Energy and exergy analyses of a helicoidal water to air geothermal heat exchanger for arid regions

Helicoidal water-air geothermal heat exchanger (HWAGHE) uses the water well as a heat source/sink for air refreshing purposes in space. It has been exploited as a passive technique to minimize the energy uses in buildings. This work goals to estimate the energy and exergy characteristics of HWAGHE for arid zone weather condition of Algeria. The helicoidally geometry enhancing the heat exchange with the soil is chosen to decrease the operating cost and the needed area. The studied HWAGHE was constructed from a flexible PVC pipe with 30 m length and 0.6 m diameter. It was immersed into a drilled borehole with 1 m diameter and 5 m depth. The heat exchange rate with the ground and exergy and energy efficiencies of HWAGHE is evaluated. Experimental findings revealed that the inlet ambient temperature has a considerable impact on the HWAGHE performances mainly when the change in temperature between the ambient and the water well increments. Maximal exergy and energetic efficiencies of the HWAGHE, reaching 89% and 92%, respectively, are obtained at 0.035 kg s−1 mass flow rate.