The objective of this study is to develop a novel thermal response test (TRT) equipment that can be applied to existing water wells instead of borehole heat exchangers (BHEs). Accordingly, field tests were conducted using new and conventional equipment to estimate the vertical distribution of ground thermal conductivity. The result showed that the estimated thermal conductivity profile was higher than the reference profile obtained using conventional equipment. The temperature behavior in the well was considered to be unstable due to natural convection because the heating time was 4 hours, which is not long enough. Next, a numerical model of the water well including the novel equipment was developed, and the model was validated through history matching by using the temperature change in each depth. Finally, the TRT was simulated for two days using the model, and the simulated thermal conductivity profile was similar to the reference profile except near the end of the heated section. This result indicates that a more accurate thermal conductivity profile can be obtained by increasing the heating time until approximately 1.5 days.