Research On Heat Transfer Law Of Horizontal Section Of U-shaped Geothermal Well In Caotan District Of Xi'an

Geothermal energy has attracted people's attention as a new renewable energy source.Using U-shaped geothermal wells to heat buildings is an efficient way of using geothermal energy.As long as the heating requirements are met,a reasonable design of the wellbore structure and the drilling length of the horizontal section can achieve the highest energy utilization rate.This paper takes the U-shaped geothermal well heating system in Caotan District,Xi'an,Shaanxi Province as the research object,develops a test platform for the heat transfer process of the horizontal well section of the U-shaped geothermal well,and establishes the heat transfer model of the horizontal well section of the U-shaped geothermal well through ANSYS FLUENT finite element software Carry out numerical simulation.It also summarizes the changes in the outlet temperature of the horizontal well section,the amount of heat taken,and the recovery of the ground temperature during non-heating under different water injection flow rates,borehole diameters,and lengths of the horizontal well sections.Under the same water injection flow condition in the horizontal section of U-shaped geothermal well,with the extension of heat transfer time,the outlet water temperature of the horizontal section gradually drops and at the same time,the outlet temperature of low flow rate is higher than that of high flow rate.With the increase of water injection flow in the horizontal well section,the exit water temperature decreases with the extension of heat transfer time,and the heat intake in the horizontal well section of U-shaped geothermal well increases.The longer the horizontal well section of the U-shaped geothermal well,the higher theoutlet temperature,and the higher the total heat extraction of the horizontal well section during heating.The outlet temperature of the horizontal section of the U-shaped geothermal well has a negative correlation with the diameter of the wellbore,and has a positive correlation with the total heat extraction of the horizontal section during the heating period.During the heating process of horizontal section of U-shaped geothermal well,the formation temperature gradually decreases.During the heating,the recovery of formation temperature after first fast and slow change trend,comprehensive consideration and geothermal heat recovery,in order to make U geothermal well horizontal section in a heating period is able to run normally,according to actual engineering situation and grass land construction geothermal well considering the project within the wellbore flow in the horizontal interval of the optimal flow rate should be 0.3 m/s,the formation temperature 81.8 ?,the most close to the formation of the initial temperature of 82?.