**2.2 Model specifications**

The present CFD EATHE model is prepared by using CATIA P3 V5R14. The CATIA is a very important tool for preparing geometry. Since the EATHE model is cylindrical. The model has been considering three parts via outer, middle and, inner which are the material of soil, PVC pipe, and air (fluid) respectively. There are three types of model straight pipe, spiral pipe, and helical pipe heat exchanger for the earth-to-air model which is shown in **Figures 2**–**7**.

**Figure 2.** *Straight pipe heat exchanger for earth to air.*

**Figure 3.** *Model of straight pipe EATHE.*

**Figure 6.**

**Figure 7.**

**269**

*Model of helical pipe EATHE [8].*

**Figure 5.**

*Model of spiral pipe EATHE.*

*Earth Air Tunnel Heat Exchanger for Building Cooling and Heating*

*DOI: http://dx.doi.org/10.5772/intechopen.99348*

*Helical pipe heat exchanger for earth to air.*

**Figure 4.** *Spiral pipe heat exchanger for earth to air.*
