| Title |
An Long-Term Experimental Study on the Thermal Performances of Horizontal-type Geothermal Heat Exchanger installed in Building Foundation Slab |
| Authors |
Hwang Kwang-Il ; Kim Joong-Hun ; Shin Seung-Ho ; Kim Yong-Shik |
| Keywords |
Geothermal Energy ; Temperature Differences Energy ; Horizontal-type Geothermal Heat Exchanger(HGHEX) |
| Abstract |
This study is to analyze the operation performances of a horizontal-type geothermal heat exchanger(hereafter abbreviated as HGHEX) installed into the foundation slab of a complex-purposed building located at Seoul, and the HGHEX has been successfully operated for over 5 years. The performances changes are especially focused on this study at the points of the long-term operation accompanied with the changes from a consecutive operation method(hereafter abbreviated as COM) to a intermittence operation method(hereafter abbreviated as IOM). The geothermal system for this building is consisted with HGHEX(total 31,860m length), Ground-source heat pump(16 units), circulation pumps(8 units) etc. This geothermal system performs cooling and heating to the lobby(1st floor) and the community areas like health club(B1st floor). Inlet and outlet temperatures of HGHEXs from/to ground-source heat pumps are measured in August 2000 and July 2005 for summer seasons, and in November 2000 and January 2006 for winter seasons. Followings are the results.On a summer day, temperatures differences are almost similar between COM and IOM, but after 24 hours operation temperatures are increased to 0.5~1℃ by COM comparing to the IOM. And a seasonal heat flux to the ground by COM is 2 times more than IOM. On a winter season, temperatures differences are neglectable on COM, but 0.5~1.5℃ of differences are happened on IOM, but after 24 hours operation temperatures are decreased to -2.5~-1.8℃ by COM comparing to -0.2~ 0.0℃ by IOM. But a seasonal heat flux from the ground by IOM is 3.4 times more than COM. At the point of annual-based total heat flux(heat exchanges) to/from the ground, COM exchanged 1.6 times more than IOM, but the ratio of in-flux to out-flux is 4.5% by COM and 31.3% by IOM. As a conclusion of this study, COM is suitable for a building of which load is biased to one the specified-load(cooling or heating), and must have sufficient refresh periods for up/down to the design conditions. On the other hands, it is clear that IOM is more efficient for a building of which heating and cooling loads are periodically balanced. |