Research On Operational Characteristics Of Hybrid Ground Source Heat Pump With The Auxiliary Cooling Tower

Ground source heat pump system is a kind of energy-saving and environmental protection technology, which can be used for heat supply and refrigeration by using the characteristics of the huge amount of heat and cold capacity of the soil. As the world energy crisis and environmental pollution problems are becoming more and more serious, the technology is gaining more attention and application. However, for cooling dominated area, the problem of soil thermal imbalance and high initial investment in the application has become a key factor to the development of the system. In this paper, a hybrid ground source heat pump system with auxiliary cooling tower is proposed, which can effectively alleviate the thermal imbalance of soil and reduce the investment of buried pipe, so it has broad application prospects. Based on TRNSYS simulation and experimental study, the operating characteristics of the hybrid ground source heat pump system with auxiliary cooling tower was analyzed and studied in this paper.In the aspect of theory, based on TRNSYS transient simulation platform, a model of the hybrid ground source heat pump system with auxiliary cooling tower was constructed, the 15 years’ operation of the system was simulated and calculated dynamically in different typical climate regions and under different conditions, and the operating parameters such as the average soil temperature, the unit’s coefficient of performance, the inlet and outlet water temperature of buried pipes and the cooling tower’s heat dissipation rate in different heat dissipation mode were analyzed. The results showed that: in Shanghai, Chengdu, as the representative city of the hot summer and cold winter area, the hybrid ground source heat pump system with auxiliary cooling tower can keep the heat balance of the soil better, however, the adaptability of the composite system is poor in Guangzhou area with large difference in cold and heat load, after long-term operation, the temperature rise of the soil has not been significantly improved; in different operating conditions,the average temperature of the soil rises to a minimum in the continuous operation of the cooling tower, and the longer the auxiliary cooling tower operates, the more slowly the soil temperature rises; when cooling tower operates Intermittently, the coefficient of performance of the unit when the ratio of run time to down time is 1:1 is higher than that when the ratio of run time to down time is 1:2.In the aspect of experiment, by using multifunctional ground source heat pump laboratory platform, the experiment of separate operation of buried pipes to dissipate, cooling tower and buried pipes joint operation to dissipate, and cooling tower and buried pipes alternate operation between day and night to dissipate were constructed. The relationship between the change of soil temperature and the heat dissipating capacity of the parts of the system was analyzed and compared. The effects of different weather conditions and the operating time of the cooling tower on the heat dissipation of the system and soil temperature recovery rate were discussed. The results of the experiments show that:compared with separate operation of buried pipes to dissipate heat, the operation of cooling tower assisting buried pipes to dissipate heat can effectively improve soil temperature; the auxiliary cooling effect of the cooling tower and the recovery of the soil temperature in the sunny condition are better than the rainy weather conditions; the auxiliary heat dissipation rate of the intermittent operation of the cooling tower is smaller than that of the continuous operation, and the smaller the interval of intermittent operation, the greater the amount of auxiliary heat dissipation capacity; cooling tower and buried pipes alternate operation between day and night to dissipate can effectively help the soil temperature in the post restoration, the longer the cooling tower operates at night, the higher the soil temperature recovery rate is.The aim of the paper is to investigate operational characteristics of hybrid ground source heat pump with the auxiliary cooling tower, and provide theoretical guidance and technical support for promotion and application of them in the actual project.