Application Of Ground Source Heat Pump System In The Bottom Of A Project In Tianjin

Ground source heat pump system has been widely developed and used at home and abroad because its energy-saving environmental advantages.Although vertical buried pipe system of ground source heat pump needs smaller occupied area compared with horizontal buried pipe system,it still needs extra area.Some buildings do not have extra area for drilling holes because of its high plot ratio and need to bury pipe system in the foundation of building or bury pipe system under the floor of building.The project discussed in this paper locates in Tianjin and is used for office.There is no extra area for drilling hole in this project because the basement of the sideline is close to the building line.So the underfloor pipe buried ground source heat pump system is applied as the cooling and heating source of the project.The eQUEST software is used to establish the building model in order to calculate the cooling and heating load yearly of the building.The unbalance rate of soil heat absorption and release every year was 9.12% based on the calculation of annual heat absorption and release.What was more,after the thermal response test of the ground source heat pump for 20 years running period,the soil temperature raised from 16.40? to 22.45? and the unit performance coefficient at cooling condition decreased 1.38 and the unit performance coefficient at heating condition raised 0.12.Since the heat exchanger buried under floor of the building,the operating surface of drilling hole located in the foundation pit.Take the convenience of operation and the saving cost into account,the project want to reduce the depth of the buried-pipes from 120 meters to 100 meters and reduce the well space from 4.2 meters to 3.5 meters.But the TRNSYS simulation result indicates that neither of the two plans was feasible,because both of them have great influence on the soil temperature and the unit performance coefficient.However,in order to avoid the upwelling phenomenon,it was practical to change the backfill material to medium sand because it has little influence on both the soil temperature and the unit performance coefficient after analyzing the TRNSYS simulation result.In view of particularity of the underfloor pipe buried ground source heat pump system,this paper analyzed the problems in the process of drilling hole under floor of the building and proposed some solutions for reference.In addition,this paper also discussed the economic advantages of the ground source heat pump system by comparing four kinds of cold and heat source scheme.