Research On Energy Saving Optimization Operation Of Central Air-conditioning Water System Based On TRNSYS

With the rapid growth of economic and social development and the rapid growth of public building area,the total energy consumption of buildings will continue to increase.According to statistics,the energy consumption of central air conditioning accounts for about 50% of the total energy consumption of the building,and the energy consumption of central air conditioning water system accounts for about 30% of the total energy consumption of the refrigeration room.Therefore,the optimization of the water system is of great significance for the energy saving and consumption reduction of the whole air conditioning system,and it is an important way to improve the energy efficiency ratio of refrigeration room systems of public buildings and achieve the goal of "peak carbon dioxide emissions,carbon neutrality".Based on the operation data of the actual office buildings in Qingdao,it is found that in the actual operation of the central air conditioning water system,the energy efficiency of the equipment,pipeline resistance,operation strategy and other aspects need to be further optimized.Therefore,this paper takes an office building in Qingdao as the research object,establishes the simulation platform of central air conditioning water system by TRNSYS software,explores the energy-saving effects of three optimization schemes,namely the application of permanent magnet synchronous motor,synchronous variable frequency operation of parallel pumps and parallel operation of cooling tower,and completes the analysis of the overall optimization of central air conditioning water system on this basis.The main work is summarized as follows.(1)From the theoretical level,the feasibility analysis of four energy-saving technologies is completed,namely,the application of permanent magnet synchronous motor,synchronous variable frequency operation of parallel pumps,resistance optimization of water system,and the adjustment of the number of running units of cooling water tower.(2)Based on the actual building,the TRNSYS load simulation platform was built.The simulation results showed that 43% of the time the air conditioner operated under50% load rate,and 56% of the time it operated between 50% and 90% load rate.(3)The simulation platform of central air conditioning water system was built.The energy consumption simulation of the original refrigeration room showed that the energy consumption in the whole refrigeration season was 207950 k Wh.The COP of the chiller stayed around 6.5 in July and August,and the average EER of the refrigeration room was 4.6.COP of chiller remained around 7.0 in September,and average EER of refrigeration room was 4.9.(4)The application of permanent magnet synchronous motor,synchronous frequency conversion operation of parallel pumps and parallel operation of cooling towers are simulated and analyzed respectively.Applying permanent magnet synchronous motor to water pump,the energy saving of chilled water pump is2.2%～9.7%,and the energy saving of cooling water pump is 4.2%～12.2%.When the parallel pumps synchronously frequency conversion operation,check valves can be removed to optimize pipeline resistance and equipment selection.Combined with the high efficiency of permanent magnet synchronous motor under low load,the energy consumption of chilled water pumps can be reduced by 23.2% to 28.4%,the energy consumption of cooling water pumps can be reduced by 24.4% to 36.1%,and EER can be increased by 0.3 to 0.5.The parallel operation of the cooling water tower increases the heat exchange area of the cooling water tower,which can reduce the return water temperature of the cooling water,and improves the COP of the chiller accordingly.The maximum energy saving can be 2.75% under each working condition.(5)Combined with the actual engineering transformation project,the verification of two energy saving schemes of permanent magnet synchronous motor and parallel pump with synchronous frequency conversion was completed.In the engineering example of permanent magnet synchronous motor,the energy saving rate of the modified water pump reaches 7.4%.In the application of parallel pump synchronous frequency conversion engineering example,the energy saving of the pump after the transformation reaches 5641 k Wh,and the energy saving rate reaches 24.8%.(6)Combined with a variety of schemes to optimize the central air conditioning water system.Based on the particle swarm optimization algorithm,the optimal operating parameters of refrigeration room under different load rates under the overall optimization scheme were solved.The optimization results are applied to the central air conditioning water system simulation platform after overall optimization.In the whole cooling season,the overall optimization scheme reduced the energy consumption of chilled water pump and cooling water pump by 28.1% and 32.4%,respectively,and the energy consumption of refrigeration room was reduced by 28972 k Wh,and the average EER of the optimized was up to 5.6.This paper proposes an overall optimization scheme for the central air conditioning water system,which has remarkable energy-saving effect,EER of refrigeration room system and COP of chiller are significantly increased,and this scheme has certain guiding significance for the design and energy-saving transformation of refrigeration room.