THE THERMAL POTENTIAL OF AN EARTH TUBE HEAT EXCHANGER SYSTEM IN AIR TEMPERATURE MODERATING

Document Type : Original Article

Authors

1 Assistant prof. , Agric. Eng. Dept. Faculty of Agric, Kafrelsheikh University. Egypt.

2 Prof., Agric. Eng. Dept. Faculty of Agric, Kafrelsheikh University., Egypt.

3 Graduate Student, Agric. Eng. Dept. Faculty of Agric, Kafrelsheikh University. Egypt.

Abstract

The potential of earth tube heat exchangers in tempering ventilation air in delta region was studied experimentally by using two diffident systems. The two systems were installed at the research farm, faculty of agriculture, Kafrelsheikh University (31.07° N and 30.57° E), Kafrelsheikh governorate, Egypt. The first system (S1) consisted of one pipe with inner diameter of 10.85 cm. The second system (S2) consisted of two coaxial pipes the first pipe with inner diameter of 10.85 cm surrounded by the other one with inner diameter of 16.2 cm and the annular space between them filled by water and sealed. The length of both systems was 12 m and buried at a depth of 75 cm within two ditches 5 m apart and refilled with earth. The ambient air was blown by a 0.75 kW blower to pass through the two buried systems. The systems were operated during cooling and heating modes at four operating durations and five air velocities.  It was found that, the maximum temperature reduction and rise were 12.65 °C at air velocity 1.8 m/s, 12 hours operating duration and 6.27 °C at velocity 3.7 m/s, 12 hours operating duration under cooling and heating modes for S1 respectively.  Maximum thermal energy rate removed during cooling mode was 679.9 W for S2 at air velocity 9.7 m/s and 22 hours operating duration and the corresponding COP was 3.96. The maximum thermal energy rate added during heating mode was 629.7 W for S1 at air velocity 9.7 m/s, 12 hours operating duration and the corresponding COP was 3.67. Both systems contribute in air temperature control which declares in diminishing its amplitude. It was found that when the air velocity (mass flow rate) increase the thermal energy rate removed / added increases although the temperature reduction / rise decreases. This was because of the effect of increasing mass flow rate was predominant than the effect of temperature reduction/ rise in thermal energy rate exchanged evaluation.
Key words: Earth tube, thermal potential, earth to air heat exchanger

Main Subjects

References

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Misr Journal of Agricultural Engineering
Volume 34, Issue 3
July 2017
Pages 1437-1464

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