Contrastively Heat Performance And Economical Research Of Single U-pipe And Double U-pipe Borehole Heat Exchangers

With the development of economy and the growth of population in the world, energy and environmental issues have become a huge problem. Ground coupled heat pump system which is sustainable, energy-saving, environmental friendly and economical has drawn widespread attention. A research on the heat performance and economy of single U-pipe and double U-pipe borehole heat exchangers was made in this thesis based on a project of ground heat pump.A contrastively research on the heat performance of single U-pipe and double U-pipe borehole heat exchangers based on a single set of borehole was carried out in this thesis, which analyses the impact backfill material, inlet temperature of exchangers, radius of boreholes, mass flow rate, depth of boreholes, pipe diameter and thermal properties of earth have on the heat performance of exchangers. And differences between the two exchangers was mainly focused on.The heat interaction of multi-boreholes was taken into consideration in this thesis to analyze the impact multi-boreholes have on the exchangers based on the project of ground heat pump, after which the temperature around boreholes and the impact arrangements on the exchangers were analyzed and the arrangements of multi-boreholes were optimized in the thesis.Based on the study above, a temperature response modeler under the circumstance of annual hourly load and a mathematical mode of heat pump was established which uses annual dynamic load of the building as input parameter. Then the heat performance under the circumstance of dynamic load was simulated by the program of single U-pipe and double U-pipe borehole heat exchangers based on the coupling of the temperature response modeler and ground heat exchanger model. After the simulation, inlet and outlet temperature of the heat exchanger, COP of heat pump, heat exchange capacity by unit and temperature distribution of borehole wall can be obtained under the circumstance of dynamic load.A control system for refrigerating plant room for this ground heat pump projiect was introduced which included the fuzzy control theorem and the variable frequency speed regulation technology for water pumps. Then the capital composition of ground coupled heat pump system is analyzed and economical model are presented. The efficiency and annual cost of heat pump system can be attained by the stimulation of various schemes of single-U and double-U ground pipe exchangers. Based on the annual cost, a contrastively research on economics and optimization of various schemes is made.