Earth-to-air Heat Exchanger for Cooling Applications in a Hot and Dry Climate: Numerical and Experimental Study

Document Type : Original Article


1 Mechanical Engineering Department, Microfluidics and MEMS lab, Babol Noshirvani University of Technology, Babol, Iran

2 Mechanical Engineering Department, Babol Noshirvani University of Technology, Babol, Iran

3 Principal planner at Prince Williams County, State University of New York, College of Environmental Science and Forestry, United States of America


Shallow geothermal energy, by an earth-to-air heat exchanger (EAHE), is utilized to cool buildings with minimal energy usage. Significant parameters affecting the heat exchanger's performance must be investigated to obtain a suitable design. Shallow geothermal energy, by an earth-to-air heat exchanger (EAHE), is utilized to cool buildings with minimal energy usage. Significant parameters affecting the heat exchanger's performance must be investigated to obtain a suitable design. This article numerically and experimentally investigates the effect of pipe diameter, pipe length, inlet air temperature, soil temperature, airflow velocity, and soil thermal conductivity on the performance of the heat exchanger under hot and dry climate conditions. The soil temperature distribution was measured from the surface to a depth of 7 m in the city of Karbala (center of Iraq) in the summer season. The experimental test for EAHE was carried out in water-saturated soil and ambient air temperatures of 41 ºC, 45 ºC, and 49.5 ºC at four different velocities. The percentage drop in the EAHE outlet air temperature at 9 m/s was 28.3%, 25.5%, and 19.5%, respectively. Also, the three-dimensional model was created, and the simulation results were compared with the experimental results, which were in good agreement. An equation for the outlet air temperature was found as a function of pipe diameter and length, ambient air temperature, soil temperature around the pipe, and soil thermal conductivity. The resulted equation were compared with the current experimental results and experimental results of reported data inliterature. As a result, a very good agreement was observed. The results showed that the parameter L (length of the pipe) causes the strongest nonlinear behavior in the equation. For the cases considered, at diameters 75 and 100 mm, an approximate linear behavior for the length required to achieve a specific outlet temperature was observed. It can be concluded from the results that changing the soil type from dry one (k=0.5 W/m K) to saturated one (case of Karbala city, k=1.5 W/m K) resulted about 25% reduction in the length of the pipe. Also, the results showed that at an air velocity of 7m/s, the length required to obtain 26 ºC at the outlet of EAHE is 62.1 m which is 55% higher than the case of 29 ºC (39.9m).


  1. IEA, I. “World energy outlook 2011.” International Energy Agency, Vol. 666, (2011).
  2. Chen, H., Ooka, R., Huang, H., and Tsuchiya, T. “Study on mitigation measures for outdoor thermal environment on present urban blocks in Tokyo using coupled simulation.” Building and Environment, Vol. 44, No. 11, (2009), 2290-2299.
  3. Ben Jmaa Derbel, H., and Kanoun, O. “Investigation of the ground thermal potential in tunisia focused towards heating and cooling applications.” Applied Thermal Engineering, Vol. 30, No. 10, (2010), 1091-1100.
  4. Alrwashdeh, S. S., Ammari, H., Madanat, M. A., and Al-Falahat, A. M. “The effect of heat exchanger design on heat transfer rate and temperature distribution.” Emerging Science Journal, Vol. 6, No. 1, (2022), 128-137.
  5. Mostafaeipour, A., Goudarzi, H., Khanmohammadi, M., Jahangiri, M., Sedaghat, A., Norouzianpour, H., Chowdhury, S., Techato, K., Issakhov, A., Almutairi, K., and Hosseini Dehshiri, S. J. “Techno-economic analysis and energy performance of a geothermal earth-to-air heat exchanger (EAHE) system in residential buildings: A case study.” Energy Science and Engineering, Vol. 9, No. 10, (2021), 1807-1825.
  6. Popiel, C. O., Wojtkowiak, J., and Biernacka, B. “Measurements of temperature distribution in ground.” Experimental thermal and fluid science, Vol. 25, No. 5, (2001), 301-309.
  7. Al-Ajmi, F., Loveday, D. L., and Hanby, V. I. “The cooling potential of earth-air heat exchangers for domestic buildings in a desert climate.” Building and Environment.
  8. Lu, S., Ren, T., Gong, Y., and Horton, R. “An Improved Model for Predicting Soil Thermal Conductivity from Water Content at Room Temperature.” Soil Science Society of America Journal, Vol. 71, No. 1, (2007), 8-14.
  9. Song, Y., Yao, Y., and Na, W. “Impacts of Soil and Pipe Thermal Conductivity on Performance of Horizontal Pipe in a Ground-source Heat Pump.” China Renewable Energy Resources and a Greener Future, Vol. 8, No. 2, (2006), 2-7. Retrieved from
  10. Omer, A. “Soil thermal properties: Effects of density, moisture, salt concentration and organic matter.” Advances in Science, Technology and Innovation, (2018), 113-114.
  11. Agrawal, K. K., Misra, R., Yadav, T., Agrawal, G. Das, and Jamuwa, D. K. “Experimental study to investigate the effect of water impregnation on thermal performance of earth air tunnel heat exchanger for summer cooling in hot and arid climate.” Renewable Energy, Vol. 120, (2018), 255-265.
  12. Abbaspour-Fard, M. H., Gholami, A., and Khojastehpour, M. “Evaluation of an earth-to-air heat exchanger for the north-east of Iran with semi-arid climate.” International Journal of Green Energy, Vol. 8, No. 4, (2011), 499-510.
  13. Singh Bisoniya, T., Kumar, A., and Baredar, P. “Parametric Analysis of Earth‐Air Heat Exchanger System Based on CFD Modelling,” Vol. 1, (2014).
  14. Khabbaz, M., Benhamou, B., Limam, K., Hollmuller, P., Hamdi, H., and Bennouna, A. “Experimental and numerical study of an earth-to-air heat exchanger for air cooling in a residential building in hot semi-arid climate.” Energy and Buildings, Vol. 125, (2016), 109-121.
  15. Serageldin, A. A., Abdelrahman, A. K., and Ookawara, S. “Earth-Air Heat Exchanger thermal performance in Egyptian conditions: Experimental results, mathematical model, and Computational Fluid Dynamics simulation.” Energy Conversion and Management, Vol. 122, (2016), 25-38.
  16. Hasan, M. I., Noori, S. W., and Shkarah, A. J. “Parametric study on the performance of the earth-to-air heat exchanger for cooling and heating applications.” Heat Transfer - Asian Research, Vol. 48, No. 5, (2019), 1805-1829.
  17. Yamini, O. A., Mousavi, S. H., Kavianpour, M. R., and Ghaleh, R. S. “Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling.” Advances in Civil Engineering, Vol. 2021, (2021).
  18. Misra, R., Aseri, T. K., and Bansal, V. “Cfd analysis of thermal influence zone of earth air tunnel heat exchanger under transient conditions.” 14th International Conference of IBPSA - Building Simulation 2015, BS 2015, Conference Proceedings, No. 1991, (2015), 1655-1662.
  19. Gauthier, C., Lacroix, M., and Bernier, H. “Numerical simulation of soil heat exchanger-storage systems for greenhouses.” Solar Energy, Vol. 60, No. 6, (1997), 333-346.
  20. Wilcox, D. C. “Formulation of the k-ω turbulence model revisited.” AIAA Journal, Vol. 46, No. 11, (2008), 2823-2838.
  21. Yamini, O. A., Movahedi, A., Mousavi, S. H., Kavianpour, M. R., and Kyriakopoulos, G. L. “Hydraulic Performance of Seawater Intake System Using CFD Modeling.” Journal of Marine Science and Engineering, Vol. 10, No. 7, (2022).
  22. Lu, Y., Lu, S., Horton, R., and Ren, T. “An Empirical Model for Estimating Soil Thermal Conductivity from Texture, Water Content, and Bulk Density.” Soil Science Society of America Journal, Vol. 78, No. 6, (2014), 1859-1868.