Development Of Underground Concrete Heat Storage Pile Experiment Table And Numerical Simulation On Temperature Field

Energy is one of the most serious problems which the world and Chinese soio-economic development facing. The shortage of fossil fuels and environment problem according, directly influent the implement process of sustainable development strategy of human society in the future. In recent years, every country is developing new energy. The solar energy has been paid extensively attention by people as a kind of environment-friendly and infinite natural energy source. The storage of solar energy has become a hot issue of domestic and international research. At present, there are three main methods of solar energy storage: sensible heat storage, latent heat storage and thermo-chemical heat storage. Foreign has adopted underground high and medina temperature energy storage methods such as underground artificial water tank (aquifer), underground natural soil (rock) and so on. Water and rock heat storage is currently in a highly developed stage.Under this condition, underground concrete heat storage pile is brought forward as new way to approach of using solar energy. It is necessary and timing. Using of underground concrete heat storage pile that as storage mediator of solar is a new idea and new method to explore the underground storage of solar. Jilin University is the only national school research in the heat storage technology of concrete and thermal storage models. Therefore, it is important to discuss the underground concrete heat storage pile is an importance subject project that have both the theoretical and practical value. For this purpose, analysis and experimental study of the heat transfer model about the vertical U-tube heat exchanger of underground concrete heat storage pile is carried out in this paper.This article based on a review of related research on storage energy of solar both home and abroad, and applying Jilin University Green Energy Development and Utilization Laboratory, development an experiment table of the underground concrete heat storage pile. There are 3 primary parts in this system: an underground heat storage pile, a source of heat water tank (is to simulation of solar collectors) and a data automatic collection and recording system. The experiment table has provided the experimental condition for research each aspect of underground concrete heat storage pile system.In this paper, researched on the concrete temperature field around the tube heat exchanger which could more intuitive reflect the heat storage effect of the underground concrete heat storage pile. This thesis utilizes founding concrete temperature field model around the vertical heat exchangers, and using the engineering compute software MATLAB to make numerical simulation on concrete pile temperature field. Through the numerical simulation of a detailed analysis of the different depth in pile, different concrete backfilling materials, different running time of the storage heat systems, different size tube diameter and variable heat flux condition bring impact on the concrete temperature field around the tube heat exchanger.The simulation results show that, in the short term (90 days) operating conditions, the concrete thermal conductivity directly affect the storage heat effect, while the concrete thermal conductivity are 1.28W ( m·℃)W and 1.7 ( m·℃) the temperature of concrete pile are different. The temperature of the concrete near the tube wall only 62.8℃when using materials which adding 3% graphite that has a large thermal conductivity, but, when using concrete materials without adding graphite as high as 71℃. However the temperature of pile's edge (radial distance 1.0m) in two different concrete materials is almost the same. showing that the good thermal conductivity properties of concrete backfilling materials to increase the temperature margin between the fluid and the surrounding concrete thereby increasing the heat exchange. For the long-term thermal simulation analysis of three months operating the thermal influencing radius reach the edge of concrete pile. The simulation results of the impact on concrete temperature field while3 L /min, 6 L /minand 9 L /min (418 W / m~2,836 W / m~2and 1254 W / m~2) three different heat flux density show that, when the greater of heat flux the temperature difference between the fluid and the surrounding concrete is the smallest. So is adverse to heat exchange between the underground tube and soil. Finally, summarizing the advantageous heat exchanger designed heat flux.