The Application Of Finite Element Method Of Lines In The Research Of Heat Exchanger Under Ground

The key of the design and application of the Ground-coupled heat pump is the theoretical research of the heat exchanger under the ground, which involve a lot of factors such as the style of pipe laying,the physical appearance of the ground, the research of heat conductmodel. It is the first to raise the circular cylinder heat conduct model which based on the Finite Element Method Of Lines.This method has the merits of cylindrical bore heat source theory and avoid the flaw of the utilization of infinite medol.The method is closer to the engineering conditions. Also,the calculation of the underground thermal field of with FEMOL axisymmetric element is been given.The FEMOL is the method whichi is given in 90ths,as a new structure analysis method,it has been used in solid mechanics maturely,but in the study of heat transfer, there is only the research of the two-dimensional steady-state temperature field.Finite Element Method Of Lines has been Combined with The analysis of thermal field which is under cylindrical-coordinate system is been given in this paper. First, the axisymmetric element is chosen as the unit in this paper, in which the radius orientation defined as base line and the vertical orientation derined as konode. Then,the paper analysis the functional equations of thermal field, arrive at the ordinary differential equations and corresponding boundary conditions by means of variation of the functional equations is been analysised and been bringed in the first second and third kind boundary condition.by the utilization of COLSYS which is a open source program ordinary differential equations solver,it is not difficult to obtain the corresponding distribution of temperature and the needed thermal field.Ground-coupled heat pump (GCHP) air conditioning systems utilize ground soil as a low-garage heat source,which achieve heat transfer between the ground and a working fluid circulating in a closed loop buried under the ground, and then provide heat and cold to buildings. GCHP increasing attention has been paid to GCHP at home and abroad thinks for its significant energy saving and environmental protection benefits. But the research of GCHP in China still in its initial period and has no mature design specifications or a summary of operating experience. So,it is meaningful to do reach on thermal field of heat exchanger.Functional of the axisymmetric element thermal field are calculated in the first,second and third boundary conditons,then the ordinary differential equations and corresponding boundary conditions are concluded. Then, the serviceable range, solving function and operation method of ordinary differential equations solver are introduced and its accuracy is authenticated. The accuracy of COLSYS completely satisfies request which showed in the result. At last, COLSYS is used in the paper to calculate the ODEs and its boundary conditions and then compare with the analytical solutions. The comparison shows that FEMOL can be applied to the ground thermal analysis and get high accuracy and a satisfactory answer.