Abstract:In this paper, heat transfer model of buried pipe heat exchanger system has been introduced. Heat transfer power and the duration of the buried pipe, the mode of operation of heat pump unit, the specification of the heat exchanger, the external backfill material and geological and hydrogeological conditions, the heat transfer of underground rock mass have been studied. It is regarded that the range of thermal conductivity in the surrounding rock masses is positively correlated with the level of heat exchanger power, the length of the duration of thermal conductivity, the material of the external backfill and the heat conduction performance of the surrounding rock masses. The intermittent operation of heat pump unit is beneficial to the timely restoration of geothermal field. Winter heating and summer cooling mode can weaken the thermal influence of single load aggregation. The thermal influence of the double U-type De32 buried pipe is larger than of the single U-type De25 buried pipe under the same energy condition. The seepage action of groundwater is conducive to weaken or eliminate the cumulative effect of heat which is caused by the disequilibrium of the absorption or desorption of heat of the buried pipe exchanger. With stronger seepage action of groundwater comes lager range of thermal impact. A simulated summer working condition tests that the 8w heat transfer power is continuously running under the same condition as other conditions in the clastic rock area of eastern Jinan. It is showed that with the center of heat transfer hole, the temperature response rate and influence amplitude of rock mass are negatively correlated with radial distance, the nearer the distance, the greater the response rate and the impact amplitude, the less the converse will be, the more the thermal impact range of the buried pipe heat exchanger is greater than 5m in 47days.
