Influence of heat storage on energy efficiency improvement of medium-deep coaxial borehole heating systems
Aiming at the long-term operation of the medium-deep coaxial borehole heating system which has issues of cold accumulation in rock-soil and decrease in the heat extraction capacity of the system,in this research,a numerical heat transfer model for MDGSHPs was established,the governing equations were discretized based on the finite difference method,and the accuracy of the model was verified with experimental data.This research separately studied the effects of heat storage temperature(Tin)and flow rate of hot water injection(G)on BHE heat extraction rate(Q),system energy consumption(W)and the coefficient of system performance(CSP)in the next heating period.The results show that the first step to realize heat storage is to determine the threshold value for the temperature of heat storage water.Below the threshold,heat storage will not be achieved,and the threshold temperature for this study is 50 ℃.After operating for 500 hours,when the inlet water temperature increases from 50 ℃ to 80 ℃,Q,W and CSP increase by 54.41 kW,8.96 kW and 0.17.Furthermore,when the flow rate of hot water injection increases from 1 kg/s to 7 kg/s,the growth rate of Q,W and CSP are 7.71％,6.34％and 1.19％.Therefore,a small flow rate with high temperature of heat storage water is recommended during the heat storage period which will improve heat storage effect and reduce energy consumption.This study provides a theoretical basis for heat storage in MDGSHPs.
万方数据
维普
