Temperature Field Heat Exchanger Pile Tests And Research Of THM Coupling Theories

Along with science's and technology's rapid development, society's unceasing progress, the energy question became now a society's major issue already. People are unceasingly developing new energy alleviates. The heat pump which takes one kind through the consumption few high grade energy and rose the quantity of heat from the low temperature level to the high temperature level special installment has received people's favor. And the ground source heat pump also by its characteristics of environmental protection, the energy conservation, the movement reliable and so on obtained the widespread application in overseas. Along with the energy structure's continual readjustment, the public environmental consciousness's unceasing enhancement, this technology will certainly to have a bigger development.In the ground source heat pump's family, the heat exchanger pile installation belongs to the new technology. Through install each kind of tubular exchanger installment underground ,it keep off the earth supports and protections, ground reinforcement and transform the shallow layer low temperature geothermal energy.It has the pile foundation and the ground source heat pump function together in advance. This also saves the drill hole working procedure, saves the operating charges and use building ledger wall's area effective. This kind of technology's promotion will be provides the new application space for the small green space area, the volume fraction high building and very suits our country's national condition. It will certainly to become the new application direction.The heat exchanger pile model is based on the Fourier heat conduction law in the early time which had not considered that the flowing of ground water and the convection and the machinery disseminate the function, moreover, because all theories are the drill hole bury the heat interchanger, also had never considered the heat interchanger's temperature stress field and the bias field. Generally only uses the simple compound unstable state heat conduction which neglect mechanics field, using a thermal conductivity added value describes in the ground caloric coupling method the moisture content and the air transport process function are bound to bring the big error obviously which the corresponding result will be lead heat interchanger's size to be big and will affect the normal operation of project. And domestic and foreign started some related THM coupling research in the 1990s is applies in petroleum natural gas development and nuclear waste storage and so on. Their fundamental research was the crevasse rock mass coupling question and had does not have THM coupling research of ground place source heat pump underground system particularly the heat exchanger pile.Based on above this article under the support of the natural fund "Heat Transform Pile– Hydro-Soil system's THM Coupling effect Mechanism Research" (No.40472134) did theory and the experimental study the mechanics and heat conduction character of this kind of new heat-exchanger pile under heat flow solid coupling theory .In this experiment it did not consider that limits side. It carried on the vertical load determination to the different tube type in pile and analyzed the influence of heat-exchanger rig to the pile intensity. Joined the U tube and the spiral pipes to manufacture seven piles, for normal reinforced concrete simulation pile (did not increase any tube) to take the contrast to be tender, two join a U tube, two join three U tubes and two join a spiral pipe. It had analyzed to the experimental result, obtained the relations of the theory supporting capacity and the actual supporting capacity with respect to the U tube quantity.With summarize the theory of predecessor's heat transfer model, it has conducted the preliminary study based on the V.C.Mei heat transfer model to the heat exchanger pile. This model was builded on conservation of energy's foundation and constituted by the system energy balance conbined with heat conductivity equation. It was obtained through a series of suppositions and was assigned boundary condition in each contact face.It was discussed the TH coupling theoretical model which had considered the ground water influence, established the the numerical model of heat exchanger pile installation underground temperature field and analyzed law of development to temperature field under the different ground water speed of flow law of development to temperature field. Through the massive hydro-thermal coupling research, the proportion relationship between temperature field and time was found. It also has contrasted the temperature change rule of different observation point and obtained the temperature proportional relationship under the different ground water flow speed.It was established the THM three coupling mathematical models from the distortion field, the equation of continuity and in the energy- conservation equation in the foundation of several front chapter of experiments and theories. Then the model was used to simulated a heat exchanger pile engineering test which did in Sweden Lausanne by Lyesse Laloui et al. Model serviceability will be established by contrast of simulate and the experimental value. A large number of iterations of numerical simulation work was done by change the model's parameter condition and did some classified contrast and analysis. The contrastive analysis was also done to the stress causes by heat transfer and by the building load. It was also analyzed the stress strain of the pile and surround soil as well as the temperature field development rule considers the THM coupling.This paper's research will rationalize the type, quantity design of heat transfer tube in pile and quantity design more rationalize and provide rationale and technology for the heat transfer model, the hydro- thermal coupling, the thermal- mechanic coupling as well as the THM coupling and the parameter about the heat exchanger pile.