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    ThesisItemOpen Access
    Simulation of heating and cooling of agricultural greenhouse using geothermal energy
    (Punjab Agricultural University, Ludhiana, 2016) Namgial, Deldan; Aggarwal, Rajan
    The Earth Tube Heat Exchanger (ETHE) system was installed at the research field of Department of Soil and Water Engineering, Punjab Agricultural University, Ludhiana, India. The soil temperature was monitored upto 3.5 m from April 2013 to March 2014. The ETHE was designed and installed based on deep soil temperature and heating load of greenhouse. The ETHE consists of 42 m long PVC pipe of 0.25 m diameter buried at 3.5 m depth. The air was circulated with belt driven force drive centrifugal blower (radial blade) attached with 3 phase 10 hp motor. The ETHE was operated at velocity ranging from 2.3 to 24 m/s under open and closed system for winter heating from Oct 2014 to Feb 2015. It was also operated under open, closed and naturally ventilated system for summer cooling from April to June 2015. The thermal parameters viz. heating/cooling potential, Coefficient of Performance (COP) and tube efficiency were evaluated at different velocities and durations. In all ETHE systems it was observed that as velocity increased the temperature difference between inlet and outlet decreased. The mean heating potential, COP and tube efficiency under open system was higher than closed system in each set of velocity during peak winter. But the cooling potential, COP and tube efficiency under closed system was higher than open and naturally ventilated system during peak summer. The cooling potential, COP and tube efficiency during peak summer were higher than peak winter. However, the performance of greenhouse coupled with ETHE during peak winter was better than peak summer. Therefore, the study revealed that thermal parameters are not proportional to performance of greenhouse coupled with ETHE. The ETHE inlet and outlet temperatures recorded during ETHE operation were used to calibrate and validate the FLUENT model. The low value RMSE and percent error and high correlation coefficient during validation indicate reasonably accurate simulation of ETHE outlet temperature by the model. The parametric analysis revealed that ETHE performance increased with decreased in velocity and diameter of pipe and increased in buried depth and length of pipe.