Study Of Thermal Characteristics And Economical Efficiency Of Single-U And Double-U Ground Pipe Soil Source Heat Pump System

This thesis presents initially the system of the soil source heat pump which is not only an air-conditioning method of the energy conservation and the environmental protection, but also to possess merits of the reliability, stability and economical efficiency. It is a sustainable developing new technology of the building energy saving. The thesis also demonstrates the advantage of the vertical underground pipe heat exchanger system, the economical efficiency of the Single-U and the Double-U soil heat exchangers is analyzed strongly. The major study is organized as follow:1. Analyzes the influence factors of ground heat exchanger system and existed questions in design and construction of ground source heat pump engineering, introduces the principle and structure of the movable geo-thermal response test apparatus. Take a real engineering as example, illustrates the method and step of geo-thermal response test, obtains the in-situ undisturbed far-field ground temperature and inlet and outlet temperature response curve of ground heat exchanger. Through the line-source theory, gets the borehole thermal conductivity and thermal resistance. Gives the effect of different factors to geo-thermal response test for example: heat damage and plus between test apparatus and environment, test durance time, power supply stability, undisturbed ground temperature, variety of ground thermal conductivity along the length of borehole and ground water flow.2. To compare the characteristics of the heat transfer between the Single-U and Double-U soil source heat pumps, the heat exchanging models of the Single-U and Double-U underground pipe heat exchangers have been established. The influences of each kind of factor to the underground heat exchanger are analyzed. It not only considers the characteristics of the heat transfer between pipes and wells, but also can analyze the phenomena of heat circumfluence between pipes within the well. These performances have established the theoretical fundamental for the study of the economical efficiency of the Single-U and Double-U underground pipe heat exchangers.3. In order to validate the heat exchanging model, one year tracking test is carried out for the project which were installed Single-U and Double-U ground heat exchanger in the office building of Tianjin Shengxing Furniture Corporation. Under the typical working situations, the simulated results and testing data have been compared in the numerical value and varying trends. The results agreed well with the model. Therefore, the validity of the model has been testified.4. The concept of the cost of the quantity of well-depth heat exchanging per unit Clq has been introduced. It is showed the ratio of the total investment of the well-depth per unit Cl to the quantity of the well-depth heat exchanging ql. It is an economic indicator to reflect the investment cost and the characteristics of the heat-exchanging. According to the model analysis of the heat exchanging characteristics of the Single-U and Double-U ground pipes under the varied working conditions, the corresponding values of Clq have been compared. The results indicate that the Double-U type is more superior economy than Single-U type.Based on the actual engineering projects, the benefits of the environmental protection and the energy saving of the soil source heat pump air conditioning system have been validated. Differentiates and advantages of the soil source heat pump and the underground water heat pump are given.