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Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Energy shortage and environmental pollution have led to the wide use of clean and renewable energy. A ground source heat pump (GSHP) is extensively utilized in the new building of various renewable energy, because of its energy saving, high efficiency and environmental friendliness. However, the current GSHP development is limited to a certain extent, due mainly to its high cost, and large land areas resulting from drilling boreholes. Alternatively, the concept of an energy pile was proposed to combine the GSHP exchanger of ground heat with the pile foundation of a building. However, the temperature change of pile body can result in the thermal expansion and contraction of an energy pile, thereby to induce the pile deformation in the actual operation of energy piles. This variation of temperature has endangered the structural safety of energy piles, particularly on the thermal performance and bearing capacity. Therefore, a feasible energy pile with phase change concrete has been selected, where a type of phase change material (PCM) can serve as a part of filling material in a traditional energy pile. The thermal performance of the energy pile with phase change concrete was greatly enhanced, indicating the weak temperature variation and deformation during the heat exchange, due largely to the invariable temperature and the latent heat release during the phase change of PCM. In this study, a 3D numerical model of energy piles with phase change concrete was established to evaluate the thermo-mechanical characteristics of a whole energy pile under thermal-mechanical coupling loads. A systematic analysis was made to compare the thermo-mechanical characteristics of traditional energy pile and the new one with phase change concrete. An experiment was conducted to explore the effects of the distance between two legs of U-tube, and the ratio of length to diameter of pile body on the thermo-mechanical behavior of an energy pile with phase change concrete. The results showed that the solid-liquid phase change of PCM increased the heat exchange rate at the per unit depth of pile by 10.3%, while reduced the changes in the temperature of pile body. There was a reduced changes in the displacement, axial force, and side friction resistance of pile body that caused by the temperature change. With the increase of distance between two legs of U-tube, the heat transfer rate and heat influence range of soil increased in the energy pile, while the axial force of the pile decreased, as well as the pile displacement first increased and then decreased. An increase in the ratio of length to diameter improved the total heat exchange rate of energy piles, but reduced the heat exchange rate at the per unit depth of pile, while increased the pile top displacement, which was not conducive to the stability of the energy pile. The experimental validation showed that the predicted relative errors of middle temperature in the pile wall and displacement at the pile top were within 5.1% and 12%, respectively, and the average relative errors were 4.2% and 9.9%, respectively. Therefore, the developed numerical model of an energy pile can be used to simulate the thermo-mechanical characteristics of an energy pile with phase change concrete. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The new trends in energy savings and greenhouse gas reductions are expecting to explore the utilization of shallow geothermal energy. The most popular way to exploit shallow geothermal energy resources is the ground coupled heat pump (GCHP) system with using ground as a heat source. Because underground temperature is rather constant compared with ambient air temperature, the GCHP could achieve higher efficiency as well as more stable performance compared with traditional air source heat pumps. Thus the GCHP system becomes increasingly popular in commercial and institutional buildings. In general, a vertical borehole with ground heat exchanger (GHE) is used as the mainstream of GCHP system. However, the wide application of this type of GCHP technology has been limited by its higher initial cost and substantial land areas required to install the GHE. For this reason, the foundation piles of buildings have been used as part of GHE in recent years to reduce the cost of drilling borehole and save the required land area. This innovative idea of utilizing what are usually called “energy piles”, has led to notable progress in the field of GCHP systems. It has become particularly attractive because it lowers total cost and spatial requirements, and offers the higher renewable contribution. In this paper, a novel configuration of an energy pile with a spiral coil was proposed. In order to investigate the effects of various factors on heat exchange performance of the pile spiral coil GHE, a numerical model of the pile with a spiral coil was developed. Based on the numerical solution of the model, the effects of pile diameter, pile depth, spiral coil group number and soil type on the heat exchange rate and soil temperature distribution of the spiral pile GHE were analyzed. The results indicated that increasing foundation pile diameter can improve the thermal storage capacity and thus enhance heat exchange rate of pile. But increase in foundation pile diameter can also result in the decrease of heat exchange rate per unit pipe length. So the pile diameter cannot be increased unlimitedly. At the same time, increasing the pile depth can improve the heat exchange rate of pile, and have little influence on heat exchange rate per unit pipe length. Thus the thermal performance of pile foundation can be improved by increasing pile depth. As for soil type, among clay, sand and sandstone, the sandstone was most conductive to the pile heat transfer and thus the soil temperature rise rate was minimum. On the contrary, the clay was the worst for heat transfer of pile foundation and soil temperature rise rate was the fastest among the three soil types. Additionally, increasing spiral pipe group number helped to improve heat exchange rate, but the heat exchange rate per unit length can be reduced largely. The experimental validation showed that the heat transfer rate and soil temperature predicted by the model were in good agreement with the corresponding experimental data, and the maximum relative errors were within 9.7% and 9.2% for heat transfer rate and soil temperature, respectively. [ABSTRACT FROM AUTHOR]