**2.3 Meshing**

The next step of the pre-processing stage is the generation of mesh to be used in the ANSYS ICEM is used for generating the mesh of the geometry. The tetrahedral meshing is used to mesh the heat exchanger for the earth-to-air model which is shown in **Figure 8**. Since air enters from the one end of the pipe this is the 'inlet' and leaves from the 'outlet' created in the model. In the present analysis, CFD simulations performed using an unstructured grid. The mesh is used proximity and curvature-based. One of the geometry meshing algorithms picks a different mesh method by default. The sizing parameters are selected based on the size of the model. The 'relevance centre' and 'smoothing'specification of each mesh is set to fine. The minimum element size and maximum element size both are set to 0.011 mm and 0.15 mm respectively.
