Finite Time Thermodynamics Optimization Of Indirect Sewage Source Heat Pump System

At this stage,countries all over the world are paying great attention to energy and environmental issues,and are looking for new and clean renewable energy sources.Urban sewage has been widely used in actual projects because of its environmental protection and high efficiency and energy saving characteristics.However,in the actual operation of the sewage source heat pump system,its operating effect is often affected by many factors.Therefore,the optimal design of the sewage source heat pump system and the selection of the best operating conditions are particularly important.This article uses the limited time thermodynamics Methods To optimize the indirect sewage source heat pump system.First,the indirect sewage source heat pump system of a hotel in Beijing was selected as the research object to investigate the winter operation of the system and collect relevant parameters.The data included sewage temperature,hot water temperature,heat supply,energy consumption,and COP(coefficient of performance).Organize system operating data and explore the relationship between sewage inlet temperature,temperature difference between inlet and outlet and system performance.Secondly,the indirect sewage source heat pump system is optimized by using the theory of finite time thermodynamics.First,the heat leakage,thermal resistance and the irreversibility of the cycle are considered,and the sewage source heat pump cycle model is constructed,and then the Lagrangian multiplier method is used to calculate The objective function is optimized to study the proportional relationship between the heat transfer areas when the heat pump heating performance coefficient is the best;the relationship between the parameters when the total heat transfer area of the heat exchanger is the smallest.Finally,the optimization results are verified by specific calculation examples,and the results show that a reasonable selection of the heat transfer area of the heat exchanger can effectively improve the operating performance of the system and can also reduce the initial investment of the system.Then use TRNSYS software to build a simulation model of the indirect sewage source heat pump system,simulate the original system and the optimized system respectively,and analyze the changes in the hot water temperature,heat supply,energy consumption and COP produced by the two systems.The simulation results show that when the simulation time is January 15,2020,the hot water temperature,heating capacity,and COP produced by the optimized system are increased by 11.78%,28.33%and 18.42%than the original system,and energy consumption is reduced by 15%.%.When the simulation time is the whole year of 2020,the total heat supply of the optimized system and the original system are 4.44GW·h and 3.51GW·h,respectively.The total heat supply of the optimized system is 26.50%higher than that of the original system.The annual energy consumption of the optimized system and the original system are 0.95GW-h and 1.1 1GW·h,respectively.The optimized sewage source heat pump system saves energy by 14.41%compared with the original system.Finally,from the energy quality point of view,the exergy analysis of the two systems is carried out,and the optimized sewage source heat pump system has an exergy efficiency 25.88%higher than that of the original system.The optimized indirect sewage source heat pump system is comprehensively evaluated from the three aspects of energy saving,economy and environmental protection.Among them,the primary energy saving rate of the optimized system is 14.63%higher than that of the original system,the standard coal saving is increased by 57.58%,and the cost is increased.The annual value has been reduced by 16.16%,and the total emission reduction of pollutants has increased by 36.54%.Therefore,it can be seen that the comprehensive performance of the system after a finite time thermodynamic theory optimization has improved,and the optimization effect is significant.