**3.2 Validation of model to experimental data**

A CFD-based EATHE model was developed to forecast the thermal performance of the EATHE system. The developed CFD model was validated using the previously published results by Bansal et al. [3]. They conducted the experiments to determine the cooling performance of the EATHE system for the hot and dry climate of Ajmer (Western India) with pipes of two different materials-PVC and mild steel. Both the pipes have 0.15 m inner diameter, 23.42 m length, and were enshrouded 2.7 m below the ground surface in the horizontal position. The properties of air, soil and PVC is shown in **Table 3**. Experimental and simulation temperature results along the pipe length for PVC pipe at a velocity of 5 m/s are shown in **Figure 10**. The temperature predicted by the CFD model at all the points, except at the inlet point, along the pipe length is lower than the experimental results. It is also observed that temperature deviation varies between 0% to a maximum of 7.62%, and this deviation in temperatures may be contributed by the variation in the coefficient of friction (from actual friction coefficient of pipe) used in a simulation for the pipe material.
