Application Analysis Of Underground Water Source Heat Pump In Zhangye Area

Energy saving and emission reduction is one of the most important social problems in the world,and high efficient clean energy is the key link in building heating.Using the reverse cannot cycle,the underground water source heat pump system extracts heat from the shallow and constant temperature ground water to meet the needs of building heating.It has many advantages,such as high efficiency,remarkable environmental benefits and so on.It has a very broad application prospect.While the rational setting of the water well and recharge well is the key to the continuous and efficient operation of the underground water source heat pump system.Because the temperature of the recharge water in the recharge well is lower than the initial temperature of the underground aquifer in the heating season,it will inevitably lead to the slow decrease of the soil temperature around the recharge well.If the setting of the well and recharge well is not reasonable,it will cause the waste of land resources,or cause the temperature of the well water to decrease obviously with the running time,and the phenomenon of heat breakthrough will occur,which will restrict the efficient operation of the heat pump.The setting of the well and recharge well includes the number and proportioning of the well,the diameter and depth of the well,the spacing between wells,etc.,which involves many factors,such as soil porosity,moisture content and water diffusivity.The research and application of underground water source heat pump technology in recent years can be seen.On the one hand,the long-term continuous monitoring and analysis results of the actual project are still lacking,especially in the Zhangye area.On the other hand,the structural characteristics of underground well group is a necessary prerequisite for the continuous and efficient operation of groundwater source heat pump system,but the validation of its numerical calculation models and methods need to be further verified.Firstly,the long-term continuous monitoring of an underground water source heat pump heat source system in Zhangye area has been carried out in this paper.On the basis of the analysis of its performance and applicability,it is concluded that it is more reasonable and reliable and economic and effective.Secondly,the physical modeling is carried out for the research object,and the numerical calculation and analysis are carried out by using gambit and fluent software.The conclusions and reliable and effective conclusions of numerical models and methods used in the project are obtained,as well as the structural types and thermal characteristics of underground wells,including the relationship between parameters such as spacing and radius of well and recharge well and the underground temperature field.The study and conclusion can be used as a reference for the engineering application of underground water source heat pump system.(1)No matter from the aspects of economic benefits,social benefits,and user units’ controllability of heat source operation and management,the heating schemes of GSHP can be regarded as a preferred plan,which is in line with the current national policy.(2)The COP value of the heat source system,the heat pump large unit and the heat pump unit is reasonable during the test period of the underground water source heat pump unit.This shows that the performance of the underground water source heat pump unit is stable,economical and effective.Although it is always running for a set of units,testing the temperature of the user can meet the design requirements.It also shows that the heat source scheme and its design are more reasonable.(3)Although the greater the distance between the wells and recharge wells of the groundwater source heat pump system is,the longer the time of thermal breakthrough is,the more slight the degree is.However,considering the site restrictions of actual projects,we should minimize the area occupied by wells.Under the condition of the target model of zhangye area,the optimal spacing of the underground water source heat pump and recharge well is about 50 m.(4)The well radius has little impact on the stable operation of the heat pump system.In actual engineering,the most suitable well radius is determined according to the technical specifications of the pipe well and the survey data,which is about 0.3m~0.5m.(5)In order to ensure the normal operation of the groundwater source heat pump system,we should pay attention to maintaining the wells regularly,so as to avoid long-term use and cause difficulties such as water well blockage and recharge.