Investigation of the Efficiency of the Earth-Air Spiral Heat Exchanger in Providing Part of the Heating and Cooling loads of a Building

The use of fossil fuels to supply energy to the buildings is associated with many constraints, including the reduction of  the resources and the environmental degradation, and the use of free and renewable sources of energy is noteworthy to provide the heat needed for the buildings. One of the free, clean and renewable energy sources is the energy in the underground layers of Earth. Although the soil temperature in the surface layers may be influenced by the temperature of the environment, the temperature during the year at sublayers is almost constant, and in the summer the temperature of the soil is lower and in winter it is higher than the ambient air temperature. This potential can be used for the cooling and heating of buildings. In this research, the spiral coiled tube air-earth heat exchanger has to be evaluated and its performance in Tehran should be evaluated. Three dimensional, steady state numerical simulations are performed using Ansys-Fluent software. The system is simulated in two heating and cooling modes, and the results are expressed as an increase or decrease in the temperature of the inlet air. The effect of factors such as the depth of the buried heat exchanger in the soil, the speed and temperature of the inlet air on the exhaust air temperature and the thermal load absorbed by the heat exchanger are investigated. While the burst depth of the heat exchanger increases the heat transfer, the increase in the air inlet velocity reduces the heat exchange between the soil and the air. Investigations show that the spiral heat exchanger can increase up to 15 ° C of the air inlet temperature to the building during the winter.