Numerical Study On Heat Transfer Of Double U Type Buried Well Group

To determine the heat transfer ability of the vertical buried tube heat exchanger is the key work of the whole design of the ground source heat pump system, it is also related to long-term efficient operation of ground source heat pump system. At present, most studies are limited to single well heat exchanger, on the contrary, little relevant research is done about the large well group of heat exchangers. Because, compared with the single well heat exchanger, the existence of heat interference between wells in the well group brings the very different to the heat transfer regularity of each well and increases the difficulty of research. Moreover, most researches on the well group need to get strong theoretical foundation and complicated calculation process, therefore, these studies are difficult to directly used for engineering; In addition, in the project, the heat transfer model based on soil is pure heat conduction model in most of the software for the design of buried tube heat exchanger, ignoring the influence of groundwater seepage to soil heat transfer and the results still need to be revised. Therefore, the research and development of a set of design method, considering the influence of the heat interference between wells and groundwater seepage to soil heat transfer and suitable for engineering application of buried tube heat exchangers, is particularly important.Firstly, the three-dimensional unsteady model of single well and typical well group heat exchanger is established by the Fluent6.3software, and on the basis, the model of single well heat exchanger is verified whether there are circumstances of the groundwater seepage and the validation results show that the model is reliable. Secondly, the square well group is identified as the object of study through the analysis of well fluid inlet-outlet temperature difference with the variation of running time in the typical well group. Meanwhile, the coner well, aris well and core well are defined in the well group. At the end, the concept of heat equivalent value and the calculation method of the quantity of well heat exchangers through the heat equivalent value and the quantity of heat exchange in a single well are put forward.The paper focuses on the influence of various factors, soil thermal diffusivity, initial soil temperature, soil thermal conductivity, temperature and velocity of the fluid at the import, variants in well spacing, operation modes and the groundwater flow on the heat equivalent value of each well in well group in the absence of groundwater flow; as well as, the simplified model of the heat transfer quantity of well group is put forward through using the concept of the heat equivalent value, moreover, the simplified model is verified by the result of simulation of stratified soil seepage and the result show that the two relative error is2.2%and the simplified model is reliable.