The Study On Influence Of Ground Heat Exchanger Along With Different Geological Structure

The soil source heat pump is currently a comparatively mature and advanced formof energy utilization in our country. As it produces little pollutant and could effectivelyutilize geothermal energy, it has become the key development direction of energyutilization in china. A lot of researches have been done about building load, fluidvelocity, rock and geotechnical initial temperature and the layout of buried pipe heatexchanger for the ground heat exchanger in our country, but the ground source heatpump does not enter the perfect development pattern. On the other hand, our countrylacks of detailed geological structure analysis of regional geology that the groundsource heat pump in many areas designed merely depends on personal experience andpartial test to determine physical property parameters of the geotechnical. Besides,only the physical parameters of geological uniform are taken into consideration for thedesign of ground source heat pump, while the analysis of layered structure ofnonuniformity in geological is ignored.By studying the soil source heat pump, and based on numerous literatures and the3D simulation put forward on by the predecessors, this subject set up two differentgeological structures of3D simulation, one is the uniformsingle physical geologicalstructure model,, another is the non-uniformdual physicalgeological structure model.According to the need of modeling, the type of geological is defined to provide the basisfor dual physical geologic structure model of different geological analysis. According tothe need of numeric analysis，the type of geotechnical parameters is defined to providethe basis for the analysis of the physical properties of different geotechnical fornon-uniform dual layers and different geological structure model. Besides, according tothe need of numerical analysis, the concept of average heat transfer coefficient isdefined, and the average heat transfer coefficient is used as evaluation parameters toestimate the performance of heat exchanger.For the uniform single physical geological structure model, the influence ofdifferent geological properties for different physical properties, power of heating power,fluid velocity and initial average temperatures of rock on the performance parameters ofheat exchanger are mainly analyzed. The result of the analysis indicates that thedifferent heating power, fluid velocity and geotechnical initial average temperature insingle physical geological structure have no effect on the average heat transfer coefficient of the heat exchanger. According to the different patterns of soil parameterscorresponding to the change of the average heat transfer coefficient under the fixedworking condition, the conclusion that the greater the coefficient of thermalconductivity of the geotechnical parameter type is, the greater the average heat transfercoefficient is. And fitting the associated type is conducted.For thenon-uniform dual layers and different geological structure model, analysisconsists of two parts. On the one hand, the influences of different geological propertiesfor different physical properties, power of heating power, fluid velocity and initialaverage temperatures of rock on the performance parameters of heat exchanger areanalyzed and experiment was conducted to examine the change of heating power andmedium velocity exerts no influence on the average heat transfer coefficient,contrastingwith the uniform single physical geological structure,and put forword the concept ofequivalent coefficient of thermal conductivity. On the other hand, according to the typeof geology and soil parameters that have been defined, the influence of geological typeon the heat transfer performance parameters of heat exchanger in six types ofgeotechnical parameters is separately studied. Besides, the influence of physicalproperties of two kinds of geotechnical on the heat transfer performance parameters ofheat exchanger under the same geological type is studied. Finally, according to therelations of the average heat transfer coefficient K and the depth of sublayergeotechnical h, and the heat conductivity coefficient of higher geotechnicalλ and theheat conductivity coefficient of sublayergeotechnicalλ, and fitting equation.Through the study of the subject, not only we can get the reasonable significanceabout the evaluation of buried pipe heat transfer performance using the average heattransfer coefficient, but find the relationship between the average heat transfercoefficient and soil coefficient of thermal conductivity, its the influence parameters,aswell. At the same time, the influence factors which fact the average heat transfercoefficient of non-uniformity of conditions are the thermal conductivity of verticaldifferent geological structure and the depth of seam division. In terms of evaluating ofcomplex heat transfer performance of buried pipes under the ground and making up forthe deficiency of the thermal response test,it has a certain reference value.