Numerical Simulation And Optimization Of Composite Adsorbent Tube Adsorption Refrigeration System

As a kind of refrigeration,adsorption refrigeration system can use low grade energy and green refrigerant.The system has good anti-vibration and stability.After decades of development adsorption refrigeration,it has gained more and more attention.At present,there are still some distance between the adsorption theory and practice.The research focus on this stage is to shorten the cycle time,improve SCP and energy efficiency of the system.Through the numerical simulation of adsorption process,it can directly reflect the heat and mass transfer in the adsorption bed under different conditions to provide a theoretical basis for the design and optimization.This article studies Numerical Simulation of adsorption bed based on the analysis of the present situation,summary on the kinetic model commonly used.To research on improving the adsorption bed chemical adsorption kinetics model and optimal design,using calcium chloride/graphite composite adsorbent expansion tube filled adsorption refrigeration system as the research object,a physical model and the mathematical model of single bed adsorption refrigeration system have been established.Numerical simulation analysis use MATLAB software,it has some guiding significance for practical engineering application and optimization design of the law,and summed up the specific methods of optimization design.The adsorption kinetic model based on considering the actual changes of adsorbent porosity,thermal conductivity and other parameters,this article establishes the mathematical model of single adsorption bed.Based on the numerical simulation under different conditions of single tube adsorption bed process,variation of parameters such as temperature,pressure,adsorption quantity,SCP of adsorption bed has been obtained.The diameter of adsorption bed is longer,the adsorption time is more;the evaporation pressure is higher and the cooling temperature of adsorption bed is lower,the complete adsorption reaction time is shorter;the cooling temperature under the same evaporation pressure is higher adsorption maximum average temperature in the bed is higher,but in the end it will get closed with cooling temperature;the adsorption reaction process in adsorption bed pressure has no obvious changes and fluctuations are in a very small range;enhance the evaporation pressure,lower cooling temperature and smaller diameter can improve the adsorbent bed's SCP.Through the study of a single tube adsorption bed on desorption process,we can fit kinetic parameters of absorption process and give the kinetic model of calcium chloride/graphite composite adsorbent desorption.For single tube adsorption refrigeration system we designed,simulated COP changes under different conditions.With the rise of the condensing temperature,COP drops,but the influence of the condensing temperature is very small;with the temperature of adsorption cooling system rising,COP increases;with heat source temperature increasing,COP first increases and then decreases;with the increase of the diameter of the adsorption bed,COP increases first and then decreases.Next analysis of metal loss to total heat loss ratio in different conditions indicates that,with the adsorption cooling temperature rising,heat consumption ratio decreases;with the heat source temperature rise,metal heat consumption ratio is first decreased and then increased.At the same time the article gives the reason why metal heat consumption ratio influence system COP changes.It has certain guiding significance for the design of adsorption bed and system.The reasons why SCP and COP can't be improved at the same time are analyzed.Established a multi-objective optimization function and changed the objective function according to the change of weight coefficient to suit different adsorbent bed and then get the optimal adsorption bed size by the given conditions.On this basis,this paper presents the curve of COP with the change of the adsorption bed diameter in a given design condition and the adsorption bed size,SCP,COP when the weight coefficient were 0.2,0.5,0.8.