The Study On The Operating Characteristics Of The Soil Source Heat Pump System In Jiangsu Region

With the increasing growth of international energy issues, building energy saving has become a big trend in the field of international architecture to realise sustainable development, as well as an important task of China’s economic society. As a new renewable air conditioning system, the soil-source heat pump has the features of high energy efficiency, wide applicability, good stability and low operating cost. Currently, the theoretical researches and design applications of soil-source heat pump system are very mature, however, the operation management of the practical engineering is still defective. How to improve the efficiency of the system operation, achieve energy-saving and emission reduction become the keys of soil-source heat pump system technology. Therefore, we took the soil-source heat pump system of a business building in Jiangsu as typical object of study and presented test results for different working conditions. According to the test results, an analysis of the operation characteristics under different working conditions was given. The auther also established an U-tube ground heat exchanger model and verifies the reliability of the test results via the method of simulating calculation by Fluent.In the experiment, at first the writer took a research and analysis on ground thermal response test system and introduces the fundamental principles, equipments and specific steps of field testing method. According to field test method of ground thermal response we tested in Yangzhou, we got the data of initial temperature, thermal properties of underground soil and the heat exchange amount of unit length tube. At the same time, this paper carried out a comparative study of both double and single U-tube underground tubes. These data can be considered as references to the optimization design and operational guidance of ground-source heat pump systems in Jiangsu, and they provide parameters to the simulation by Fluent software as below.Then, different operating conditions ground-source heat pump system were tested on an office building in Yangzhou. According to the test results, the writer analysed the effects of air conditioning, the system’s efficiency, heat transfer characteristics of underground tubes, and the recovery properties of the temperature field near the underground tubes under different working conditions. The author achieved a conclusion that under the same operation condition, when the system is steady, appropriately reducing the pump frequency and rate of flow of the ground source side not only reduces the room air conditioning effect, but also reduces the total power of the system. The system’s average COP increases from 2.78 to 2.9, the heat exchange amount of unit length tube increases by 5.2%. And it slows down the rise of soil temperature to a certain extent, this is good to improve the resilience of the soil and the heat exchanger efficiency of the buried pipe.On the other hand, under the guarantee of human comfort,we adopted the operation mode with 4:1 run-stop ratios compared to the normal operation mode.The test results showed that the heat exchange amount of per meter tube increased by 10% and the average COP system increased by 30%. Meanwhile, intermittent operation mode has the ability to control the rise of the soil temperature around the buried pipes. And this mode is beneficial to the improvement of the resilience of the soil and the heat exchanger efficiency of the buried pipes. Last but not least, in the cast of partial operation, the soil temperature of regions with run-stop mode has a better recovery ability. This mode improves the using rate of geothermal energy and is also conducive to the heat exchanger running with a steady and efficient condition.In the aspect of simulation, the paper was established a quasi-three-dimensional model of unsteady state heat transfer of buried tube heat exchanger temperature field by the software Fluent. The auther compared simulation results carried out by the built model with research data of other literatures, and the maximum relative error is only 1.4%, then validated the correctness of the buried tube heat transfer model. Besides, the paper simulated the soil temperature field of buried heat exchanger. The results showed that the soil temperature field around heat exchanger under summer different operation conditions compared with the value of simulation, the relative error was 2.75%. This suggested that the simulation results fit well with experimental data and verified the correctness of the test results.