Development and validation of a custom-built ground heat exchanger model for a case study building

• Examination of the custom-built ground heat exchanger (GHX).
• The first model for a custom-built GHX to calculate entering water temperatures.
• Model validation against the measured data from a real building.

Use of a ground-source heat pump (GSHP) system is becoming widespread in energy savings applications. A typical GSHP system is equipped with one of three ground heat exchanger (GHX) configurations: vertical, horizontal, or surface-water. Due to site characteristics/limitations, however, some residential/commercial buildings utilize a combination of different GHX configurations for their GSHP systems; in this research, we will refer to such a system as a custom-built GHX. A residential building utilizing a custom-built GHX combining two different GHX types (horizontal and surface-water) was selected to be the case study for this research. This research developed a custom-built GHX model to calculate the entering water temperatures (EWTs) circulated from the custom-built GHX to the GSHP system. In order to validate the developed model, the measured EWTs from the case-study house were referenced and compared to the calculated EWTs. The comparison showed that the average EWT differences resulted in about 1.2 °C (2.1 °F) and 1.6 °C (2.8 °F) for the full heating and cooling seasons, respectively.