| Energy saving and environmental protection has increasingly become the mainstream trend of social development, and the ground source heat pump is a new technology of heating and air conditioning on saving energy and reducing air pollution and carbon emissions effectively.In the 21 st century, ground source heat pump has been widely developed in a rapid speed in our country, but this technology has encountered many problems in the process of speed development.The thermal imbalance of soil is one of the very important question.This paper chose two buildings of a university in Zunyi as research objects,two air conditioning systems of the buildings alternate use a common ground source heat pump system, the ground source heat pump system was used by the teaching building during the day, and night for the use of student apartment.Then analyzed the soil thermal equilibrium problems of the ground source heat pump system under the long-term running by using a software named TRNSYS.This paper researched the characteristics of soil temperature at first, determined the thermal physical property parameters of the soil through the constant heat flux thermal response test, then analyzed the distribution of soil temperature and the law of its temperature variation by combining with the calculation formula of the soil temperature distribution,the value of calculated was coincide with the experimental value.Then build the model of energy consumption calculation,analyzed the annual dynamic load of the teaching building,the student apartment and the annual dynamic load when the air conditioning system of the two buildings operated alternatively, the cooling load under dominant in both three models.Using TRNSYS to simulate the ground source heat pump system while the system running for a long time, analyzed the average temperature of the buried district, the inlet/outlet temperature of source side,the inlet/outlet temperature of load side and the change of COP. The results show that this system exists a obvious heat imbalance,the average temperature of district soil rise 9.34 ℃ while a 10 years operation, its what we can not accept;the inlet/outlet temperature of source side has a trend of rising;the COP lowering in the summer but increasing in winter.Analyzed the model of the teaching building and student apartment respectively while their air conditioning systems operated independently, the result shows that both systems exist thermal imbalance.Compared with the former model, even the balance of heat is superior when two buildings operated alternatively to the teaching building system, but because of it has the longest running time every week,the soil temperature rise is the largest after 10 years operation.Therefore, the operating time(daily/weekly) has a great influence on the change of the temperature underground.We can not only according to the annual heat balance but also consider the influence of the running time in engineering.Finally analyzed the factors which has a influence on the heat balance of ground source heat pump, the space of buried tube well had significant effect on thermal imbalance, buried depth, buried pipe diameter also have effect on the change of soil temperature.Put forward some suggestions on this project combined with the analysis of influence factors on thermal imbalance problems. The author advise this system and the eligible projects using alternate operation ground source heat pump air conditioning system + hot water system. The temperature of soil increased by 1.15 ℃,COPC reduced about 2.5%, COPH increased by 1%while the system run for 10 years after considering the hot water load. They changed in a acceptable range, therefore, this scheme is feasible.After adding hot water system will not cause investment increased significantly, the school running cost will reduce a lot. Recommended alternate operation ground source heat pump system + cooling tower system, this system also can completely eliminate the thermal imbalance of soil and reduce the initial investment. |
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