Software Development And Optimization Design Of Hybrid Ground Source Heat Pump System With A Gas Boiler

Under the premise of the government promoting renewable energy vigorously,ground source heat pump(GHSP)system has been widely used because of both clean and efficient advantages.However,the development of this technology is hindered by some factors such as high initial investment,difficult construction process of ground heat exchangers(GHEs)and imbalanced underground heat transfer.The new energy saving technology of hybrid ground source heat pump with gas boiler as the heat auxiliary can effectively reduce the initial investment and solve the problem of underground heat imbalance.The heat transfer model of the GHEs is very complicated,and the influential parameters are very large.The length of the buried pipe cannot be calculated by manual calculation.The use of special software for the heat transfer analysis and simulation of GHEs has reached a consensus in the field of GSHP engineering.This dissertation mainly introduces the software development and optimization design process including the software interface and results analysis of the design/simulation for the hybrid GSHP system with the auxiliary gas source boiler.The developed software of hybrid system is based on the design simulation software "geothermal star" which has been developed by the GSHP institute of Shandong Jianzhu University and uses Visual Studio 2010 development platform to adopt visual design simulation software compiled by VC ++programming language.The keypoint of the hybrid GSHP system design is to determine the reasonable ratio of the building loads allocated to the two heat supply systems(GSHP and gas boiler)which can make sure the underground thermal balance.Therefore,the building load has been first analyzed and the baseline of the building load which is beared by ground heat exchanger has been caluclated with the given thermal unbalance rate.Two strategies to control the start and stop of the gas boiler was considered in the software for the hybrid GSHP compound system with gas-fired boiler: one is the time control,another is the load control.The monthly design method and the hourly simulation method of the hybrid GSHP system is also developed.The curves and data tables of parameters such as the desgined buried pipe length,soil temperature,heat pump inlet and outlet temperatures,system energy consumption,heat transfer per borehole and so on are also presented in the design and simulation results.Finally this dissertation disscussed the economics of the auxiliary gas source boiler and the reliability of the software according to the actual project.The comparison results between the measured data and the simulated data demonstrates that the gas boiler can effectively reduce the peak-load of the GHE,reduce the designed length of the buried pipe,solve the problem of underground thermal imbalance and improve the efficiency of the unit.Meanwhile,it can be seen that the heat transfer model of the GHEs is accurate and the calculation results of the developed gas boiler auxiliary GSHP compound system is accurate.The software can simulate the operating conditions of the composite system for a long time,which can provide both theoretical support and technical guidance for both research and engineering application of the hybrid GSHP system in the future.