Research On Development And Heat Transfer Performance Of High Performance Ground Source Heat Pump Grouting Materials

Ground source heat pump grouting materials filled with soil medium as the ground heat exchanger,the stand or fall of its performance not only determines the stability of the buried pipe bundle installation,eventually will affect the heat transfer process of buried pipe system is running.Therefore,it is important to improve the performance of the source heat pump by using the appropriate additives to improve the comprehensive performance of the grouting materials of the ground source heat pump.The effect of taking scrap steel and graphite as additives compound on the comprehensive performance of grouting materials is analyzed through fluidity test,thermal conductivity test,compressive strength test and the use of comprehensive scoring method.The results show that adding scrap steel can improve the construction performance of the grouting materials with the maximum fluidity increase of 81.9% but adding graphite has little influence on construction performance.Moreover,scrap steel will lead to lower heat transfer performance of grouting materials,but adding graphite can make up 6.5% of the loss of thermal conductivity maximally.Adding graphite has a little influence on mechanical properties of grouting materials,but adding scrap steel can improve 97.5% of the mechanical properties.Through the results of integrated score method,it is found that replacing the rate of slag replacement slag by 40%,and continuing to increase the rate of graphite instead of cement,may be able to get better overall performance of grouting materials.In addition,according to the actual situation of engineering application,through to the grouting materials density,thermal conductivity,specific heat and thermal diffusion coefficient test parameters,such as,continue to further study the different curing temperature on the thermal physical parameters of high-performance grouting materials impact analysis.The results showed that the curing temperature increased to improve the integrity of the ground source heat pump grouting materials surface,and with the increase of curing temperature,thermal physical property parameters of grouting materials also rise,after dry grouting materials thermal physical property parameters of variations of small,more close to the saturated state values.In curing temperature 30 ? and graphite replace cement rate is 22% of the experimental conditions,the surface of the grouting materials minimum pore size and quantity,forming the results of the optimal;At the same time,increased from 5 ? to 30 ?,in the process of saturation and dry maximum thermal conductivity increased by 14.58% and 37.49% respectively,saturated with dry heat capacity maximum rose by 2.52% and 3.34% respectively,saturated and dry thermal diffusion coefficient of maximum rose 11.79% and 36.23%,respectively.6 groups on the basis of experiment,this article selects the corresponding grouting materials coefficient of thermal conductivity calculation theory model,compared with the test results analysis,through the error analysis,be suitable for this test under the condition of grouting materials coefficient of thermal conductivity theoretical model.Comparison results show that the curing temperature 5 ?,10 ?,15 ?,20 ?,25 ? and 30 ?,and-series model and Maxwell model calculation value and saturation condition of grouting materials coefficient of thermal conductivity test values alignment is higher,the two groups of model calculation value and experimental value of relative error within 4% and 5% respectively;In addition,the test value of the hasselman-johnson model with the thermal resistance of the interface was basically consistent with the test value of the thermal conductivity of the grouting materials in the drying state,and the relative error control was within 9%.