Geothermal helical heat exchanger

This paper presents helical heat exchangers for geothermal use. The differences with more widespread geothermal exchangers are given, and a complete thermal model for the underground such as for the exchanger is developed, including the local freezing of water contained in the underground when temperatures are lower than 0◦C. This model is com-pared with published data and with experimental re-sults. In a second part, the model is applied to the heating and the cooling of buildings. The choice was made to consider that the thermal energy needed was directly extracted from the underground, so that results do not depend on the model of heat pump.