Ground-air heat exchangers (GAHXs) play an important part in the geothermal technology applications. For many applications, the difference between the ambient air and ground temperatures is an important limit factor in the system's performance, as it is relatively unchanged throughout the day. To maximize this temperature difference, optimization of the pipe wall area for enhanced convective heat transfer, while maintaining a short pipe length was conducted. This includes the generation of turbulence within the fluids with special inserts, and the selection of different materials of distinct thermal conductivities. In this paper, the plate-inserted pipe is tested and verified against the regular smooth pipe for the enhancement in the air temperature drop through the pipe during the summer days. A detailed computational fluid dynamics (CFD) model was established and validated using the experimental data. Good agreement between computational and experimental data are obtained. The numerical results also shown that when the plates are added, the temperature difference is much improved with reasonable pressure drop.