Study On Optimization Of Adsorption Bed Structure Of Silica Gel-water Adsorption Refrigeration System

With the continuous growth of the global population and the continuous progress of society,the massive use of fossil fuels has caused increasingly serious environmental pollution problems.Traditional vapor compression refrigeration technology needs to be driven by more electrical energy,and uses non-environmentally friendly refrigerants such as chlorofluorocarbons(CFCs)and hydrofluorocarbons(HCFCs)to consume the ozone layer and cause global warming.Adsorption refrigeration technology uses low-grade thermal energy as the driving energy source,which has the characteristics of no pollution and energy saving,and has attracted much attention in the past 20 years.However,there is still a certain distance between the adsorption refrigeration unit and large-scale commercial use.The main reason is that the adsorbent has poor thermal conductivity,the contact area between the adsorbent and the bed metal is small,there is a large contact thermal resistance,and the refrigerant gas flow process There is also a certain mass transfer resistance in the process of adsorption and desorption.In order to carry out research on the heat and mass transfer process of the adsorption bed of the silica gel-water adsorption refrigeration system,this paper builds a physical and mathematical model of the finned tube adsorption bed,realizes the dynamic simulation of the adsorption/desorption process,clarifies the adsorption bed structure parameters and cycle period,etc.For the impact on the performance of the refrigeration system,the simplex optimization algorithm is used to optimize the adsorption bed structure parameters and cycle period to comprehensively improve the system performance.The main research contents of this article are as follows:(1)Firstly,a model of silica gel-water working fluid to single adsorption bed is constructed,and the heat and mass transfer,adsorption and desorption processes in the adsorption bed are studied in detail through numerical simulation methods.The influence rules of the fin structure parameters and cycle period on the performance of the adsorption refrigeration system are obtained.The research results show that:using shorter fin height,spacing and cycle period is beneficial to lifting the system SCP,while the fin thickness has little effect on SCP By increasing the fin thickness twice,the system SCP value will only increase slightly;in order to improve the system COP,shorter fin height,proper fin spacing,thinner fin thickness,and longer cycle period should be used;The use of long,thick fins,larger fin spacing,and shorter cycle period is beneficial to improve the adsorption refrigeration system TCP.(2)By designing the L16(45)orthogonal experiment and analyzing the experimental results using the analysis of variance,the degree of influence of the fin height,fin spacing,fin thickness,and cycle period on the performance of the adsorption refrigeration system is clarified,and the optimal design scheme is selected.Variance analysis of the orthogonal experiment results shows that:fin height and cycle period are the two most important factors affecting SCP among the four factors,contributing 48.60%and 26.43%respectively;cycle period and fin thickness affect COP The two most important factors,the contribution levels are 55.7%and 27.54%respectively;the fin height,cycle period,and fin spacing have a significant impact on the system TCP,and the contribution levels are 49.97%,35.75%,and 14.24%,respectively.Through the optimal combination of orthogonal experiments,the optimal SCP,COP and TCP of the system are 161.12W/kg,0.613 and 0.173W respectively.(3)In order to further improve the comprehensive performance of the silica-water adsorption refrigeration system,the linear weighting method is used to integrate the three evaluation index functions of SCP,COP and TCP into an optimization objective function.During the optimization process of the adsorption bed structure,ensure SCP,COP and TCP It has the same importance in the optimization process.The finite element analysis method and the Nelder-Mead simplex optimization algorithm are used to carry out related research to obtain an adsorption bed design scheme that can keep the system SCP,COP,and TCP at a high level.The optimization results show that the simplex optimization calculations with SCP,COP,and TCP as the optimization objective functions respectively require:29,68,and 78 iteration processes to obtain the optimal solution,and the optimal solution values are:164.53W/kg,0.620,0.307W.The optimization process with the weighting function as the goal requires 49 simplex iterations,the optimal value is:2.08,the corresponding system SCP,COP,TCP values are:148.14W/kg,0.532,0.098W,the corresponding four factors are taken The values are:cycle period 1082.85s,fin height 10.83mm,fin spacing 2.24mm,fin thickness 0.4mm.Thus,through weighted function optimization,an optimized design scheme for an adsorption refrigeration system with high energy utilization rate,large refrigeration power,and sufficient refrigeration capacity is obtained.In conclusion,by analyzing the adsorption/desorption process in the adsorption bed of the adsorption refrigeration system,the influence of the structure parameters of the adsorption bed and the cycle period on the performance of the system is studied in this paper.Further,taking the linear weighting function of the three performance indexes SCP,cop and TCP of the refrigeration system as the optimization objective,the refrigeration system is carried out by combining the finite element method with the simplex optimization algorithm Optimization and improvement,the optimal design of adsorption refrigeration system is obtained,which provides theoretical basis for the optimal design of silica gel water adsorption refrigeration system.