Thermal Efficiency Comparison of Borehole Heat Exchangers with Different Drillhole Diameters

Energies

Jin Luo¹  Joachim Rohn¹  Manfred Bayer² 

[1] GeoZentrum Nordbayern, Friedrich Alexander University Erlangen Nuremberg, Bayern 91054, Germany; E-Mails:;TÜV Rheinland, LGA Bautechnik GmbH, Tillystr. 2, 90431 Nuremberg, Germany; E-Mail:

关键词: ground source heat pump system;    borehole heat exchanger;    drillhole diameter;    thermal efficiency;   

DOI  :  10.3390/en6084187

来源: mdpi

【 摘 要 】

Thermal efficiency of borehole heat exchangers (BHE) is of crucial importance for the design and optimization of ground source heat pump (GSHP) system. This paper investigates thermal efficiency of a BHE with three drillhole diameters: 121mm, 165mm and 180mm. The BHE was installed in a GSHP system of an office building located in Nuremberg,Germany. Thermal properties and hydraulic properties of the ground where the BHE was installed have been measured by thermal response tests as well as pumping tests. Furthermore, the evaluation of thermal performance is made possible by monitoring operation of the GSHP system. Using the recorded data, thermal exchange rates have been calculated and compared in a daily period as well as a seasonal period. The daily statistics indicate that the thermal exchange rate of the BHE increases with larger drillhole diameter. For the seasonal cooling performance, the amount of thermal exchange of BHE with 165 mm and 180mm diameters was found to be 3.2% and 7.1% larger than that of the BHE with 121mm diameter, respectively. These findings provide helpful suggestions for the design of future GSHP systems to achieve higher energy-efficiency.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.