In this paper, the thermal performance of an Earth-Air Heat Exchanger (EAHE) used for heating and cooling
purposes is investigated under Egyptian weather conditions. The soil temperature profile and the
temperature distribution of flowing air through horizontal Earth-Air Heat Exchanger (EAHE) is experimentally
studied. Also, a mathematical model based on unsteady, one-dimensional and quasi-state is
developed for energy conservation equation. Moreover, an explicit finite difference numerical method
is used to solve the developed mathematical model with the help of MATLAB code. Finally, threedimensional,
steady and double precision Computational Fluid Dynamics (CFD) ANSYS Fluent simulation
model is established to predict the air and soil temperature. Whereas, the standard j 2 model is applied
to simulate the turbulence kinetic energy of the flowing fluid. The mathematically developed model and
CFD simulation result validated against experimental results. Good agreement is achieved with an average
error and correlation coefficient of 2.09, 97% and 3.3 and 95.5% for CFD simulation and mathematical
model respectively. The CFD model is used in a parametric investigation. A parametric study carried out
to explore the impact of different parameters such as pipe diameter, pipe material, pipe space, pipe length
and flowing fluid velocity. The results show that some of these parameters have noticeable results in air
temperature. Whereas, the pipe diameter increases the air temperature decreases. The outlet air temperature
declines from 20.4 C to 18.7 C as the pipe diameter expands from 2 to 3 in. Furthermore, as pipe
length increases, outlet air temperature enhances. The temperature changes from 19.7 to 19.9 C as the
pipe length elongates from 5.45 m to 7 m. A bit change occurs in outlet air temperature from 19.7 C to
19.8 C when pipe space changes from 0.2 to 0.5 m. Moreover, three different pipe materials such as PVC,
steel and copper are implied. The outlet air temperature was 19.7 C in PVC pipe and 19.8, 19.8 C for steel
and copper respectively. So the conclusion is that the change in outlet air temperature for various pipe
material is neglected compared with their prices. Finally, the effect of fluid velocity was investigated.
Therefore, the outlet air temperature declines from 20.4 C to 19.2 C as air accelerates from 1 to 3 m/s |
