An experimental and a numerical study of horizontal earth-air heat exchanger in a hot climate

Figures & data

Figure 1. Schematic diagram of the system of EAHE.

Figure 2. Symmetrical Geometry of the exchanger under Gambit.

Figure 3. Various types of grid used for simulation.

Figure 4. Grid controls.

Figure 5. Iso-surfaces.

Figure 6. Profile of temperature of the ground for various depths (Khalajzadeh, Heidarinejad, and Srebric 2011).

Table 1. Physical properties (Moummi et al. 2010).

Properties	Values
Thermal conductivity of the ground (W/m. °C)	2.01
Specific heat of the ground (J/kg. °C)	1380
Density of the ground (kg/m^3)	2300
Thermal diffusivity of the ground (m^2/s)	6.33 × 10^−7
Thermal conductivity of the PVC (W/m. °C)	1.17
Specific heat of the PVC (J/kg. °C)	900
Density of the PVC (kg/m^3)	1380

Table 2. Parameters of input for the comparative validation (Moummi et al. 2010).

Properties	Values
Pipe length (m)	50
Pipe diameter (m)	0.11
Depth of pipe (m)	3
Air velocity (m/s)	4.5; 3.5
Inlet temperature (°c)	37,48
Soil temperature (z = 3 m) in summer (°C)	24; 28

Figure 7. Location of sensors along the heat exchanger.

Figure 8. Image of the horizontal heat exchanger for various depths.

Figure 9. Detailed site of the sensors of the air inside the sheath.

Figure 10. Comparison of inlet and the outlet temperature of the exchanger, for each month (a) July (b) August.

Figure 11. Variation in the temperature for different types of grids.

Table 3. Validation of the model of simulation (Temperature of the ambient air 37 °C, and Soil temperature (Z = 3 m) 24 °C).

Position of sensors (m)	Measured temperatures (°C)	Simulated temperatures (°C)
2.65	35.24	35.66
6.9	32.28	31.44
10.81	29.83	29.00
18	26.74	26.70
23.44	25.95	25.44
30.21	25.00	25.02
45.3	24.21	24.26

Figure 12. Distribution of the temperature of the air with the length of the conduits.

Figure 13. Distribution of the temperature on the wall of the conduits.

Figure 14. Validation of CFD results with experimental results.

Figure 15. Comparison of the results obtained by the use of the UDF with the experimental ones.

Table 4. Comparison enters the results simulated and the results obtaining by the UDF (Temperature of the ambient air 37 °C, and soil temperature (Z = 3 m) 24 °C).

Position of sensors (m)	Measured temperature (°C)	Simulated temperatures (°C)	Corrected and simulated temperatures (°C)	Absolute error of the simulated temperature	Absolute error of the simulated temperature corrected	Relative error ‘simulated temperature’	Relative error « simulated temperature corrected »
6.900	32.283	31.440	32.503	0.843	0.220	2.86%	1.12%
10.810	29.830	29.000	29.500	0.83	0.330
14.140	27.974	28.400	28.000	0.426	0.026
18.000	26.745	26.700	26.982	0.045	0.237
22.030	26.356	26.127	26.127	0.229	0.229
23.440	25.954	25.440	25.844	0.514	0.110
26.170	25.327	25.130	25.427	0.197	0.100
34.100	24.809	24.400	24.654	0.409	0.155

Khalajzadeh, V., G. Heidarinejad, and J. Srebric. 2011. “Parameters Optimization of a Vertical Ground Heat Exchanger Based On Response Surface Methodology.” Energy and Buildings 43 (6): 1288–1294.10.1016/j.enbuild.2011.01.007

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Moummi, N., H. Benfatah, N. Hatraf, A. Moummi, and S. Youcef Ali. 2010. “Le Rafraîchissement par la Géothermie: Etude Théorique et Expérimentale dans le Site de Biskra.” Energies Renouvelables 13 (3): 399–406.

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