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 degrees 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. Copyright (c) 2005 John Wiley & Sons, Ltd.