24 June 2014
In vertical ground source heat pump applications, usually a single-U tube is used in a borehole. In some studies, double U-tube is suggested to improve the heat transfer rate per unit length of borehole. Therefore a cost and performance analysis for multi U-tube
applications in a borehole is needed to determine the net benefit. In this study, a triple U-tube is inserted in a 50m borehole. Heat transfer rate per unit length of the borehole is
experimentally measured when single, double and triple U-tubes are in operation separately. Experimental measurements showed that increment of number of U-tubes in a borehole
increases performance of the borehole considerably. The relation between number of U tubes and heat transfer rate per unit length is analyzed. Long term borehole performance
predictions are made and compared for single, double and triple U tube applications.