A Design Method For Heat-exchanger Of Ground-source Heat Pump Based On Line Heat-source Theory And Step Heat-flux Theory

Ground-source heat pump technology is a important application form ofrenewable energy in building,and it will also come to be one of the most promisingair-conditioning techonology in the21st century.The scientific design of pipeheat-exchanger,which is the core part of ground-source heat pump,makes big sense torunning performance and economic performance of the system.The thesis makes analysis and comparision on the different heat transfer model inborehole,after which the infinite line heat-source theory and one-dimensionalheat-conduction model are considered to be the most commomly used methods to theheat transfer analysis.The acquisition of soil thermophysical parameters is thefundamental work of pipe heat-exchanger design.The thermal-response test methodbased on infinite line heat-source theory is commonly used to obtain soilthermophysical parameters in engineering.The combination of slope method andparameter-estimation method for data process of thermal-response test could lead toan accurate result.The infinite line heat-source theory is based on twopremises,namely constant heat flux and continuous running working condition,whichlimit the application of this theory.By introducing the idea of step heatflux,equivalence principle and superposition principle,a theory which fits intovariable heat flux and intermittent running working condition is created.This theoryoffers the expression to calculate the temperature response of circulating fluid at thetime heat-exchanger ends its running work in the whole season of air-conditioning.Bydealing with,as well as making use of the data of thermal response test hold byauthor,this thesis successfully verifies the correctness of the theory of variable heatflux-line heat source,which is recommended to the designing for pipe heatexchanger’s length of ground-source heat pump.According to the temperature reponse of circulating fluid,as well as a maximumlimitation in cooling season or a minimum in heating season,a design method forheat-exchanger of ground-source heat pump is introduced.This design method,whichis based on the theory of variable heat flux-line heat source,could be used to calculatethe length of heat-exchanger both in cooling season and heating season ofair-conditioning.A computing program,which is helpful to analyze the influence thatdifferent running time,air-conditioning season period and limitation value of circulating fluid have on the design-length of heat-exchanger,is writed to providereference for engineering.