Research On Optimization Of Ground-coupled Heat Pump Systems Under Specific Constraint Conditions

Ground source heat pump (GSHP) has been widely used in the field of HVAC andbuilding energy efficiency as a new type of technology which is energy-efficient andenvironment-friendly. Since a large number of design parameters will be involved inGSHP systems, the optimum combination of different parameters is a key to ensure highefficiency. Relevant subjects related to ground coupled heat pump (GCHP) systems arediscussed in this paper. The research is focused on four parameters including totalborehole number, borehole depth, borehole space and the mean velocity of fluid inU-tubes.This paper considers three constraint conditions related to the total flow rate of fluidin ground heat exchangers, the limit on fluid temperature and the area of available land.Then the relationship between different design parameters is analyzed. The problem offinding the optimum combination of four design parameters is transformed into anoptimization problem in which the total borehole number is chosen as single decisionvariable. Some case study is carried out through dynamic simulation.An office building in Shenyang is modeled and the corresponding characteristic ofbuilding load is analyzed with the aid of DeST. The physical model of a GCHP systemfor that building is built in TRNSYS. Then the equivalent annual cost (EAC) of theGCHP system is chosen as the object function in order to perform economic analyses andtherefore conduct a research on optimization problems. The influence of designparameters on system performance is studied. In addition, reliability of the system underadverse operating conditions is also discussed. According to results of simulation, thetotal borehole number will have a certain influence on both initial costs and operating costs of the GCHP system under specified constraint conditions mentioned in this paper.And it is important to consider the relationship between initial costs and operating costsin the design process. An optimum combination of four parameters could be found aftercomparing several feasible design schemes and will, in turn, lead to the lowest EAC. Theoptimization method proposed in this paper could be utilized by engineering designers forreference purposes.