Analysis And Research For The Performance Of Hybrid Ground Source Heat Pump In Region With Hot Summer And Warm Winter

Ground source heat pump system(GSHPS)with the characteristics of its high efficiency,environmental friend and energy saving has been widely applied in various areas.In hot summer and cold winter regions such as Shanghai,the cooling load in summer is greater than the heating load in winter.During long-term operation,the thermal condition of soil around the ground heat exchanger(GHE)can be degraded by the thermal imbalances,and resulted in the overall performance of GSHPS reduced.A hybrid ground source heat pump system(HGSHPS)is proposed to overcome thermal imbalance under degraded ground thermal conditions by incorporating the GSHPS with a cooling tower or a heat recovery system for extra heat rejects.The auxiliary equipment in the GSHPS will equilibrate some portion of the heat rejection to reduce the cooling load imposed on the GHE.Taking the reconstruction project of a hotel in Shanghai as the research object,this thesis designed a hybrid ground source heat pump system,combined with waste heat recovery based on the reality of climatic characteristics and the hot-water demands of building functions.In order to ensure the efficient and stable operation of GSHPS,to obtain the optimum ratio of heat recovery,the performance of conventional ground source heat pump system and hybrid ground source heat pump system with the ratio of waste heat recovery was 18%,30% and 53%,respectively,was analyzed.Taking into account the part load,the author established a heat pump model with variable conditions by adding part load rate and fraction of full load power,to adjust its forecast performance of non-design condition corresponds to the actual operating conditions.The transient simulations were carried out for a period of 20-year by setting control card,which mainly were used to analyze the impact on thermal balance problem,coefficient of performance and energy consumption with different ratios of waste heat recovery.The results showed that increasing the heat recovery ratio can mitigate the heat stack of soil significantly;however,the energy consumption in the whole life cycle is not proportional to the ratio of waste heat recovery.After 20-year operation,the thermal imbalance of scenario 4 is approximately 5.2%,the elevated temperature is 0.34?.The energy consumption of scenario 4 increases by 2.2% compared with that of the scenario 1.As a result,there is never a situation that can get the best thermal balance condition and the minium energy consumption of system at the same time when optimizing the ratio.Thus,an economic performance of operational cost and supply cost of domestic hot water should be analyzed.In the whole life cycle,an economic performance of initial investment,operational costs and producible costs of domestic hot water for different scenarios of GSHPS had been analyzed using the dynamic annual cost method.The results showed that when the ratio of waste heat recovery is 53%,the dynamic annual cost of GSHPS is the minimum and achieves the optimizing energy-saving effect.Compared with scenario 1,the dynamic annual cost of scenario 4 reduces by 52.7%.In addition,an exergy analysis of the system,which has the optimum ratio,was carried out to determine the exergy loss and the efficiency of each component and the overall system.The thesis demonstrated that a HGSHPS,combined with waste heat recovery,can reduce the exergy loss of codenser and evaporator.The exergy loss of the compressor is the maximum.