Thermodynamic analysis of a ground-source heat pump system for district heating

This study deals with the thermodynamic analysis of ground-source heat pump (GSHP) systems for district heating. The mass, energy, entropy and exergy balance relations are derived and applied to a GSHP system with a U-bend ground heat exchanger. The performance characteristics of this GSHP system are evaluated in terms of energetic and exergetic aspects. Based on the measurements conducted on 7 January 2004, the heat extraction rate from the soil is found to be, on average, 61.4 W m−1 of bore depth, while the required borehole length in meter per kW of heating capacity is obtained as 11.71. The entering water temperature to the unit is measured to be 15.3°C. The heating coefficient of performance of the heat pump (COPHP) is about 2.85, while that for the whole system is obtained to be 7.4% lower than COPHP. The exergy efficiency values for the heat pump unit and whole system are found to be 66.8 and 66.6%, respectively.