The Application Of Finite Element Method Of Lines In The Research Of Ground-Coupled Heat Pump Under Ground Heat Exchanger Within Transient Thermal Field

Finite Element Method of Lines is a semi analytical method which is raised in the beginning of nineties of last century, a lot of experts and scholars do a fruitful work in the research of applicating the Finite Element Method Of Lines in the domain of solid mechanics. In recent years, a lot of research work which is mainly about trying to apply the Finite Element Method of Lines in thermal field analisys has been done by our research team, and made a series achievement, developed the program of plane element and axial symmetry element for thermal field analisys with Finite Element Method of Lines.Based on the achievement of precursor, I try to extend the serviceable range of Finite Element Method of Lines in transient thermal field analisys.In other words, the ground work of this paper is to achieve reansient thermal field analisys with Finite Element Method of Lines. In this paper, I start with the most typical heat conduct problem which without internal heat source. The temperature of the field is not only decide by the position but also by the time point, which is the definition of transient thermal field.Using Finite Element Method of Lines smash the area in semidiscretization with plane or axial symmetry element which is develop by the postgraduate last session; Using receding difference to disperse the time. Although there are some more precisely method such as C-N method, Galerkin method, but receding difference is unconditional steady and without surge nomatter how big the time step is, as the first time to get into transient thermal field with FEMOL, is a quite suitably choice.The program of this paper is compiled in Fortran. It can run in any computer with any edition of Fortran compiler. To make sure the user can input and write the necessary datas as convenient as they can, the program using txt files to input and write most of the datas. Using modules to declare the variations and subroutines to realize most of the function, this can make the program clearer in its structure. With the explanation sentence, the program is more readable. Using variable size array instead fixed array can save EMS memory and acceleration the calculate speed. COLSYS has been choosed to be a ordinary differential equation solver in the program. It inherit and develop the achievement of the predecessors, so the program can solve the steady and transient thermal field.The user can put out the temperature of any any position at any time. Last, the program write the process datas in a txt file in case the user need to check on the calculate process.The design of under ground heat exchanger of the Ground-coupled heat pump mainly include the distance, depth and number of the tube well. Before this, we must calculate the heat energy exchange from the exchanger, which involve a lot of factors such as the style of pipe laying, the physical appearance of the ground, the research of heat conductmodel. The method of Finite Element Method Of Lines has been used to analyse the thermal field of the soil around the tube well., choosing receding difference as time differencing method, simulate the transient thermal field around the tube well, so the designer can refer the result.