20 September 2011

NUMERICAL SIMULATION OF VERTICAL GROUND HEAT EXCHANGERS FOR GROUND SOURCE HEAT PUMPS


This paper presents the numerical simulation of several types of vertical ground heat exchangers. The ground heat exchangers (GHEs) such as U-tube, double-tube and multi-tube were simulated using the commercial CFD software FLUENT. Water flows through
the heat exchangers and exchanges the heat to the ground. The inlet and outlet water temperatures, flow rate, and heat exchange rate are presented. The heat exchange rates in discontinuous short-time period of operation namely 2 h operation-time and 2 h off-time and continuous operation are investigated and compared with that of the experimental results. Comparing numerical results with experimental results shows that the numerical models are capable to determine the GHE performances. The heat exchange rate in discontinuous
operation increased compared with that of in continuous operation. As an example, the heat exchange rate of the discontinuous operation at 22 h increases of 17.1 % for U-tube, 22.5 %
for double-tube, and 16.5 % for multi-tube compare with that of the continuous operation at the same time. In addition, heat exchange process in the off-time increases the heat
exchange rate of GHEs.