Analysis And Application Of Underground Heat Transfer In Vertical And Horizontal Hybrid Underground Heat Pump Heating System

The traditional vertical buried pipe ground source heat pump system has the problem that the heat extraction from the buried tube side is greater than the heat storage during the operation in the northern area where heating is the main supplementary cooling.Long-term operation will cause the deep soil temperature to decrease year by year,which will seriously affect the stability and operating efficiency of the system.This problem restricts the application of ground source heat pump technology in northern villages and towns.In response to this problem,this paper proposes a vertical and horizontal hybrid buried ground source heat pump system,and conducts underground heat transfer analysis and application research on the system to solve the problem of unbalanced underground heating and cooling load,and expand the ground source heat pump system in northern villages and towns Range of application.Using TRNSYS transient system simulation program as a platform,a hybrid buried ground source heat pump system model for residential buildings in a village and town in Jinan was established.The analysis results show that:comprehensively considering the three factors of heat recharge in the transition season,heating capacity in winter,and economy,the buried depth of the horizontal buried pipe in the hybrid buried pipe system in Jinan should be about 1.1 m.The effects of six different buried depths on horizontal buried pipe heat exchangers were simulated and analyzed.The calculation results show that the recharge heat and system COP_HGG of the horizontal buried pipe along with the increase of the buried depth in the spring and autumn transition season is continually declining;in winter,the heat transfer capacity of horizontal buried pipe increases continuously with the increase of buried depth.Under the research conditions,when the buried depth exceeds 1.1 m,the growth rate of the heat transfer capacity of the horizontal buried pipe slowed down;the engineering cost of the horizontal buried pipe also increases with the increase of the buried depth.When the buried depth exceeds 1.2m,the cost is greatly increased.The established system model was used to simulate and analyze the heat recovery by the vertical buried pipe in summer and the effects of different ratios of vertical and horizontal hybrid buried pipe.The results show that the heat directly supplied by the vertical buried pipes in summer accounts for about 60%of the total heat required,and the horizontal buried pipes are needed for heat recharge;the ratio of horizontal and vertical buried pipes?M?is about 45%.The calculation results show that with the increase of the horizontal buried pipe ratio M,the heat and system COP value of the transition season increase with the increase.When M is about 45%,the buried pipe system basically reaches the basic balance of heat.When continuing to increase M,the effect of increasing the COP value is not obvious,while the increase in initial investment increases.On the basis of building load simulation,based on the system parameters such as the buried depth of the horizontal buried pipe and the ratio M determined by the study,the recuperation heat and system COP were simulated and analyzed.The results show that:the vertical and horizontal hybrid buried ground source heat pump system,the proportion of supplementary heat increases,and the underground cold heat tends to balance.The energy efficiency ratio of the system is significantly improved.The calculation results show that:he heat recovery accountes for 90.1%of the total heat required in transition season and summer,the average annual soil temperature drop is about 0.6%,and the imbalance rate of underground heating and cooling load is about 2.9%;The average system COP in late spring,summer,and early autumn are 5.8,12.2,and 8.5 respectively,and the integrated annual system average COP is about 7.1.The results of the study indicate that the hybrid buried pipe heat pump system has a good heat recharging effect and a significant energy saving effect.Compared with the solar collector heating method,both are technically feasible,but the former is obviously economically superior.Based on a ten-year life cycle simulation calculation,the annual cost of solar collector replenishment is 3.5 times that of horizontal buried pipe replenishment.The vertical and horizontal hybrid buried ground source heat pump system has obvious economic and technological advantages.The research results will effectively promote the application of buried pipe ground source heat pumps in residential buildings in northern villages and towns.