The Study On Influence Of Ground Heat Double-U Exchanger Of GSHP Under Layered Geological Structure

Ground source heat pump system is a mature way of energy development in ourcountry at present. Because of its little pollution and high efficiency, it becomes the oneof the key development directions in energy adhibition,is a new solution risingresource.Research for ground source heat pump exchanger is mainly taken from theconstruction load, circulating water flow rate, initial temperature and the coupleddistribution of buried pipe heat exchanger in geotechnical engineering, however, groundsource heat pump technology has not entered a model perfect development inChina.Buried pipe heat exchanger is the foundation of the ground source heat pumpsystem. In the process of design, determination of physical parameters for soil in mosttimes is according to personal experience, local test or thermal response experimentsonly in a borehole,regards soil as homogeneous objects, get comprehensivegeotechnical coefficient of thermal conductivity, ignoring the vertical geological layers.By studying the soil source heat pump, and based on numerous literatures and the3D single pipe and field around pipe simulation put forward on by the predecessors, thissubject set up geological structures of3D simulation under different geologicalconditions and control the coefficient of thermal conductivity and the depth of soil forone-factor analysis.On the basis of actual engineering data, the paper establish the ground source heatpump single pipe model of vertical double U multilayer ground, simulates in software,analysis the numerical solution and test values, concludes that the ground source heatpump vertical double U multilayer ground single pipe model is in conformity with theactual dates of thermal response, is an objective and scientific physical model.Based on the vertical double U single pipe model, introducting the soil thermalconductivity λiand depth h in geotechnical to represent different geological conditions,with the average heat transfer coefficient as evaluation parameters, it searches for thechange of λiand h limit and looks for the evaluation standard of new geologicalconditions is similar to the template model geological, gets the various geologicallayers limit value of the coefficient of thermal conductivity absolutely disturbance underthe single pipe model.When the coefficient of thermal conductivity rate of disturbanceis within the scope of this limit value, the change of average heat transfer coefficientrate is not more than5%, it can be thought that in single pipe model the new geological conditions and geological template conditions are similar,they have similar linear meterof units in heat transfer performance at the same flow rate and heating conditions. It canbe evaluated for two kinds of geological structure similar to that of the lower coefficientof thermal conductivity of rock mass, which absolute rate limit about33%,16%and11%.Based on the vertical double U multilayer ground field around pipes model as theoriginal model, controlling its geological layer thermal conductivity λi, with the averageheat transfer coefficient as evaluation parameters,it analysis the heat transfer in depth,explores the change of the λilimits and the evaluation standard new geologicalconditions is similar to the geological template model in field around pipes model, getsthe various geological layers limit value of the coefficient of thermal conductivityabsolutely disturbance under the field around pipes model. When the coefficient ofthermal conductivity rate of disturbance is within the scope of this limit value, thechange of average heat transfer coefficient rate is not more than3%, it can be thoughtthat in field around pipes model the new geological conditions and geological templateconditions are similar,they have similar linear meter of units in heat transferperformance at the same flow rate and heating conditions. It can be evaluated for twokinds of geological structure similar to that of the lower coefficient of thermalconductivity of rock mass, which absolute rate limit about37%、19%、14%.Finally, it summarizes the cause and characteristics of the southwest karst geologyand influence on drilling construction of ground-source heat pump system. In view ofthe problems of karst area of drilling construction, it puts forward some effectivepractical engineering drilling construction technology.It compiles a software for thethermal response test analysis and calculation.It builds the geological conditions andsoil coefficient of thermal conductivity distribution in Guiyang region.Through the study of the subject it can get absolute perturbation rate limit ofthermal conductivity of on, middle and lower level under the vertical double Umultilayer ground on single pipe model, and provide evaluation standard of a newgeological condition is simila rto geological condition. According to the geologicalcondition evaluation standard reference template database,it can roughly estimate theheat transfer effect of the geological units and, can even save the thermal response testwhen geological layer is very similar, shortens the time limit for project, also provides anew reference for engineering design.It could get absolute perturbation rate limit ofthermal conductivity of on, middle and lower level under the vertical double U multilayer ground on field around pipe model, show the connection between the soilcoefficient of thermal conductivity and the heat transfer effect more clearly.It canprovide evaluation standard for the heat transfer effect of field around pipes underdifferent geological conditions and provide a reference for engineering design.