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Energetic performance test of an underground air tunnel system for greenhouse heating

Leyla Ozgener and Onder Ozgener

Energy, 2010, vol. 35, issue 10, 4079-4085

Abstract: The main objective of the present study is to investigate the performance characteristics of an underground air tunnel (UAT) for greenhouse heating with a 47m horizontal, 56cm nominal diameter U-bend buried galvanized ground heat exchanger. This system was installed in the Solar Energy Institute, Ege University, Izmir, Turkey. Based upon the measurements made in the heating mode, the average heat extraction rate to the soil is found to be 3.77 kW, or 80.21W/m of tunnel length, while the required tunnel length in meters per kW of heating capacity is obtained as 12.46. The entering air temperature to the tunnel ranges from 14.3 to 21.5°C, with an average value of 15.5°C. When the system operates, the greenhouse air is at a minimum day temperature of 13.1°C with a relative humidity of 32%. The maximum heating coefficient of performance of the UAT system is about 6.42, while its minimum value is about 0.98 at the end of a cloudy and cold day and fluctuates between these values at other times. The daily average maximum COP values for the system are also obtained to be 6.42. The total average COP in the heating season is found to be 5.16.

Keywords: Energy; Geothermal energy; Underground air tunnel (search for similar items in EconPapers)
Date: 2010
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Handle: RePEc:eee:energy:v:35:y:2010:i:10:p:4079-4085