Abstract
This study proposed a Lining Borehole ground Heat Exchanger (LBHE) using thermosetting resin impregnated glass fiber. Some indoor and field tests were conducted to identify the thermal and strength properties of the LBHE, which are necessary for the practical application. In addition, Thermal Response Test (TRT) was conducted for the LBHE and a double U-tube heat exchanger in the field test. It is seen from the indoor tests that the warp-knitted glass fiber is strong enough to bear the water pressure to inflate during construction and has sufficient elastic property to fit the roughness of the inside borehole. Thermal conductivity of the LBHE (non-treated) and that of the LBHE mixed with a filler were 0.32 and 0.47 W/(mK), respectively. A 100 m long LBHE could inflate by water pressure and the inflated volume of the LBHE attained more than 70% of the borehole volume calculated by a diameter of casing rod. The thermal resistance of LBHE was 0.035 K/(W/m) from the TRT and was lower than that of the double U-tube heat exchanger. It is expected that the LBHE may have a higher heat exchange performance, compared to the double U-tube method.
