The effect of different pitch and tube arrangement on the thermal performance of earth-air heat exchanger (EAHE) is numerically simulated to get the optimized length of the EAHE. In the present study, three different tube arrangements (U-shaped, double U-shaped and helical coil) numerically investigated with ANSYS Fluent 20.1 solver at different Reynold's number (Re = 15000 − 25000). The ambient air at T = 313 K is circulated through the different tube arrangement buried under the soil which kept at T = 298 K. The diameter tube and total length of the tube of EAHE are 10.1 cm and 40 m respectively considered. The velocity is varied from 2.19 m/s − 5.11 m/s. The thermal performance of these configurations are compared at fixed Re = 15000. It is found the helical coil earth-air heat exchanger has pronounced effect over the U-shaped and double U-shaped heat exchanger. It also seen that the thermal performance of the earth-air heat exchanger is optimum at the low Reynold number (Re = 15000) in all the configurations. Thus, the optimized length obtained in the helical earth-air heat exchanger further used to study the effect of pitch on the flow behavior and heat characteristic. Three different pitches of 0.5 m, 1.0 m, and 1.5 m were considered to get the thermal performance of EAHE. It is found that air temperature reaches to the soil temperature (T = 298 K) at distance of 25.94, 18.324, and 20.37 m from inlet for the helical pipe of pitch 0.5 m, 1.0 m and 1.5 m respectively.