| Direct-fired lithium bromide(Li-Br)air-conditioning system is one of the commonly used forms of air-conditioning systems in China.As the working years of the system increase,the cooling capacity of this type of refrigerator has attenuated significantly,and most systems are not optimized for energy saving during operation,resulting in a gradual increase in energy consumption and a gradual deterioration in the thermal comfort of the room.In order to solve the problem of attenuation of cooling capacity of direct-fired Li-Br units and improve operating efficiency,this thesis proposed several different transformation and operation optimization schemes for the common problems of direct-fired Li-Br air conditioning systems.At the same time,based on the TRNSYS simulation software,the original system and the modified system simulation models were established.Through simulation comparison,the problem of poor thermal comfort in the room and increased operating energy consumption of the air conditioning system due to performance degradation of the direct-fired Li-Br unit were initially solved.An office building equipped with the direct-fired Li-Br air conditioning system in Wuhan was selected in this thesis as the research objective.Based on on-site investigation and actual measurement,the cooling/heating attenuation of the direct-fired Li-Br unit of the system was analyzed.At the same time,this article used the sample data provided by the manufacturer to establish the mathematical model of the direct-fired Li-Br unit through the polynomial fitting method.Then the corresponding unit module on the TRNSYS software based on the mathematical model was developed.And this module was used to build a simulation model of the original air-conditioning system of the building.Through the simulation analysis of the original air-conditioning system,it was found that the original air-conditioning system can meet the thermal comfort requirements of air-conditioned rooms in winter,but the thermal comfort of air-conditioned rooms in summer is poor.In order to solve the problem of poor room thermal comfort caused by the attenuation of unit cooling capacity,this thesis proposed two transformation routes.Through simulation,comparing and analyzing the effects of different retrofit schemes in terms of system energy consumption,economy,and environmental benefits,the best retrofit scheme was finally reached by the usage of additional air source heat pumps to make up for the lack of cooling capacity of the original system Li-Br unit.Aiming at the operation optimization problem of the direct-fired Li-Br air-conditioning system,this thesis proposed an operation optimization scheme by the variable-frequency control of the water pump and the variable supply chilled water temperature control of the Li-Br units.When the water pump was running with variable frequency,the energy saving rate of the water pump is 60.28%,the annual energy consumption of the system is reduced by 10.23%,and the SCOP is increased by 11.39%.When operating with variable chilled water temperature,the best variable chilled water temperature operating program was achieved by adjusting the chilled water supply temperature based on the change in the system’s partial load rate.Compared with the system before optimization,the optimized system has an annual energy saving rate of11.73%,and SCOP has increased by 13.29%. |
