SIMULATION OF GROUND THERMO-PHYSICAL CAPACITY FOR A VERTICAL CLOSED-LOOP GROUND-COUPLED HEAT PUMP SYSTEM

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7408-07-2 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 42, 557-566 pp, DOI: 10.5593/sgem2017/42/S17.070

ABSTRACT

The ground serves as an ideal heat source for monovalent ground-coupled heat pump (GCHP) systems. This paper presents a working methodology and develops an analytical model for evaluation of the ground thermal conductivity and the borehole thermal resistance using a thermal response test (TRT). Additionally, this paper uses the Earth Energy Designer (EED) simulation program developed on the basis of the line-source model to calculate the fluid temperature for a case study of the ground heat exchanger according to the monthly heating and cooling loads and the borehole thermal resistance. Through the ground TRT, the length of the loops is properly determined, the operating performance of the system is provided, and supplementary costs (e.g. extra loops, boreholes, glycol, etc.) are avoided. The average fluid temperature in the ground for cooling, heating and domestic hot water production thermal power over a period of 25 years was simulated. Analysing the time evolution of the fluid temperatures in the ground for the peak loads reveals that these values are approximately constant, meaning that the heat source (ground) is fully regenerated and thus the GCHP will maintain high performance in operation.

Keywords: heat pump, ground-source, borehole heat exchanger, thermal response test, EED simulation program