Thermal Dynamic Heat Transfer Characteristics And Thermal Insulation Optimization Of Directly Buried Ductile Iron Heat Pipe

With the increase of central heating area in China,the energy consumption of building heating in China has become a large part of the energy consumption in China's buildings.At present,the existing technology of steel welding heat pipe has some limitations.In this paper,a new type of heat pipe model with ductile iron pipe as base material and flexible socket connection is proposed.The simulation model was established by ANSYS software,and the in-depth study was carried out around the heat transfer characteristics of the pipeline and the optimization method of thermal insulation.First,The paper describes the heat transfer problem of ductile iron heat pipe,and establishes a set of scientific mathematical model through comparative analysis of mathematical model establishment methods.It can accurately describe the unsteady heat transfer process of double line ductile iron heat pipe directly buried in soil.Through the determination of calculation domain,control equation and boundary conditions,a more accurate new heat pipe model is established,which can improve the calculation and analysis accuracy of heat transfer characteristics,reduce the calculation workload,and provide a strong guarantee for the reasonable optimization design of insulation layer.Second,This paper describes the heat transfer problem of ductile iron thermal pipe,and establishes a scientific mathematical model by comparing and analyzing the mathematic model building methods.It is used to accurately describe the unsteady heat transfer process of dual-line ductile cast iron thermal pipe buried directly under the soil.Through the determination of the calculation domain,governing equation and boundary conditions,a relatively accurate new thermal pipeline model is established to improve the calculation and analysis accuracy of heat transfer characteristics and reduce the calculation workload,which provides a strong guarantee for the reasonable realization of the optimal design of thermal insulation layer.Third,The main task of this chapter is to use the ANSYS finite element software to establish the heat transfer simulation model,used to simulate the DN500,DN300 two specifications of ductile iron heat pipe in the main body,interface,elbow heat transfer characteristics.The simulation results were compared with the measured data,and the relative error calculation formula was used to verify the engineering accuracy of the model.The accuracy of the model is further illustrated.Finally,Through ANSYS software to establish a model for simulation analysis,the heat insulation optimization design of ductile iron heat pipe interface and elbow is carried out.At the interface,the heat affected area of the thermal bridge is determined,and the affected area is optimized.The prevention measures of the hot bridge at the interface of ductile iron heat pipe are put forward,which greatly reduces the heat affected area of the hot bridge.In the elbow part,the elbow part of ductile iron heat pipe is optimized and analyzed,and the light fabricated steel structure is put forward.The heat loss of elbow is greatly reduced.The economic thickness of thermal insulation layer of ductile iron thermal pipeline under the influence of thermal bridge is calculated.By comparing with the pipeline without thermal bridge,it is determined that the influence of thermal bridge can not be ignored.