Dynamic Characteristic Analysis And Performance Optimization Of Double-Effect LiBr Absorption Refrigeration Chiller

Lithium bromide absorption chillers are driven by low-grade heat energy and provide refrigerant water for cooling,which is widely used in integrated energy systems.Usually the lithium bromide absorption chiller is arranged at the end of the system,and the performance is affected by the upstream parameters and user-side parameters.Therefore,this article takes the series double-effect lithium bromide absorption chiller as the object to study its operating dynamic characteristics and meet the needs of user-side cooling At the same time,optimize parameters to improve energy efficiency.Using FORTRAN language and referring to relevant literature,the physical property calculation module of lithium bromide aqueous solution was compiled.The model of 7 heat exchange parts including absorber,evap orator,condenser,low-pressure generator,high-pressure generator,low-temperature heat exchanger and high-temperature heat exchanger was completed,and the dynamic operation program was compiled.The program runs on the high-performance computing platform through the dynamic link library dll file.Under the same initial parameters,the error between the simulation results of the built double-effect lithium bromide absorption refrigeration system and the design results is less than 1.15%.The step disturbance dynamic simulation test of heat source steam temperature(pressure),cooling water inlet temperature and flow rate,refrigerant water inlet temperature and flow rate was carried out,and the dynamic response curves of cooling capacity,evaporation pressure,refrigerant water outlet temperature and refrigeration coefficient were analyzed.The simulation results show that the order of the impact on the performance of the unit is the refrigerant water inlet temperature,cooling water temperature,cooling water flow rate,refrigerant water flow rate and heat source steam temperature.The inlet temperature of the refrigerant water increases by 1 ℃,the cooling capacity increases by 13.80%,and the cooling coefficient increases by 4.78%.During the operation of the system,properly increasing the return temperature of the refrigerant water can effectively increase the cooling capacity and coefficient of the system.In order to further obtain the optimal operating conditions of the system,when other parameters remain unchanged,126 kinds of combination parameters are randomly selected,and optimization algorithms are used to analyze the effect of t he combination parameters on system performance.The gravitational search algorithm is used to optimize the cooling capacity and coefficient of the system for single-objective optimization and multi-objective optimization.The results show that when the cooling capacity and the cooling coefficient reach the maximum values of5199 k W and 1.35,the corresponding operating conditions and disturbance analysis are the same.Using this combined parameter adjustment can improve the system’s operating efficiency.If the user has requirements for the cooling capacity and the cooling coefficient,they can also find the best operating conditions according to the designed weight ratio.