In order to fully consider the geothermal gradient and improve the calculation efficiency of the model, the heat transfer analytical model of closed U-shaped well heat exchanger is established by piecewise method, and the coupled calculation of the model is realized by programming. The accuracy of the model was verified by using the actual operation data of the system. Based on the model, the influences of the two operating parameters, inlet temperature and circulating flow, on the heat recovery of geothermal wells are analyzed. The results show that, compared with the measured data of optical fiber sensor, the average relative error of the model is 7.3%, and the accuracy of the model can meet the engineering requirements. On the premise of ensuring the basic load requirements, the geothermal well inlet temperature is between 5 ℃ and 16 ℃, and the circulating flow rate is above 80 m3/h, which can ensure the geothermal well in the efficient operation interval. In this operating range, the better thermal economy can be obtained by lowering the inlet temperature than by increasing the circulating flow, and the reasonable matching regulation of inlet temperature and circulating flow can increase the heating capacity of geothermal wells by 10%.
Key words
geothermal well /
heat transfer analytical /
operation optimization /
inlet temperature /
circulating flow /
heat exchanger
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