Dynamic simulation of a qanat source heat pump in different climatic conditions

In this study, the year-round thermal performance of a qanat source heat pump in supplying the required cooling and heating loads of a case study building is investigated. Using TRNSYS software, dynamic simulation of the proposed system is performed in three climate zones including Hot/Dry, Cold/Dry, and Hot/Humid. The heat pump and helical coil heat exchanger inside the qanat water are mathematically modeled in MATLAB, and then, coupled to TRNSYS model to evaluate the system transient performance. It is found that the free energy ratio of the qanat source heat pump Hot/Dry climate zone is on average 21.6% higher than compared to that of the air source heat pump. In cold months, by increasing the temperature of the inlet fluid to the helical coil heat exchanger inside the qanat, the system coefficient of performance increases 15%. The increase of the energy efficiency ratio of the system in the warm months is 7.7%. It is also found the highest coefficient of performance and the lower energy efficiency ratio of the system is obtained in the Hot/Humid climate zone in comparison with the other zones; so that, the energy efficiency ratio of the system in the Cold/Dry and Hot/Dry zones is 48% and 58% higher than that in the Hot/Humid zone, respectively. The annual FER of 63.4%, 63.1%, 56.8%, and 53.3% are obtained in Hot/Dry (Kerman), Cold/Dry (Mashhad), Hot/Dry (Tehran), and Hot/Humid (Bandar Abbas), respectively. These findings suggest that the building energy consumption significantly reduces using the QSHP in all climatic conditions.