Numerical Simulation Research On Solar-ground Source Heat Pump System Used In Daqing Field

As important renewable energy,solar and geothermal energy have received widespread.In China,heating period lost a long time in cold areas,and most heating consumption was the primary energy.Therefore,the study of renewable energy in heating applications is of great significance.For Daqing covering a vast territory and thinly populated,fully laying the heating network was not conducive to energy conservation and environmental protection.Solar-ground source heat pump system is suitable in this area.The main works and the results of this paper are as follows:(1)The formula of collector and collector area in the solar energy system was introduced,and the formula of collector area was simplified by the test results of the test bed.The heat transfer principle of the buried heat exchanger and the heat storage characteristics of the soil were analyzed.(2)Based on the soil types and characteristics in Daqing area,a vertical U-tube three-dimensional heat exchanger model was established.Comparing the experimental data with the numerical simulation results,we could verify that the model was in line with the actual project.(3)For single U-tube heat exchanger with seepage,the influence of the inlet flow rate,inlet temperature,backfill material and pipe material on the heat transfer was simulated.The temperature of the outlet increasing with the increase of the flow rate,the PE pipe with the outer diameter of 32 mm,the flow rate could be chose in the range of 0.4m/s ~ 0.8m/ s.As the temperature of the inlet heat exchanger is gradually increasing,the temperature of its exports gradually increased,and the heat transfer curve increased linearly.Backfill of raw soil was used as much as possible.If the original soil backfill cost is high,thermal conductivity could be increased to improve heat transfer of backfill material.Similarly,buried pipe material with large thermal conductivity should be selected as much as possible.It is found that the outlet temperature of the seepage layer was relatively low than that without the seepage layer,and the seepage flow was helpful to improve the heat transfer efficiency of the heat exchanger.When seepage occurs in different soil layers,and the outlet temperature is different,and the outlet temperature is the lowest at the second level.(4)The influence of buried pipe spacing,heat storage temperature,heat storage time and pipe arrangement on the temperature field of underground soil was analyzed according to the change of soil temperature.Without heat storage,the greater the distance between the tube,(5)the smaller the effect of heat transfer wells,the more conducive to heat transfer.Under these conditions,the polygonal arrangement is better than the cross arrangement and order.Without heat storage continuous operation,the heat exchanger tube efficiency reduced,and heat storage conditions should be introduced.Under the condition of regenerative operation,it was found that the smaller the temperature of the buried pipe was,the faster the temperature was.During heat storage process,the cooling capacity of the polygon is collected and concentrated in the center of the polygon.The heat could not release to surroundings and beyond easily,so the efficiency of heat storage was far less than other ways.