Numerical simulation study of the relation between water velocity and heat transfer in the deep geothermal well

The deep geothermal well is a new way to utilize geothermal energy,the distinctive characteristic of which is heat quantity exploited under earth without water pumped.In order to study the working state of the deep geothermal well,a model on the deep geothermal well with 4 000 meters depth was established.Based on the reasonable assumption,the heat transfer mathematical-physical model between geothermal well and stratum was established.The temperature gradient,lithology and transfusion of underground water were taken into account.A program was written and an analog computation was carried out.The model was tested and verified with an actual geothermal well,and the result shows: with the relative error between calculation temperature and actual temperature at 7.77%,the model is reliable.Moreover,the relationship between the velocity in the well and thermal power exploited,heat transfer radius were calculated and analyzed.The results showed that the largest thermal power exploited was 0.841MW,and the corresponding velocity in the well was 0.75m/s,the longest heat transfer radius at the 120th day 15.68m.