}^{-1}\), while London Clay has a value of 1.7 Wm\({}^{-1}\)K\({}^{-1}\). This means the heat transfer efficiency is higher at the depth of VWSG 1 and 2 than VWSG 4 and 5. For the borehole that is some distance away from the test pile (0.5 m), the borehole temperature can be more sensitive at VWSG 1 and 2 than 4 and 5. This is another possible reason for the quite small \(h\) difference in VWSG 4 and 5 figures. The result of VWSG3 is obviously against the hypothesis made in this chapter. However, it was noticed that VWSG3 acted different from all the other devices. It was the only VWSG to give a matched curve in the heating mode period with \(h=3\) Wm\({}^{-2}\)K\({}^{-1}\). For all the other instruments, the appropriate \(h\) for the hot mode was 5-6 Wm\({}^{-2}\)K\({}^{-1}\). It can be assumed that there are some special underground circumstances at the depth of VWSG3 (for example ground water flows) so that the heat transfer at that depth is abnormal compared to the whole pile.