Influence of an internal heat exchanger on the operation of a CO2 direct expansion ground source heat pump

In this work, the influence of an internal heat exchanger (IHE) on the operation of a CO 2 direct expansion ground source heat pump (DX-GSHP) was assessed through transient energy simulations. A previous theoretical model was extended to account for an IHE, and was used to evaluate the performance of DX-GSHP systems under various controls, ground conditions and building loads. A showcase of the benefit of integrating an IHE to the DX-GSHP was carried out, through 4-month heating energy simulations period of a small residential building located in Canada, under 4 different cases. Results show that adding an IHE to the system effectively counters the effect of thermal short-circuiting in the borehole as well as ground surface temperature variations, and thereby increases its efficiency. Crown Copyright (C) 2019 Published by Elsevier B.V. All rights reserved.